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DEPARTMENT OF MARINE AND FISHERIES SCIENCES 
UNIVERSITY OF GHANA 
 
Evaluation of Farm-Made and Commercial Fish Diets for Hapa Culture 
of Nile Tilapia (Oreochromis niloticus L.) in Ghana 
 
Francis Assogba Anani 
(10120933) 
 
 
 
This thesis is submitted to the University of Ghana, Legon in partial fulfilment of the 
requirement for the award of PhD Fisheries Science degree.  
 
 
 
March, 2015 
 
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DECLARATION 
This thesis is my own work produced from research undertaken under supervision of: 
 
 
………………………………………… 
        FRANCIS ASSOGBA ANANI 
                 (CANDIDATE) 
 
 
 
 
………………………………………… 
   PROF. FRANCIS. K.E. NUNOO 
      (PRINCIPAL SUPERVISOR) 
 
 
 
 
………………………………………… 
PROF. MATILDA STEINER-ASIEDU  
           (CO-SUPERVISOR) 
 
 
 
 
………………………………………… 
        DR THOMAS N.N. NORTEY 
                 (CO-SUPERVISOR) 
 
 
 
 
………………………………………… 
         DR NELSON W. AGBO 
           (CO-SUPERVISOR) 
 
 
 
 
 
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ABSTRACT 
One of the major constraints to aquaculture development and expansion in Ghana is 
affordable nutritionally balanced and cost effective fish diet. Although some fish farmers 
produce their own farm-made fish diets, these diets do not meet the nutritional 
requirements of the cultured fish as the farmers do not follow the appropriate feed 
formulation protocol. This study was carried out to generate information on the 
commercial fish diets and feed ingredients currently used by small-scale pond fish 
farmers in five major pond fish farming Regions (Ashanti, Brong-Ahafo, Central, Volta 
and Western) in Ghana. Six of the commonly used ingredients by the farmers were 
selected and used to formulate and prepare farm-made tilapia diets which were evaluated 
against two commonly utilised commercial tilapia diets for Nile tilapia (Oreochromis 
niloticus). In all, five diets namely A (farm-made diet supplemented with vitamin-mineral 
premixes, lysine and methionine), B (farm-made diet without supplements), C 
(commercial tilapia diet, Coppens), D (commercial tilapia diet, Raanan) and E (mixture 
of B and Raanan in a ratio of 1:1). The first part of the study was conducted in net hapas 
installed in a 0.2 hectare earthen pond over a 140-day growth period at the Aquaculture 
Research and Development Centre (ARDEC), Akosombo. O. niloticus with an initial 
mean weight of 22.8 ± 2.1 g were stocked at a density of 2 fish m-2 and fed at 4-3 % body 
weight three times a day. The second part of the study involved digestibility of the diets 
and this was carried out in plastic tanks with 20 L of water each for 20 days. After the 
culture period, the final mean weights of O. niloticus were 140.3 ± 23.4, 131.0 ± 24.4, 
148.3 ± 25.4, 187.6 ± 42.1 and 140.7 ± 28.5 g for A, B, C, D and E respectively. There 
was no significant difference (p > 0.05) in specific growth rates among all the dietary 
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treatments. Apparent nutrient digestibility coefficients were high (> 60 %) in all the 
dietary treatments. Crude protein ranged from 77.49 to 87.02 %, crude lipid ranged from 
81.46-93.90 % whilst carbohydrate (nitrogen free extract) ranged from 65.28 to 85.94 %. 
Higher crude protein depositions and lower fat contents were observed in the carcass of 
fish fed farm-made diet A and Raanan. There were no internal and external abnormalities 
in O. niloticus fed with the various diets. Both the farm-made and commercial diets did 
not impact negatively on water quality. In terms of cost-effectiveness, the farm-made 
diets were more profitable than the commercial ones. The results indicated that 
nutritionally balanced farm-made fish diet is cost-effective and will boost growth of 
aquaculture in rural areas where semi-intensive pond aquaculture is mainly practised in 
Ghana. The current fish production (2 500 kg ha-1 yr-1) by Ghanaian small-scale pond fish 
farmers could increase up to a fourfold by using appropriately formulated and prepared 
farm-made fish diets with locally available ingredients. This is likely to increase their 
profit margin to over four hundred percent of what they are making currently using 
commercial fish diets. The costs associated with the use of commercial fish diets by 
small-scale pond fish farmers are high, and in terms of fish growth and economic returns, 
the use of appropriately formulated and prepared farm-made diets will be a better 
alternative. Fish farmers should be trained on the formulation and preparation of 
nutritionally balanced and cost effective farm-made fish diets so as to reduce their 
production cost and increase their profit margin. 
 
 
 
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DEDICATION 
To my wife, Abigail for her perpetual companionship and support. 
 
To my children, Eyram and Likem whose upbringing brings me a sense of responsibility 
at all times. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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ACKNOWLEDGEMENTS 
First and foremost, I am thankful to God, the life giver, whose invisible arms sustained 
and granted me life and valuable insight during this study. 
 
My profound thanks go to the supervisors; Prof. Francis K.E. Nunoo of the Department 
of Marine and Fisheries Sciences (MAFS), Prof. Matilda Steiner-Asiedu of the 
Department of Nutrition and Food Science and Dr. Thomas N.N. Nortey of the 
Department of Animal Science all of University of Ghana, Legon, as well as Dr. Nelson 
W. Agbo of the Department of Fisheries and Watershed Management (DFWM), Kwame 
Nkrumah University of Science and Technology (KNUST), Kumasi for their guidance 
during the study. I am gratefully appreciative to MAFS for given me the opportunity to be 
enrolled as a student for the study. 
 
I am indebted to my employer, CSIR-Water Research Institute for partially sponsoring 
this study. Great appreciation to all my colleagues at the Aquaculture Research and 
Development Centre, Akosombo for their diverse support. To Messrs Kofi Anyan and 
Emmanuel Klubi of MAFS for assisting in the water quality analyses as well as Miss 
Agyari Ohenewaa and Mr. Wisdom Agbeti both of DFWM, for their assistance in the 
Chromic oxide analysis. I wish to express my heart-felt sincere appreciation to all the 
Fisheries Extension Officers in all the Regions where the surveys were carried out for 
their assistance in reaching the farmers and data collection. Finally, many thanks to all 
the fish farmers and other related groups and individuals who gave me their priceless 
attention and perishable time to volunteer the necessary information that built the rock-
hard foundation for this study.  
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TABLE OF CONTENTS 
DECLARATION………………………………………………………………………………....ii 
ABSTRACT……………………………………………………………………………………...iii 
DEDICATION…………………………………………………………………………………...v 
ACKNOWLEDGEMENTS…………………………………………………………………….vi 
TABLE OF CONTENTS………………………………………………………………………vii 
LIST OF FIGURES…………………………………………………………………………….xiii 
LIST OF TABLES……………………………………………………………………………...xiv 
LIST OF PLATES……………………………………………………………………………...xvi 
APPENDICES…………………………………………………………………………………xvii 
CHAPTER 1.0 INTRODUCTION………………………………………………………………1 
1.1 Background Information……………………………………………………………………..1 
1.2 Aim of the Study………...…………………………………………………………………….7 
1.3 Objectives of the Study……………………………………………………………………….8 
1.4 Justification of the Study……………………………………………………………………..9 
CHAPTER 2.0 LITERATURE REVIEW……………………………………………………..12 
2.1 Fish Consumption Patterns in the World………………………………………………….12 
2.2 Contribution of Fish to Human Health and Food Security………………………………14 
2.3 Global Production of Aquaculture………….…………………………………...…………16 
2.4 Aquaculture Growth and Fish Feeding……………………………………………...…….22 
2.5 Production and Use of Fish Feed…………………………………...………………………23 
2.6 Feed Ingredient Production and Availability……...………………………………………24 
2.6.1 Animal Nutrient Sources……………………………………...…………………………..24 
2.6.2 Plant Nutrient Sources…………………………………………………………………....25 
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2.6.3 Microbial Ingredient Sources………...…………………………………………………..26 
2.7 Anti-nutrients in Feed Ingredients………………………………………………………....28 
2.8 Culturing of Tilapia…………………………………………………………………………30 
2.9 Reproduction in Nile Tilapia……………………………………………..…………………30 
2.10 Natural Food and Feeding Habits of Nile Tilapia………………………………………..31 
2.11 Growth of Nile Tilapia……………………………………………………………………..32 
2.12 Use of Formulated Feeds for Nile Tilapia………………………………………………...33 
2.13 Feeding Schedules (Rates and Frequencies) for Cultured Tilapia……………………...34 
2.14 Nutritional Requirements of Nile Tilapia…………………………………………….......35 
2.15 Nutritional Deficiencies in Nile Tilapia…………………………………………………...40 
2.16 Pond Culture…………………………………………..…………………………………...43 
2.17 Use of Hapa in Fish Rearing…………………..…………………………………………..45 
2.18 Hapa-Cum-Pond Culture System………………………………………...……………….46 
2.19 Water Quality in Aquaculture…………………………………………..………………...47 
2.19.1 Water Quality Parameters for Tilapia……………………………………………..…...48 
CHAPTER 3.0 METHODOLOGY…………………………………………………………….50 
3.1 Selection of Study Area for Survey of Fish Feed Ingredients and Commercial  
      Fish Diets……………………………………………………………………………………..50 
3.2 Pre-Survey of Fish Feed Ingredients and Commercial Fish Diets Activities……………51 
3.3 Data Collection………………………………………………………………………………52 
3.4 Selection of Feed Ingredients and Commercial Fish Diets………………………………..54 
3.5 Procurement of Selected Feed Ingredients and Commercial Fish Diets…………………54 
3.6 Storage of Ingredients and Commercial Fish Diets……………………………………….55 
3.7 Determination of the Proximate Compositions of Ingredients and Diets………………..55 
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3.7.1 Moisture and Dry Matter Determination………………………………………………..55 
3.7.2 Ash Determination………………………………………………………………………...56 
3.7.3 Crude Protein Determination…………………………………………………………….56 
3.7.4 Crude Lipid Determination………………………………………………………………57 
3.7.5 Crude Fibre Determination………………………………………………………………58 
3.7.6 Nitrogen Free Extracts (NFEs) Determination………………………………………….58 
3.7.7 Phosphorus Determination……………………………………………………………….58 
3.7.8 Gross Energy (GE) Determination……………………………………………………….60 
3.7.9 Chromic Oxide Analysis…………………………………………………………………..60 
3.8 Study Area for Diet Formulation, Preparation and Evaluation………………………….60 
3.9 Diet Formulation and Preparation…………………………………………………………61 
3.10 Experimental System………………………………………………………………………66 
3.11 Experimental Fish……………………………………………………………………….....68 
3.12 Conditioning and Stocking of Experimental Fish……………………………...………...69 
3.13 Feeding Schedule……………………………………………………………………...……69 
3.14 Measurements of Fish during Growth Study…………………………………………….71 
3.15 Monitoring of Water Quality Parameters………………………………………………..72 
3.15.1 Determination of Water Quality Parameters in the Field……………………………..72 
3.15.2 Determination of Water Quality Parameters in the Laboratory……………………..73 
Alkalinity………………………………………………………………………………………………………………………74 
Ammonia………………………………………………………………………………….74 
Hardness……………………………………………………………………………………………………………………….75 
Nitrates………………………………………………………………………………………………………………………….76 
Nitrites………………………………………………………………………………………………………………………….77 
Phosphate………………………………………………………………………………………………………………………78 
Total Suspended Solids (TSS)……………………………………………………………………………………….79 
3.16 Determination of Biological Parameters………………………………………………….79 
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3.16.1 Growth Performance…………………………………………………………………….79 
3.16.1.1 Mean Weight Gain (MWG)…………………………………………………………...79 
3.16.1.2 Specific Growth Rate (SGR)…………………………………………………………..80 
3.16.2 Survival Rate (SR)……………………………………………………………………….80 
3.16.3 Feed Conversion Ratio (FCR)…………………………………………………………...80 
3.16.4 Feed Efficiency (FE)……………………………………………………………………..81 
3.16.5 Length-Weight Relationship…………………………………………………………….81 
3.16.6 Condition Factor (K)…………………………………………………………………….82 
3.16.7 Energy Retention (ER)…………………………………………………………………..83 
3.16.8 Hepatosomatic Index (HSI)……………………………………………………………...83 
3.16.9 Protein Efficiency Ratio (PER)………………………………………………………….83 
3.16.10 Protein Productive Value (PPV)……………………………………………………….83 
3.16.11 Apparent Digestibility Coefficients (ADC)……………………………………………84 
3.17 State of Fish Health………………………………………………………………………...85 
3.18 Economic Analyses of Diets………………………………………………………………..86 
3.18.1 Incidence Cost (IC)………………………………………………………………………87 
3.18.2 Profit Index (PI)………………………………………………………………………….87 
3.19 Data Analyses………………………………………………………………………………87 
CHAPTER 4.0 RESULTS………………………………………………………………………89 
4.1 Fish Feed Ingredients Used by Fish Farmers in Ashanti, Brong-Ahafo, Central,  
       Volta and Western Region…………………………………………………………………89 
 
4.2 Commercial Fish Diets Used by Fish Farmers in Ashanti, Brong-Ahafo, Central,     
       Volta and Western Region…………………………………………………………………92 
 
4.3 Use of Fish Diets by Fish Farmers in Ashanti, Brong-Ahafo, Central,  
       Volta and Western Region…………………………………………………………………94 
 
4.4 Use of Commercial Fish Diets by Fish Farmers in Ashanti, Brong-Ahafo, Central,  
       Volta and Western………………………………………………………………………….96 
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4.5 Proximate Compositions of Selected Ingredients………………………………………….97 
4.6 Proximate Compositions of Study Diets…………………………………………………...98  
4.7 Experimental Fish………………………………………………………………………….100 
4.8 Growth Performance of Cultured Fish…………………………………………………...100 
4.9 Feed and Nutrient Efficiency of Cultured Fish…………………………………………..105 
4.10 Length-Weight Relationship by Diet Type……………………………………………...107 
4.11 Health Status of O. niloticus according to Diet Type...…………………………………110 
4.12 Body Composition of Cultured O. niloticus……………………………………………..111 
4.13 Cost Effectiveness of the Diets…………………………………………………………...114 
4.14 Water Quality……………………………………………………………………………..116 
4.15 Apparent Digestibility Coefficients of Nutrients in the Diets………………………….120 
CHAPTER 5.0 DISCUSSION…………………………………………………………………122 
5.1 Use of Fish Feed Ingredients………………………………………………………………122 
5.2 Use of Commercial Fish Diets……………………………………………………………..124 
5.3 Use of Fish Diets in the Five Regions……………………………………………………..125 
5.4 Proximate Compositions of Ingredients Used in Diet Formulation and Preparation…128 
5.5 Proximate Compositions of Farm-Made and Commercial Diets……………………….129 
5.6 Growth Performance of the Cultured O. niloticus……………………………………….132 
5.7 Feed and Nutrient Efficiency of the Cultured O. niloticus………………………………135 
5.8 Length-Weight Relationship of the Cultured O. niloticus……………………………….139 
5.9 Condition Factor of the Cultured O. niloticus……………………………………………140 
5.10 State of Health of the Cultured O. niloticus……………………………………………..140 
5.11 Whole Body Composition of the Cultured O. niloticus………………………………...143 
5.12 Effect of the Diets on Water Quality…………………………………………………….145 
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5.13 Apparent Nutrient Digestibility of Diets………………………………………………...145 
5.14 Cost Effectiveness of Diets………………………………………………………………..150 
CHAPTER 6.0 CONCLUSION AND RECOMMENDATIONS…………………………...152 
6.1 Conclusion………………………………………………………………………………….152 
6.2 Recommendations for Research and Policy……………………………………………...157 
6.2.1 Research…………………………………………………………………………………..157 
6.2.2 Policy……………………………………………………………………………………...159 
REFERENCES…………………………………………………………………………………161 
APPENDICES………………………………………………………………………………….206 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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LIST OF FIGURES 
Figure 3. 1 Map showing the five Regions in Ghana (where the survey of fish feed  
                    ingredients and  commercial fish diets were conducted are indicated by  
                    the red spots………………………………………………………………………...51 
   
Figure 3. 2 WRI, ARDEC, Akosombo where the feed trials were conducted……………….61 
Figure 4. 1 Percentage of fish diet types used by fish farmers in Ashanti, Brong-Ahafo,  
                   Central, Volta and Western Region……………………………………………….95  
 
Figure 4. 2 Percentage of fish farmers that used the various types of fish diets in 
                   Ashanti, Brong-Ahafo, Central, Volta and Western Region…………………….95 
 
Figure 4. 3 Percentage of fish farmers using the various types of commercial fish diets  
                   in Ashanti, Brong-Ahafo, Central, Volta and Western Region………………….96 
  
Figure 4. 4 Growth performance of Oreochromis niloticus fed commercial and  
                   farm-made fish diets for twenty weeks……………..……………………………102 
 
Figure 4.5 Weight gain by Oreochromis niloticus fed commercial and farm-made  
                   fish diets for 20 weeks……………………………………………………………..102 
 
Figure 4. 6 Percentage final wet weight distributions of Oreochromis niloticus  
                    fed farm-made and commercial fish diets for 20 weeks………………………..103 
 
Figure 4. 7 Length-weight relationship of Oreochromis niloticus fed farm-made diet A….107 
Figure 4. 8 Length-weight relationship of Oreochromis  niloticus fed farm-made diet B…108 
Figure 4. 9 Length-weight relationship of Oreochromis niloticus fed Coppens…………….108 
Figure 4. 10 Length-weight relationship of Oreochromis niloticus fed Raanan…………....109 
Figure 4. 11 Length-weight relationship of Oreochromis niloticus fed diet E……………...109 
 
 
 
 
 
 
 
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LIST OF TABLES 
Table 2. 1 Anti-nutrient compounds and their biological effects on animals………………..29 
Table 2. 2 Feeding schedules for various sizes of tilapia in semi-intensive and intensive  
                  culture in freshwater ponds………………………………………………………...35 
Table  2. 3 Dietary protein needs for Nile tilapia, Oreochromis  niloticus by life stage…......36  
Table  2. 4 Essential amino acid needs of Nile tilapia, Oreochromis niloticus  
                as % of dietary protein and of  total diet…………………………………………....36 
 
Table 2. 5 Crude lipid, essential fatty acids and energy needs for growth of 
                  Oreochromis niloticus (% dry feed)………………………………………………...37 
 
Table 2. 6 Mineral requirements of Oreochromis niloticus  
                  (% of dry feed except otherwise mentioned)………………………………………38 
Table 2. 7 Vitamin needs of Oreochromis niloticus (% of dry feed except 
                  otherwise mentioned)………………………………………………………………..39 
Table 2. 8 Dietary nutritional deficiency of essential amino acid and essential fatty acid….40 
Table 2. 9 Dietary mineral deficiency signs and symptoms associated with tilapia  
                  species………………………………………………………………………………...41 
 
Table 2. 10 Specific vitamin deficiencies associated with tilapia species…………………….42 
 
Table 2. 11 Water quality tolerance by some commonly cultured fish species……………...48 
 
Table 2. 12 Water quality parameters for tilapia……………………………………………..49 
Table 3. 1 Number of pond fish farmers in Ghana on regional basis in 2011……………….50 
Table 3. 2 Inclusion levels (%) of ingredients used in diets A and B and their cost per  
                  kilogramme…………………………………………………………………………..62 
 
Table 3. 3 Composition of the vitamin-mineral premix used in diet A………………………63  
 
Table 3. 4 Constituent of Coppens (Diet C) as indicated on the label of the feed bag………65 
 
Table 3. 5 Constituent of Raanan (Diet D) as indicated on the label of the feed bag……….66 
 
Table 3. 6  Criteria used at the end of the growth study for fish health observations………86 
 
Table 4. 1a Checklist of utilized fish feed ingredients in Ashanti, Brong Ahafo, Central,  
                    Volta and Western Region of Ghana……………………………………………..90 
 
Table 4. 1b Checklist of utilized fish feed ingredients in Ashanti, Brong Ahafo, Central,  
                    Volta and Western Region of Ghana……………………………………………..91 
 
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Table 4. 2   Checklist of commonly utilized commercial fish feeds in Ashanti,  
                    Brong Ahafo, Central, Volta and Western Regions of Ghana…………………..93 
Table 4. 3 Proximate compositions (% as-fed), gross energy (kJ g-1), phosphorous (%)  
                  and prices (GHS kg-1) of the selected feed ingredients used in the  
                    formulation and preparation of diets A and B….....................................................97 
 
Table 4. 4 Proximate composition (% as-fed), gross energy (kJ g-1),  
                 phosphorous (g kg-1), Chromic oxide concentrations and prices (GHS kg-1)  
                 of Diets A, B, Coppens, Raanan and E……………………………………………...98 
 
Table 4. 5 Percentage deviation of the observed from the expected crude proteins of 
                  the various diets…….................................................................................................100  
 
Table 4. 6 Mean growth performance of the cultured Nile tilapia fed diets A, B,  
                  Coppens, Raanan and E for 20 weeks…………………………………………….104 
 
Table 4. 7 Feed and nutrient efficiency of the cultured Nile tilapia fed diets A, B,  
                 Coppens, Raanan and E for 20 weeks……………………………………………..106 
Table 4. 8 Equation parameters of Length-weight and condition factors for  
                  Oreochromis niloticus fed diets A, B, Coppens, Raanan and E………………….110 
 
Table 4. 9 Whole body proximate composition (%) gross energy (kJ g-1) and  
                  hepatosomatic index of cultured Nile tilapia (mean ± SD)………………………113 
 
Table 4. 10 Cost effectiveness of diets fed to Nile tilapia……………………………………115 
 
Table 4. 11 Summary of statistical analysis of water quality parameters for the various  
                    dietary treatments and the open pond water for a period of 140 days………..116 
 
Table 4. 12 Proximate compositions (%) of faecal samples of Oreochromis niloticus  
                    fed the various diets……........................................................................................120 
 
Table 4. 13 Apparent digestibility coefficients (%) of dry matter, crude protein,  
                    crude lipid, nitrogen free extract, crude fibre, ash, gross energy and  
                    phosphorus in the various diets fed to Oreochromis niloticus….........................121 
 
 
 
 
 
 
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LIST OF PLATES 
Plate 3.1 Interaction with fish farmers in the Prestea Huni-Valley District of  
                Western Region, Ghana…………………………………………………………........53 
Plate 3.2 Using hand-operated meat mincer to pellet prepared fish diet…………………....64 
 
Plate 3.3 Experimental hapas being mounted in a 0.2 hectare earthen pond at  
               ARDEC, Akosombo…...................................................................................................67 
Plate 3.4 Measuring of physico-chemical parameters in an experimental hapa in  
                the pond………………………………………………………………………………..73 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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APPENDICES 
I   Informed Consent Form……………………………………………………………………206 
II Fish Feeds and Feed Ingredients Survey…………………………………………………..208 
III Mean Living Weight (± SD) for each Treatment during Growth Trials………………..215 
IV Detailed Water Quality Parameter Range for the Various Dietary  
     Treatments and Open Pond Waters during Growth Trials……………………………...216 
 
 
 
  
 
 
 
 
 
 
 
 
 
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CHAPTER 1.0 INTRODUCTION 
1.1 Background Information 
The growing demand for fish protein in Ghana has motivated active development of 
aquaculture both at the commercial and peasant levels. The contribution of aquaculture 
production to the Ghanaian economy has grown over the past decade, with an annual 
average growth rate of 12.4% (FAO, 2006–2012).  Aquaculture is seen as an important 
foreign exchange earner, contributes to food security as well as providing much needed 
employment to many people in Ghana. The Ghana National Aquaculture Development 
Plan (GNADP) designed in 2012 and launched in 2014 was to increase the national fish 
stock from 27, 750 metric tonnes to 130, 000 metric tonnes in six years (GNADP, 2012).  
The GNADP is intended to generate about 220, 000 jobs within the same period. In 
general, fisheries are estimated to contribute 3 % of the total national gross domestic 
product (GDP) and 5 % of the agriculture GDP of Ghana (FAO, 2006–2012).  
 
Aquaculture is defined by FAO (1990) as “the farming of aquatic organisms including 
fish, molluscs, crustaceans and aquatic plants with some sort of intervention in the 
rearing process to enhance production, such as regular stocking, feeding and protection 
from predators”.  Farming of aquatic organisms may be individual or corporate 
ownership of the stock being cultivated. Increasing production capacity of aquaculture 
resources through intensification seems to be the way forward to meet the ever increasing 
demand for fish. This entails increasing primary, intermediate and terminal productivity 
capacities of our natural aquatic ecosystem and creation of productive artificial aquatic 
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ecosystems through proper planning, development and management (Sadiku and 
Jauncey, 1995). 
 
The first scientifically managed aquaculture facility in Ghana was put up by the 
University of Ghana at its Agricultural Research Station situated near Nungua, Accra in 
1959. By 1969, there were about 220 reservoirs of variable sizes in Northern Ghana 
(FAO, 2006–2012). In the 1980s, aquaculture received a major boost, especially in the 
Ashanti, Central, Eastern, Western and Greater Accra regions, this time from government 
as a way of meeting Ghana’s fish deficit (Mensah et al., 2006).  
 
Most fish farmers in Ghana use earthen ponds and rely on natural productivity while 
others supplement with agricultural by-products. Other systems of culture include the 
cages, pens and raceway systems, which are not commonly practised nationwide (Awity, 
2005). In terms of numbers, cages come after ponds. For instance, in 2012, a total of 2, 
278 cages whilst 4, 749 ponds were recorded in the country (FD, 2013). However, fish 
production during the year was higher in cages than in ponds. Production from ponds was 
1, 771.50 and that of cages was 24, 248.50 metric tonnes.    
 
The Nile tilapia (Oreochromis niloticus) is the major tilapia species cultured in Ghana. 
Most of the fish produced are either consumed directly by fish farmers or sold locally.  
Currently, there is a ban on tilapia import in Ghana (FAO, 2006–2012) and so there is a 
call for an increase in its production locally. However, there are constraints to the 
expansion of aquaculture in Ghana of which the main one being high cost of fish feed. 
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Feed is known to be a major determinant of successful growth and intensification of 
aquaculture production. It accounts for a major part (30-70 %) of the total operation cost 
of an average fish farm (El-Sayed, 2004; Rumsey, 1993). It is generally accepted that the 
highest recurring cost in aquaculture comes from feeds. Alone, feed accounts for about 
60-80 per cent of operational costs in intensive aquaculture (Rola and Hasan, 2007).  
With the increasing demand for food fish and the decline in capture fisheries production, 
aquaculture in Ghana is shifting from low density to high density culture that is 
traditional to semi-intensive or intensive culture. This will consequently lead to an 
unprecedented rise in the demand for feeds more than that of fertilizers (Kaushik, 1990). 
Aquaculture in Ghana started with the use of no feed, then the use of farm-made feeds to 
factory-made feeds. This demonstrates a real possibility of increasing production and 
reveals the potential importance of fish feeds in Ghana. Now aquaculture feeds have been 
considered a major subsector of the feed milling industry (Kaushik, 1990). From the 
economic point of view, feed cost appears to be one of the major constraints against the 
greater expansion of aquaculture. 
 
Fish meal is the major dietary protein source for fish feeds, commonly making up 
between 20˗60 % of fish diets (FAO, 2012a; Glencross et al., 2007; Watanabe, 2002). It 
has been estimated that in 2008, the aquaculture sector used 60.8˗71.0 % of world fish 
meal production (FAO, 2012a; Lim et al., 2008; Tacon and Metian, 2008). Dietary 
protein is the major and most expensive component of formulated fish feeds (Wilson, 
2002) and feed costs have tended to increase with the rising price of fish meal. For 
instance, the cost of fish feeds increased by 73 % from 2005 to 2008 (FAO, 2012a). 
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Therefore, in order to reduce feed costs and the use of fish meal in aquafeeds, more 
extensive use of alternative feed ingredients is needed (Burr et al., 2012; Hardy, 2010; 
Lim et al., 2008; Glencross et al., 2007). 
 
Although plant protein such as soybean meal has been used in fish feeds as a replacement 
for animal protein, trash fish (fish meal of marine origin) is still the main dietary protein 
source comprising 20˗60% of the feed (Da et al., 2011; Phumee et al., 2009; Hung and 
Huy, 2007). However, using fish meal is not a sustainable long-term feeding strategy 
(FAO, 2010; Naylor et al., 2009), because it will lead to the decline or extinction of some 
trash fish species (Edwards et al., 2004). As the aquaculture industry is projected to 
continue expanding, fish meal must be used more strategically as the required aqua feed 
production volumes increase (Güroy et al., 2012). This poses a major challenge for 
thousands of small-scale fish farmers, as the feed is a major component of the total 
production costs and many fish feed producers still rely heavily on trash fish and fish 
meal (Tacon and Metian, 2008). In 1993, Rumsey documented that cost effective 
practical aquaculture feeds can be produced without the use of fish meal with no apparent 
loss in fish growth in some species such as tilapia. Despite the fact that most plant 
ingredients are readily available at a lower cost than fish meal, their use within fish feeds 
is usually restricted by relatively low protein content, unbalanced essential amino acid 
profile, high levels of fibre and starch and the presence of one or more anti-nutritional 
factors (Agbo et al., 2011; NRC, 1993).  
 
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Increased use of cheap, locally available feed resources and more sustainable protein 
sources is considered a high priority in fish feed industry that could provide a way to 
reduce the total production costs (Hardy, 2010; Edwards and Allan, 2004). Other studies 
have also shown the use of different types of feedstuffs in traditional aquaculture, ranging 
from kitchen wastes and foliage in homestead-type fish farming to fishery and agro-
industrial by-products like oil cakes, wheat and rice bran, mill wastes, brewery waste, 
bean residues, silkworm pupae, poultry wastes, slaughterhouse wastes (blood and 
entrails), trash fish and fish offal (Pillay and Kutty, 2005). Cocoa pod husk and 
groundnut peel have also been used (Ofori, 2001).  
 
The most important characteristics of feedstuffs are the bioavailability of nutrients; 
hence, reliable data on different ingredients for each species need to be well considered 
as a necessary prerequisite (Fagbenro et al., 2003; Jauncey, 1993).  Digestibility of 
nutrients in fish diets needs to be studied because it is the digested feed which is absorbed 
and made available for cellular metabolism. The resultant of which are tissue synthesis 
and repair of worn-out tissues and various energy utilization channels (NRC, 1993; 
Yudkin, 1985). Borghesi et al. (2007) reported that knowing nutrient digestibility of feed 
ingredients elicit interchangeability of feed ingredients without reducing animal 
performance. De Silva and Anderson (1995) also observed that it is essential to have 
knowledge of the digestibility of the main ingredients as well as of the whole diet in feed 
formulation and manufacture. In combination, chemical analysis and apparent 
digestibility coefficient (ADC) results allow us to precisely estimate not only the 
contribution of a particular protein source to a complete fish feed but also how much feed 
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wastes and undigested nutrients (faeces) will potentially accumulate in fish pond (Jimoh 
et al., 2010; Koprucu and Ozdemer, 2005).  
 
Local or sub-regional agricultural by-products could provide nutritionally sound and cost-
effective feeds to support increased fish production in Ghana (Agbo, 2008). In order to 
increase and sustain aquaculture production in Ghana, there is the need to encourage use 
of the abundant locally available ingredients to develop low cost feeds and discourage 
import of very expensive formulated or pelletised feed from abroad (Agbo, 2008). Thus, 
production of fish diets using locally available feed ingredients for small-scale fish 
farming in Ghana is the way forward to increase the profitability of the industry and 
make the production more sustainable. In Ghana, there are a variety of agro-based 
industrial wastes, such as oil palm waste, pineapple waste, cassava waste, pawpaw waste, 
yam waste, and coconut waste. Efforts have been made to make use of these organic 
wastes in formulating feeds for animals, including fish. In addition to selecting the proper 
feeds or ingredients to develop cost effective feeds that will maximize growth, 
appropriate feed management and feeding practices are critical to obtaining efficient 
aquaculture production and minimizing pollution of the aquatic environment (NRC, 
2011).  
 
It is against this background that this study was designed to find answers to the following 
research questions: 
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 What types of feed ingredients and commercial fish diets are being used by small-
scale pond fish farmers in five major pond fish farming regions (Ashanti, Brong 
Ahafo, Central, Volta and Western) of Ghana? 
 What are the chemical constituents of the commonly used feed ingredients and 
commercial fish diets by the fish farmers? 
 What are the biological utilization levels of the commonly used commercial fish 
diets and farm-made (formulated) diets from the commonly used feed ingredients 
when fed to O. niloticus? 
 What is the state of health of O. niloticus when fed separately with the farm-made 
diets and the commonly used commercial ones? 
 Does feeding O. niloticus with the farm-made and commercial diets negatively 
impact on the physiological well-being (condition factor) of the fish? 
 Do the farm-made diets and commonly used commercial fish diets negatively 
impact pond/hapa water quality? 
 Does the water quality in the pond/hapa negatively impact on the condition factor 
of the cultuered fish? 
 Is the farm-made diets relatively cost-effective compared with the commonly used 
commercial ones? 
 
1.2 Aim of the Study  
This study was to generate information on the feed ingredients and commercial fish diets 
currently used by small-scale pond fish farmers in five major pond fish farming regions 
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in Ghana and to evaluate the commonly used commercial fish diets and farm-made diets 
produced with selected commonly used ingredients for O. niloticus. 
 
1.3 Objectives of the Study 
The specific objectives were to: 
1. Conduct a survey of feed ingredients and commercial fish diets small-scale pond 
fish farmers are currently using for fish production in five main pond fish farming 
Regions of Ghana;   
2. Determine the proximate compositions of commonly used feed ingredients and 
commercial fish diets by small-scale pond fish farmers in five main pond fish 
farming Regions of Ghana; 
3. Evaluate two most commonly used commercial diets and two farm-made diets 
formulated and prepared using six selected commonly used feed ingredients on 
growth and feed utilization of O. niloticus; 
4. Evaluate the digestibility of the commercial fish diets and the compounded ones 
in O.  niloticus;  
5. Assess the state of health and physiological well-being (condition factor) of O. 
niloticus when fed separately with the farm-made diets and that of commercial 
ones; 
6. Assess the effect of the farm-made diets and that of the commercial ones on water 
quality;  
7. Assess the effect of water quality in the hapas on the growth of the fish and 
8. Evaluate the cost effectiveness of the farm-made and commercial diets. 
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1.4 Justification of the Study 
Pond fish farming is on the increase in all the ten (10) Regions of the country (FD, 2013). 
Most of these farmers are small-scale producers who cannot afford the ever escalating 
cost of commercial fish diets. This could discourage most of them from being in the fish 
farm business which will negate national efforts on food security. Furthermore, there is a 
paucity of information on the nutrient contents of commercial fish feeds in Ghana as well 
as no reliable published information on chemical composition of these products (Personal 
Observation). Although there are guidelines for the establishment of a new fish feed 
industry (GNADP, 2012) these are yet to be enforced.  Hence, there is a great possibility 
that fish farmers may be deceived by the commercial feed manufacturers due to the 
quality assurance gap. Therefore, there is an urgent need to assess the actual chemical 
composition and nutritive value of commercial fish feeds and ingredients used by fish 
farmers in the country.    
 
Small-scale fish farmers may use ingredients based on location, affordability and 
seasonality. Plant feedstuffs are known to contain anti-nutritional factors (ANFs). ANFs 
limit the use of plant feedstuffs at high dietary inclusion levels in compounded fish feeds 
(Tacon, 1993). This study will provide appropriate information to small-scale fish 
farmers on the availability, proximate composition and the optimal inclusion levels of 
used ingredients in farm-made fish diet productions so that the farmers could develop 
suitable farm made fish feeds. Hence, small-scale fish farmers will be knowledgeable in 
the appropriate feed ingredients to utilize in their formulations as well as including each 
of them at their optimal levels. 
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 Currently, most commercial fish diets in Ghana are imported from Brazil and United 
States of America (USA) and they are prohibitively expensive for small-scale fish 
farmers to buy. Although some of these farmers could afford the cost of these diets, but 
with much difficulty. Consequently, most of the farmers have resorted to feeding their 
cultured fish with food scraps and food wastes from their farming activities. This practice 
makes the cultured fish take a significantly longer time period (10-12 months) to reach 
market size (Ashanti, Brong-Ahafo and Central Regional Small-Scale Fish Farmers 
Associations; Personal Communication). Farmers who compound their own feeds 
produced unbalanced diets as their productions do not follow an appropriate feed 
formulation protocol so as to meet the nutritional requirements of the target fish (Personal 
Observation). 
 
Imported commercial fish feeds continue to flood the local market due to the 
intensification of O. niloticus and expansion of the aquaculture industry in recent years. 
This is particularly in the Eastern and some parts of Volta Regions where cage fish 
farming is widespread due to the presence of the Volta River. Some of these commercial 
feeds may be of poor quality, and may not meet the nutritional requirements of the target 
fish. Currently, about sixteen (16) of these feeds have been recorded in the Eastern 
Region alone (Personal observation). Unlike quality commercial poultry feeds, that are 
readily available in Ghana, there is an acute paucity of nutritionally sound, cost effective 
feeds for finfish in general, and for O. niloticus in particular.  
 
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It is therefore necessary that data is gathered on the commercial fish feeds and feedstuffs 
currently utilized by small-scale pond fish farmers in Ghana so as to evaluate them for O. 
niloticus as it is the main fish cultured in the country. Ultimately, it is anticipated that 
value addition to the used feed ingredients in the five Regions will be a major 
contribution towards production of quality fish feed, cutting back fish feed cost and 
increasing the returns from fish farming in the country. The use of appropriate, cheap and 
locally available feed ingredients in farm-made fish feed production is necessary to 
increase fish farming yield, improve food security, reduce poverty among rural folks and 
create employment.  
 
 
 
 
 
 
 
 
 
 
 
 
 
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CHAPTER 2.0 LITERATURE REVIEW 
2.1 Fish Consumption Patterns in the World 
Global food fish supply has grown steadily in the last five decades, at an average annual 
rate of 3.2 percent, outpacing world population growth (1.6 %). Therefore, average per 
capita availability has risen. World per capita apparent fish consumption increased from 
an average of 9.9 kg (live weight equivalent) in the 1960s to 17.0 kg in the 2000s and 
18.9 kg in 2010, with preliminary estimates for 2012 pointing towards further growth to 
19.2 kg (FAO, 2014). However,  there are distinct regional differences; the lowest 
consumption is in Africa (9.1 kg/capita), followed by 9.9 kg for Latin America and the 
Caribbean, 20.7 kg for Asia, 22.0 kg for Europe, 24.1 kg for North America, and 24.6 kg 
for Oceania (FAO, 2012a, 2012b). Although consumption has grown steadily in 
developing regions (5.2 kg in 1961 to 17.0 kg in 2009) and in low-income food-deficit 
countries (LIFDC; 4.9 kg in 1961 to 10.1 kg in 2009), levels are still considerably less 
than in more developed regions. These aggregate figures cover a very wide variation in 
consumption, influenced by location, tradition, household customs, fish access, trade 
connections, market power, and emerging consumption drivers such as urbanization, 
income distribution changes, and retail development (FAO/SFLP, 2008).  
 
In Africa, fish provides about 22 % of the protein intake in sub-Saharan Africa (SSA) 
(FAO, 2012b). This can, however, exceed 50 % in the poorest countries, especially where 
other sources of animal protein are scarce or expensive (WorldFish Center, 2005). Per 
capita fish consumption has remained static or decreased in some countries in SSA (e.g. 
the Congo, South Africa, Gabon, Malawi and Liberia), whilst the most substantial 
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increases in annual per capita fish consumption have occurred in North Africa (from 2.8 
kg in 1961 to 10.6 kg in 2009) (FAO, 2012b). Of the 126 million tonnes available for 
human consumption in 2009, fish consumption was lowest in Africa (9.1 million tonnes 
with 9.1 kg per capita). This has been attributed to levelling off in capture fish production 
and increasing population growth (World Bank, 2004). Based on 1997 levels of 
production, aquaculture would have to increase by 267 % by 2020 to maintain the current 
fish consumption level in Africa (Delgado et al., 2003).  
 
In Ghana, fish is the preferred source of animal protein and it is consumed by the 
majority of the people. Ghana is among the highest fish consuming countries in the 
world, with an average per capita consumption of 25 kg. With a population of 
approximately 24 million fish demand for 2012 was estimated at 968, 000 metric tonnes, 
whilst fish production for the same year stood at 486, 000 metric tonnes (MoFA, 2013). 
About 175, 000 metric tonnes of fish were imported at an estimated cost of $ 157 million 
to make up for the shortfall. The demand for fish is higher than what total domestic fish 
catch can supply and the gap is widening year after year. Fish provides approximately 60 
% of the animal protein consumed in Ghana (GFAR, 2011). About 75 % of the total 
domestic fish (captured and farmed) is consumed locally. The preferred fish species in 
Ghana are the sea bream, red snapper and croaker but these are expensive and 
unaffordable by the majority of the population. Thus, the affordable types-mackerel, 
horse mackerel, chub mackerel, sardines and tuna are mostly consumed (GFAR, 2011).  
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2.2 Contribution of Fish to Human Health and Food Security 
Consumption of fish can play a key role in access to proteins, minerals, and essential 
fatty acids, and can have a significant impact for maternal and early child health 
(Kawarazuka and Béné, 2011; Thilsted et al., 1997).  There is evidence of beneficial 
effects of fish consumption (FAO/WHO, 2011) in relation to coronary heart disease 
(Mozaffarian and Rimm, 2006) stroke, age-related muscular degeneration and mental 
health (Peet and Stokes, 2005). Also, increasing consumption of fish has been found to 
enhance learning in children, protects vision and eye health, and offers protection from 
cardiovascular disease and some cancers (FAO, 2012b). The role of small indigenous fish 
species, which are often given less prominence in fishery or aquaculture development, 
can be very critical for poorer households in reducing protein, vitamin and mineral 
(especially calcium and iodine) deficiencies (Roos et al., 2007).  
 
Food fish currently represents the major source of animal protein (contributing more than 
25 percent of the total animal protein supply) for about 1 250 million people within 39 
countries worldwide, including 19 sub-Saharan countries (FAO, 2009). Fish contributes 
more than 50 percent of protein intake for about 400 million people from the poorest 
African and South Asian countries. The quality of fish protein compares very well with 
that of meat and relatively fish digestion is easier than that of meat (Steiner-Asiedu et al., 
1993). The ease of digestion makes it an excellent protein source in complementary foods 
for young child feeding, especially in less developed countries. Fish provides not only 
high-value protein, but also a wide range of essential micronutrients, including various 
vitamins (A, B, D and E), and minerals (including calcium, iodine, zinc, iron and 
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selenium) and polyunsaturated omega-3 fatty acids (mainly docosahexaenoic acid and 
eicosapentaenoic acid) (FAO, 2012b; Roos et al, 2007). Generally, fish is usually low in 
saturated fats and cholesterol. The fats and fatty acids in fish, particularly the long chain 
n-3 fatty acids (n-3 polyunsaturated fatty acids (PUFAs)), are highly beneficial and 
difficult to obtain from other food sources (Kawarazuka and Béné, 2011). Of particular 
importance are eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-
3, DHA).  
 
With a primary policy focus on access to food calories, fish or aquatic foods have been 
relatively under-recognized in their contribution to global food supply and food security 
(FAO, 2012b). However, in 2009, fish accounted for 16.6% of the world’s intake of 
animal protein and 6.5% of all protein consumed, providing around 4.3 billion people 
with about 15% of their animal protein. With growing recognition of the need to define 
global targets of food sufficiency and security by nutritional quality (FAO, 2012b; Shetty, 
2009), particularly in maternity and early life stages, the role of fish is becoming much 
more clearly appreciated. 
 
Interactions between fishing and food security are also critical in many parts of the world, 
where small-scale and often seasonal fishing activity provides both income and 
household food supply, and there is common concern that over-zealous regulation and 
removal of fishing capacity may cause more negative social and nutritional impact than 
the resource efficiency gains being sought (Béné et al., 2010). However, though 
aquaculture might supplement or compensate for capture fisheries, Beveridge et al. 
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(2010) note its constraints of meeting lowest income social objectives, as small- and 
medium-scale commercial producers and wealthier market/retail consumers are more 
likely to benefit. However, through market displacement, by producing smaller 
indigenous species in polycultures, and/or by providing occasional employment for cash 
or food, additional benefits may be provided for poorer groups. There are also important 
consequences of trading fish for other food items, either locally or at the market economy 
level (Kurien, 2004). In favourable conditions this can create advantages for all parties, 
widening and expanding nutritional options for catchers/producers of fish while 
improving access to key foodstuffs. This is particularly valuable for peri-urban supplies 
and urban markets, though there may be issues of reduced local market access where 
higher urban prices drive out purchasing options. The development of infrastructure–road 
access, ice production, and market facilities may also accelerate the shift to urban 
markets. However, there are also specific challenges with meeting needs of poor urban 
dwellers (Ruel et al., 2008), particularly where urbanization is rapid and is not 
accompanied by strong employment opportunities. It is clear that expansion of fish 
supplies will be essential to meet future food needs.  
 
2.3.1 Global Production of Aquaculture 
Global food fish aquaculture production expanded at an average annual rate of 6.2 
percent in the period 2000–2012, more slowly than in the periods 1980–1990 (10.8 
percent) and 1990–2000 (9.5 percent) (FAO, 2014). Between 1980 and 2012, world 
aquaculture production volume increased at an average rate of 8.6 percent per year. 
World food fish aquaculture production more than doubled from 32.4 million tonnes in 
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2000 to 66.6 million tonnes in 2012, with an estimated total value of US$137.7 billion 
(FAO, 2014). Of the 66.6 million tonnes of farmed food fish produced in 2012, two-
thirds (44.2 million tonnes) were finfish species grown from inland aquaculture (38.6 
million tonnes) and mariculture (5.6 million tonnes). When farmed aquatic algae (mostly 
seaweeds) are included, world aquaculture production in 2012 was 90.4 million tonnes, 
worth US$144.4 billion.  FAO estimates that world food fish aquaculture production rose 
by 5.8 percent to 70.5 million tonnes in 2013, with production of farmed aquatic plants 
(including mostly seaweeds) being estimated at 26.1 million tonnes (FAO, 2014). By 
continent, annual aquaculture production growth was fastest in Africa (11.7 %) and Latin 
America and the Caribbean (10 %) in the first twelve years of the new millennium (FAO, 
2014). When China is excluded, the expansion in farmed food fish production in the rest 
of Asia recorded an annual growth rate of 8.2 % from 2000 to 2012, which is 
significantly higher than in the periods 1980–1990 (6.8 %) and 1990–2000 (4.8 %). The 
annual growth rate in China, the single largest aquaculture producer, fell to an average of 
5.5 % in the period 2000–2012, less than half that of 1980–1990 (17.3 %) and 1990–2000 
(12.7 %). Europe and Oceania had the lowest average annual growth rates in the period 
2000–2012 at 2.9 and 3.5 %, respectively. In sharp contrast to other regions, production 
in North America started to shrink gradually from 2005 and, by 2012, was lower than in 
2000, owing to the production fall in the United States of America (FAO, 2014). 
 
Worldwide, 15 countries produced 92.7 percent of all farmed food fish in 2012, with Asia 
accounting for about 88 % of total production by volume. Cut to just over half a million 
tonnes by the 2011 tsunami, Japan’s aquaculture production recovered slightly to more 
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than 0.6 million tonnes in 2012 (FAO, 2014). Production peaked at more than 0.6 million 
tonnes in both the United States of America and the Republic of Korea in 2004 and 2007, 
respectively. In 2012, their respective production levels were slightly more than 0.4 
million tonnes and just less than 0.5 million tonnes. Farmed food fish production has 
been rising steadily among the other leading producers, except in Chile, where disease 
outbreaks in marine cage culture of Atlantic salmon hit production in 2009–2010 before 
recovery and further expansion in production in 2011–12 (FAO, 2014). 
 
World aquaculture production can be categorized into inland aquaculture and 
mariculture. Inland aquaculture generally use freshwater, but some production operations 
use saline water in inland areas (such as in Egypt) and inland saline-alkali water (such as 
in China). Mariculture includes production operations in the sea and intertidal zones as 
well as those operated with land-based (onshore) production facilities and structures 
(2014). 
 
More than 600 aquatic species are raised in captivity worldwide for production in a 
variety of farming systems and facilities of varying input intensities and technological 
sophistication, using freshwater, brackish water and marine water (FAO, 2014). 
However, the stage of development and the distribution of aquaculture production remain 
imbalanced in all regions. A few developing countries in Asia and the Pacific, SSA and 
South America have made considerable progress in aquaculture development in recent 
years and they are becoming significant or major producers in their respective regions 
(FAO, 2014). However, the disparity remains huge across the continents and georegions, 
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as well as among countries of comparable natural conditions in the same region, with 
aquaculture in many of the least developed countries yet to make a significant 
contribution to national food and nutrition security. 
 
World aquaculture production is vulnerable to adverse impacts of natural, socioeconomic, 
environmental and technological conditions (FAO, 2012a, WWF, 2012). In 2010, 
aquaculture in China suffered production losses of 1.7 million tonnes (worth US$3.3 
billion) caused by diseases (295 000 tonnes), natural disasters (1.2 million tonnes), 
pollution (123 000 tonnes) etc. Disease outbreaks virtually wiped out marine shrimp 
farming production in Mozambique in 2011 (WWF, 2012). 
 
Total aquaculture production in Africa in 2012 was estimated to be 1 485 367 mt which is 
about 2.23 % of global production by volume. North Africa contributed about 1 030 675 
mt whilst SSA contributed about 454 691 mt accounting for 69.39 and 30.61 % 
respectively of African production (FAO, 2014). Aquaculture production in SSA is 
dominated by Nigeria contributing about 15.57 % with the other top five producers 
(Uganda, Kenya, Zambia, Ghana and Madagascar) together contributing about 10.43 % 
of the total production in 2010. Between 2000 and 2010, overall aquaculture production 
in SSA increased by 84.52 % from 55 690 mt to 359 790 mt (FAO, 2012a). More than 70 
% of total aquaculture production in SSA comes from commercial farms, produced by 
less than 20 % of farmers, whilst the remaining less than 30 % is produced by small-scale 
farmers that represent over 80 % of all farmers (Hecht, 2007). The systems used by the 
commercial sector range from semi-intensive to intensive pond, cage and tank culture of 
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catfish (Clarias spp.) and tilapia (Oreochromis spp.) and high-valued products such as 
shrimp (Madagascar and Mozambique) and abalone (South Africa) while noncommercial 
subsistence aquaculture primarily consists of small-scale pond culture of tilapia, catfish 
and common carp, Cyprinus carpio (Hecht, 2007). Machena and Moehl (2001) reported 
that the major aquaculture products in Africa are mainly fresh- and brackish-water 
finfish. 
 
The share of freshwater aquaculture production in Africa increased from 21.8 percent in 
the 1990s to 39.5 percent in 2010 as a result of rapid development in freshwater fish 
farming in Nigeria, Uganda, Zambia, Ghana and Kenya (FAO, 2012a). African 
aquaculture production is mainly finfishes (99.3 percent by volume), with only a small 
fraction from marine shrimps (0.5 percent) and marine molluscs (0.2 percent). In spite of 
some limited successes, the potential for bivalve production in marine waters remains 
almost completely unexplored. 
 
In Ghana, aquaculture became important in the 1980’s when the Government of Ghana 
(GoG) recognized fish farming as an assured way of meeting the deficit in Ghana's 
protein requirements (GFAR, 2011). Due to massive GoG support, fish farming became 
established in many parts of the country. However, the growth of the sector was slow due 
in part to the subsistence nature of fish farming, inefficient and inappropriate production 
practices, and dependency on government support. In addition, the sector faced many 
challenges including lacking inputs such as fingerlings and fish feed produced 
commercially to support the growth of the industry (GFAR, 2011).  
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Commercial fish farming in Ghana is a recent development that has been adopted in the 
past few years. Presently, there are about seven main commercial aquaculture farms 
operating in Ghana and over 200 medium/small-scale fish farms. In the last five years 
aquaculture production has increased by 80 percent from 2005 to 2010 as a result of 
proliferation of commercial fish farming particularly the cage farming on the Lake Volta 
(GFAR, 2011).  
 
Tilapia constitutes about 80 % of aquaculture production while catfish and others account 
for the remaining 20 %. While there is no major shrimp/prawn farming in Ghana yet, 
research shows that there is a great potential for commercial farming of local shrimp 
species (GFAR, 2011). The majority of the aquaculture operators grows or culture fish in 
earthen ponds either as a monoculture of tilapia or poly-culture of tilapia with catfish.  
Cage fish farms contribute over 80 percent of total fish yield in aquaculture production. 
The commercial operators do not produce their own fish feed but buy high quality 
pelletized balanced feed from animal feed companies (GFAR, 2011).  
 
Most medium/small-scale fish farmers do not produce their own fingerlings, instead they 
buy from the large scale farmers; others collect old stocks from other fish ponds or from 
rivers and streams. Tilapia fingerlings used on most medium/small-scale fish farms are 
mostly of poor quality (GFAR, 2011). The small/medium-scale operators produce various 
species of tilapia and catfish. Most small/medium-scale fish farmers rely on the natural 
productivity of the ponds to achieve their production. Others use agricultural by products, 
or poor quality feedstuffs in unbalanced proportions to feed tilapia.  
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2.4 Aquaculture Growth and Fish Feeding 
In 2012, global aquaculture production totalled 90.4 million tonnes, made up of 66.6 
million tonnes of food fish (i.e. finfishes, crustaceans, molluscs, amphibians, freshwater 
turtles, sea cucumbers, sea urchins, sea squirts and edible jellyfish) and 23.8 million 
tonnes of aquatic algae (mostly seaweeds) (FAO, 2014). Farmed food fish contributed 
42.2 % of the total 158 million tonnes of fish produced by capture fisheries (including for 
non-food uses) and aquaculture in 2012. This compares with just 13.4 % in 1990 and 25.7 
% in 2000 (FAO, 2014). Asia as a whole has been producing more farmed fish than wild 
catch since 2008, and its aquaculture share in total production reached 54 % in 2012, with 
Europe at 18 % and other continents at less than 15 %. FAO estimates in 2012 indicated 
that about 46.1 million tonnes (69.2 percent of total global aquaculture production 
including aquatic plants) of fish and crustaceans were feed-dependent, either as farm-
made aquafeeds or as industrially manufactured compound aquafeeds (FAO, 2014). 
Continuing its established trend, the share of fed species in total farmed food fish 
production increased further from 66.5 % in 2010 to 69.2 % in 2012, reflecting a 
relatively stronger growth in the farming of fed species (FAO, 2014). 
 
While more than 200 species of fish and crustaceans are currently believed to be fed on 
externally supplied feeds, just 8 species or species groups account for 62.2 percent of the 
total feed used. These are: grass carp, common carp, Nile tilapia, Indian major carps 
(catla and rohu), whiteleg shrimp, crucian carp, Atlantic salmon, and pangasiid catfishes. 
More than 67.7 percent of farmed fed fish production is contributed by freshwater fishes, 
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including carps and other cyprinids, tilapias, catfishes and miscellaneous freshwater 
fishes (FAO, 2012a). 
 
2.5 Production and Use of Fish Feed 
Compound aquafeeds are used for the production of both lower-value (in marketing 
terms) food fish species, such as non-filter-feeding carps, tilapias, catfishes and milkfish, 
as well as higher-value species, such as marine finfishes, salmonids, marine shrimps, 
freshwater eels, snakeheads and crustaceans (FAO, 2012a). Globally, 708 million tonnes 
of industrial compound animal feeds were produced in 2008, of which 29.2 million 
tonnes were aquafeeds (4.1 percent of all animal feeds). As animal production has 
increased, so has global industrial compound animal feed production – almost fourfold 
from 7.6 million tonnes in 1995 to 29.2 million tonnes in 2008, at an average rate of 11 
percent per year (FAO, 2012a). Production is expected to grow to 51.0 million tonnes by 
2015 and to 71.0 million tonnes by 2020. 
 
While there is no comprehensive information available on the global production of farm-
made aquafeeds (De Silva and Hasan, 2007), the estimate is that it was between 18.7 
million and 30.7 million tonnes in 2006. More than 97 percent of carp feeds used by 
Indian farmers are farm-made aquafeeds (7.5 million tonnes in 2006/07), and they are the 
mainstay of feed inputs for low-value freshwater fishes in many other Asian and sub-
Saharan countries. 
  
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2.6 Feed Ingredient Production and Availability 
Feed ingredients used for the production of aquafeeds are broadly categorized into three 
types depending upon their origin: animal nutrient sources (including both aquatic and 
terrestrial animals); plant nutrient sources; and microbial nutrient sources (Tacon et al., 
2012).    
 
2.6.1 Animal Nutrient Sources 
The major aquatic animal protein meals and lipids used in aquafeeds include: 
fish/shellfish meals and oils; fish/shellfish by-product meals and oils; and zooplankton 
meals and oils (FAO, 2012a). The major terrestrial animal protein meals and lipids 
commonly used in aquafeeds are: (i) meat by-product meals and fats; (ii) poultry by-
product meal, hydrolysed feather meal and poultry oil; and (iii) blood meals (Tacon et al., 
2011). In recent years, increasing volumes of fishmeal and fish oil have originated from 
fisheries by-products (capture fisheries and aquaculture). An estimated 6 million tonnes 
of trimmings and rejects from food fish are currently used for fishmeal and fish-oil 
production (Tacon et al., 2011).  Although some marine zooplanktons have potential for 
use as feed ingredients for aquaculture, commercial operations only exist for Antarctic 
krill (Euphausia superba), with total landings of 118 124 tonnes in 2007 (Tacon et al., 
2011). Although krill meal and krill oil are available, information concerning their total 
global production and market availability is currently unavailable.  
 
Processed animal protein ingredients (often referred to as land animal products) such as 
blood meal, feather meal and poultry by-product meal are comparable with many other 
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protein sources used in fish feeds on a cost-per unit protein basis (NRC, 2011). No effects 
on growth performance and feed utilization were observed when fish meal protein in 
finfish diets was replaced with 60˗80% of poultry by-products (PBM) or with 30˗40% 
hydrolysed feather meal (FeM) (Yu, 2008). A number of published reports are available 
regarding the suitability of different animal protein feeds as alternatives to fish meal in 
fish feeds (Rossi Jr and Davis, 2012; Hernández et al., 2010; El-Haroun et al., 2009; 
Rawles et al., 2009; Hu et al., 2008; Saoud et al., 2008; Wang et al., 2008; El-Sayed, 
1998). 
 
2.6.2 Plant Nutrient Sources 
The major plant dietary nutrient sources used in aquafeeds include: cereals, including by-
product meals and oils; oilseed meals and oils; and pulses and protein concentrate meals 
(Tacon et al., 2011). Total global cereal production was 2 489 million tonnes in 2009, 
with maize totalling 817.1 million tonnes (32.8 percent of the total), followed by wheat, 
rice paddy, and barley. In 2009, oilseed production was 415 million tonnes, with soybean 
being the largest and fastest-growing oilseed crop and accounting for slightly more than 
50 percent (210.9 million tonnes) of this total. Among the pulses, protein concentrate 
meals from peas and lupins are commercially available for use within compounded 
animal feeds, including aquaculture feeds.  
 
Using plant-based proteins in aquaculture feeds requires that the ingredients possess 
certain nutritional characteristics, such as low levels of fibre, starch and anti-nutritional 
compounds. They must also have a relatively high protein content, favourable amino acid 
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profile, high nutrient digestibility and reasonable palatability (NRC, 2011; Lim et al., 
2008). A number of previous studies discuss the suitability of plant protein feeds and/or 
local agricultural by-products as an alternative protein source in fish feeds (Burr et al., 
2012; Bonaldo et al., 2011; Brinker and Reiter, 2011; Cabral et al., 2011; Nyina-
Wamwiza et al., 2010; Pratoomyot et al., 2010; Garduño-Lugo and Olvera-Novoa, 2008; 
Olsen et al., 2007). 
 
Duckweeds grown on water with 10-30 mg NH3-N/litre have high protein content 
(around 40%) of high biological value (Hillman and Cully, 1978). Fresh duckweed is 
highly suited to intensive fish farming systems with relatively rapid water exchange for 
waste removal (Gaigher et al., 1984) and duckweed is converted efficiently to live weight 
by certain fish including carp and tilapia (Hasan and Edwards, 1992; Robinette et al 
1980; Hepher and Pruginin, 1979; Van Dyke and Sutton, 1977). A duckweed lagoon with 
a standing crop of duckweed is harvested and placed fresh into a second lagoon 
containing a mixed size tilapia culture. The pond is harvested twice weekly and the fish 
sorted into various groups for return to the lagoon or sale. Under these circumstances the 
average yield of fish per hectare of lagoon is estimated at around 10 tonnes annually 
using only duckweed as the supplement to the naturally available fish feed (Skillicorn et 
al., 1993). 
 
2.6.3 Microbial Ingredient Sources 
Microbial-derived feed ingredient sources for aquafeed include algae, yeasts, fungi, 
bacteria and/or mixed bacterial/microbial single-cell protein sources (Tacon et al., 2011). 
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The only such sources available in commercial quantities globally are yeast-derived 
products, including brewer’s yeast and extracted fermented yeast products, but with 
limited information concerning their total global production and availability (FAO, 
2012a). Given the relatively low cost of some of these single-cell proteins, they are 
probably most relevant as a major protein ingredient in fish feed or may at least partially 
replace fishmeal in feeds for some fish species (FAO, 2012a). 
  
Various species of macroalgae and microalgae have been incorporated into fish feed 
formulations to assess their nutritional value, and many have been shown to be beneficial: 
Chlorella or Scenedesmus fed to Tilapia (Tartiel et al., 2008); Chlorella fed to Korean 
rockfish (Bai et al., 2001); Undaria or Ascophyllum fed to Sea Bream (Yone et al., 
1986); Ascophyllum, Porphyra, Spirulina, or Ulva fed to Sea Bream (Mustafa and 
Nakagawa, 1995); Gracilaria or Ulva fed to European Sea Bass (Valente et al., 2006); 
Ulva fed to Striped Mullet (Wassef et al., 2001); Ulva or Pterocladia fed to Gilthead Sea 
Bream (Wassef et al., 2005); Porphyra or a Nannochloropsis-Isochrysis combination fed 
to Atlantic Cod (Walker et al., 2009, 2010). Unfortunately, it has rarely been possible to 
determine the particular nutritional factors responsible for these beneficial effects, either 
because no attempt was made to do so or poor design of the study. For example, in one of 
the few studies that has focused on the effects of substituting algal protein for gluten 
protein, the control and all the test diets contained casein plus added methionine and 
lysine, no analysis of the algal protein was provided, and the algal protein (a biofuel 
process by-product) contained very high levels of aluminium and iron (Hussein et al., 
2012). 
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2.7 Anti-nutrients in Feed Ingredients 
The use of plants or plant-derived feedstuffs such as legume seeds, different types of 
oilseed cake, leaf meal, leaf protein concentrates and root tuber meals as fish feed 
ingredients is limited by the presence of a wide variety of anti-nutritional substances 
(Francis et al., 2001) (Table 2.1). However, only a few are of major importance for fish 
feed formulation. The effects of these substances on fish can include reduced palatability, 
altered nutrient balance of the diet, disturbance of digestive processes and growth, 
decreased feed efficiency, pancreatic hypertrophy, hypoglycaemia, liver dysfunction, 
goiterogenesis and immune suppression (NRC, 2011; Krogdahl et al., 2010).  
 
It has been observed that common processing techniques, such as cooking, soaking, 
drying and wet heating, as well as adding feed supplements, can reduce the concentration 
of anti-nutritional factors in plant feeds and improve the feed intake (Rehman and Shah, 
2005; Francis et al., 2001; Alonso et al., 2000). By-products of animal origin may also 
contain anti-nutritional compounds, especially if the products are not properly preserved 
or processed (NRC, 2011). However, whilst some anti-nutritional factors are easy to 
eliminate by processing, others may be more difficult to eliminate. 
 
 
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Table 2.1 Anti-nutrient compounds and their biological effects on animals 
Compound  Biological effects                 References 
Fibres 
 
Interfere with digestion, absorption and utilization of macro- and micro-
nutrients. 
Van Der Kamp et al. (2004) 
 
Phytic acid Impairs mineral digestion and contains phosphorus in a form unavailable to 
monogastrics. 
 
Thompson (1993) 
Protease inhibitors Growth reduction, inhibition of proteolytic enzymes. Francis et al. (2001) 
 Enzyme inhibitors Reduce the digestion of protein, carbohydrates and lipids. Thompson (1993); Krogdah and Holm 
(1979) 
 Goitrogen  Growth reduction, thyroid hyperplasia, changes in T3 and T4 levels. 
 
Francis et al. (2001) 
Oestrogens Growth reduction, induction of vitellogenin secretion. Francis et al. (2001) 
 Lectins  Make the gut more permeable for increased influx of macromolecules and 
bacteria, stimulate insulin production and alter metabolism. Growth reduction. 
 
Grant (1991) 
Saponins  Interfere with lipid and protein digestion. Growth and feed efficiency reduction. 
 
Cuadrado et al. (1995) 
Glucosinolates  Reduce the uptake of iodine into the thyroid gland and may lead to goitre.  
 
Liener (1980) 
Cyanogens  Respiratory failure. Growth and feed efficiency reduction. 
 
Liener (1980) 
Phytoestrogens Interfere with endogenous oestrogen. Price and Fenwick (1985) 
 
Phytosterols  Interfere with cholesterol absorption and metabolism. Ostlund Jr et al. (2003) 
 
Quinolizidine 
alkaloids 
Lupine alkaloids, may cause nervous symptoms and intestinal disorders.  
 
Wink et al. (1998) 
Oligosaccharides  Alter the microbiota in the gut and increase osmotic pressure in the intestine. 
 
Cummings et al. (1986) 
Alkaloids Growth and reduced feed palatability, liver abnormalities. Francis et al. (2001) 
 
Anti-vitamins Reduced vitamin availability.  Melcion and Poel (1993) 
 
Toxic fatty acids Effect on reduction mortality. Liener (1980) 
 
Data source: Adapted from Hardy (2010); Krogdahl et al. (2010); Francis et al. (2001); Melcion and Poel (1993).
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2.8 Culturing of Tilapia  
 “Tilapia” is a generic term which is used to designate a group of commercially important 
food fish belonging to the family Cichlidae. Tilapia have been raised as food for human 
consumption for a long time; illustrations from Egyptian tombs suggest that the Nile 
tilapia, Oreochromis niloticus, was cultured more than 3000 years ago (Maar et al., 
1966). Tilapia is referred to as “Saint Peter’s fish” in reference to biblical passages about 
the fish fed to the multitudes (Popma and Masser, 1999). Although endemic to Africa 
their distribution has been extended by introduction to include much of the tropics and 
subtropics. More than 100 species have been identified (Balarin, 1979). Currently, tilapia 
culture is widely practised in many tropical and subtropical regions of the world. More 
than 22 tilapia species are being cultured worldwide. However, Nile tilapia (Oreochromis 
niloticus), Mozambique tilapia (O. mossambicus), blue tilapia (O. aureus), O. hornorum, 
O. galilaeus, Tilapia zillii and T. rendalli are the most commercially cultured tilapia 
species (Fitzsimmons, 2000). Tilapia species are used in commercial farming systems in 
almost 100 countries and are developed to be one of the most important fish for 
aquaculture in this century. 
 
2.9 Reproduction in Nile Tilapia 
Sexual maturity of Nile tilapia is reached at 10-30 cm total length (TL) and is related to 
the maximum size attained in a given population and condition, which in turn is 
determined by food availability and temperature (Trewavas, 1983; Pullin and Lowe-
McConnell, 1982). Reproduction occurs only when temperature exceeds 20 °C. The 
breeding cycle is latitude dependent and spawning becomes more seasonal at higher 
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latitudes. In many instances the breeding cycle is synchronized with the rainy season 
(Trewavas, 1983). The species is a nest building, batch spawning mouth brooder that can 
spawn every 30 days. The nest, like in many tilapiine fishes, is a circular depression in 
sandy areas of up to 1m in diameter and 0.5 m deep. The average nest diameter is twice 
the length of the male making it. Males are highly territorial and defend their nests 
(Trewavas, 1983). Batches of eggs are spawned into the nest, fertilized externally and 
then picked up by the female. The female incubates the eggs for 5-7 days when they 
hatch and the early fry remain in the mouth until after yolk sac absorption. Depending on 
size, females can carry up to 200 eggs. The eggs are large and ovoid (pear shaped) and at 
hatching the fish are around 4 mm in length (Trewavas, 1983). 
 
2.10 Natural Food and Feeding Habits of Nile Tilapia 
Early juveniles and young fish are omnivorous, feeding mainly on zooplankton and 
zoobenthos but also ingest detritus and feed on aufwuchs and phytoplankton (Beveridge, 
2000; Moriarty and Moriarty, 1973; Moriarty et al., 1973). At about 6 cm TL the species 
becomes almost entirely herbivorous feeding mainly on phytoplankton, using the mucus 
trap mechanism and its pharyngeal teeth. The pH of the stomach varies with the degree of 
fullness and when full can be as low as 1.4, such that lysis of blue-green and green algae 
and diatoms is facilitated (Moriarty, 1973). Enzymatic digestion occurs in the intestine 
where pH increases progressively from 5.5 at the exit of the stomach to 8 near the anus. 
Nile tilapia exhibits a dual feeding pattern. Ingestion occurs during the day and digestion 
occurs mainly at night (Trewavas, 1983). The digestive tract of Nile tilapia is at least six 
times the total length of the fish, providing abundant surface area for digestion and 
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absorption of nutrients from its mainly plant-based food sources (Opuszynski and 
Shireman, 1995). 
 
2.11 Growth of Nile Tilapia 
A study on the growth of 10 populations of O. niloticus under natural conditions showed 
that the  von Bertalanffy growth function parameters range as follows: L∞ (cm) = 22.9 to 
57.2, K = 0.14 to 0.51 and to = -0.85 to 0.54 (Merona et al., 1988). The maximum 
recorded size is 64 cm TL (Lake Kyoga) and in Lake Turkana fish of up to 7 kg have 
been recorded (Trewavas, 1983). The range of von Bertalanffy growth function 
parameters for cultured Nile tilapia as modelled by Moreau and Pauly (1999) were: L∞ 
(cm) = 16.6 to 41.8, K = 0.637 to 4.566 and Ø’ = 2.93 to 3.43. The wide range of values 
reported for Nile tilapia under natural conditions reflects the phenotypic response to the 
prevailing environmental conditions of the species and under culture condition is 
determined by sex ratio, stocking density, culture systems, feeds, temperature and water 
quality (Abdel-Tawwab and El-Marakby, 2004).  
 
Several organizations have invested substantial resources in the genetic improvement of 
Nile tilapia. The Genetically Improved Farmed Tilapia (GIFT) strains developed by the 
WorldFish Center as well as other strains (GET EXCEL, GenoMar ASA and GenoMar 
Supreme Tilapia) have significantly better growth performance than “unaltered” strains 
(Asian Development Bank, 2005).  
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2.12 Use of Formulated Feeds for Nile Tilapia 
High quality formulated feeds are used to achieve high yields and large sized fish (600-
900 g) within a short period of time (Dey, 2001).  Under semi-intensive farming systems, 
most tilapia farmers in Asia fertilize their ponds and use formulated feeds. However, in 
intensive pond and tank culture systems or in cages, tilapia farmers mainly depend on 
commercial pelleted feeds. In terms of pond yields, Dey (2001) reported that overall, the 
average yield of pond farming in Taiwan, Province of China is very high (12 to 17 
tonnes/ha) while ponds in Bangladesh, China, the Philippines, Thailand and Vietnam 
produce around 1.7, 6.6, 3.0, 6.3 and 3.0 tonnes/ha, respectively.  
 
Tilapia feeds accounted for about 8.1 percent of global aquafeed production in 2003 
(Tacon et al., 2006). Commercial tilapia feeds are mainly dry sinking pellets and 
extruded floating pellets. Production estimates for farm-made tilapia feeds are not 
available as these are usually site specific and dependent on locally available feed 
ingredients (Tacon et al., 2006). In countries such as the Philippines, on-farm feeds are 
not very popular as tilapia farmers find it more convenient to purchase formulated feeds 
from feed companies.   
 
The main issue in formulating feed is to meet the protein and essential amino acids 
(EAAs) requirements of the species to facilitate tissue/muscle growth. Fishmeal is 
generally the preferred protein source because of the high quality of the protein and its 
EAA profile (Jauncey and Ross, 1982). However, fishmeal is generally expensive and is 
not always available. Nile tilapia can be fed with a high percentage of plant proteins 
(Mbahinzireki et al., 2001; Ofojekwu and Ejike, 1984). It is economically judicious to 
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replace fishmeal with alternative protein sources including animal by-products, oilseed 
meal and cakes, legumes and cereal by-products and aquatic plants (Agbo et al., 2011; 
Rumsey, 1993). Most of these ingredients are deficient in some EAA and hence require 
supplementation or be compensated with other feedstuffs. Although most of the oilseed 
cakes/by-products are generally deficient in lysine and methionine, blending of different 
oilseed cakes often provides balanced amino acid profile (Lim and Webster, 2006). 
However, they contain many anti-nutritional factors (such as gossypol, glucosinolates, 
saponins, trypsin inhibitors etc.) which limit their use in compound feeds or require 
removal/inactivation through specific processing (such as heating, cooking etc.) (NRC, 
1993). There are also several non-conventional protein sources that may be suitable for 
O. niloticus such as silkworm pupae, snails, earthworms, Spirulina, corn and wheat 
gluten, almond cake, sesame cake, brewery waste etc. 
 
2.13 Feeding Schedules (Rates and Frequencies) for Cultured Tilapia  
Feeding rate (allowance) in practical feeding of fish involves two options. One is to feed 
the fish to satiation (i.e. Ad libitum) and the other is to feed a restricted ration (Suresh, 
2003). Best growth is normally achieved by feeding to satiation. However, satiation 
levels are not necessarily the most economic feeding levels, as food conversion at 
satiation levels is often poor. This may also lead to overfeeding, which is wasteful and 
deleterious to water quality. As a result, restricted rations are recommended for feeding 
fish (Suresh, 2003). It is also common practice to feed to satiety before determining the 
rate of feeding. It is generally known that smaller fish consume more feed per unit body 
weight compared to larger fish. Tilapia is known to consume less feed during the colder 
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months of the year in countries where there are substantial seasonal temperature 
fluctuations. Some recommended feeding schedules widely used for semi-intensive and 
intensive culture for tilapia in freshwater ponds in China are shown in Table 2.2 (Miao 
and Liang, 2007). 
 
Table 2.2   Feeding schedules for various sizes of tilapia in semi-intensive and intensive culture 
     in freshwater ponds 
Fish size (g) 
 
 
<1 
Feeding rate (% wet body weight) Feeding frequency 
Semi-intensive 
(<20 000/ha) 
Intensive 
 (>20 000/ha) 
(No./day) 
30-10 - To satiation 
1 to 5 10 to 6 - 6 
5 to 20 6 to 4 - 4 
20-100 4 to 3 - 4 
100-250 3 - 3 
250-500 3 to 2 2.0-1.5 3 
>500 2-1.5 1.5-1.3 3-2 
Source: Adapted from Miao and Liang (2007) 
 
2.14 Nutritional Requirements of Nile Tilapia 
Nutritional requirements of fish differ for different species and more importantly vary 
with life stage. Fry and fingerlings require diets with higher protein, lipids, vitamins and 
minerals and lower carbohydrates as they are developing muscle, internal organs and 
bones with rapid growth (Fitzsimmons, 1997). From various studies the protein 
requirements of juvenile tilapia have been reported to range between 30-56% (Agbo, 
2008; Suresh, 2003; Jauncey, 1998). 
 
Protein requirements of Nile tilapia for optimum growth are dependent on dietary protein 
quality/source, fish size or age and the energy contents of the diets and have been 
reported to vary from as high as 45-50 percent for first feeding larvae, 35-40 percent for 
fry and fingerlings (0.02-10 g), 30-35 percent for juveniles (10.0-25.0 g) to 28-30 percent 
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for on-growing (>25.0 g) (El-Sayed , 2006; Lim and Webster, 2006; Fitzsimmons,  2005; 
Shiau, 2002) (Table 2.3). The broodfish require about 40-45 percent protein for optimum 
reproduction, spawning efficiency and for larval growth and survival. Nile tilapia 
requires the same ten essential amino acids (EAAs) as other finfishes. The recommended 
EAAs for Nile tilapia are shown in Table 2.4 below: 
 
Table 2.3 Dietary protein needs for Nile tilapia, O niloticus by life stage  
Life stage Weight (g) Dietary protein content (%) 
First feeding larvae  45-50 
Fry 0.02-1.0 40 
Fingerlings 1.0-10.0 35-40 
Juveniles 10.0-25.0 30-35 
Adults 25.0-200.0 30-32 
 >200 28-30 
Broodstock   40-45 
Data source: El-Sayed (2006), Lim and Webster (2006), Fitzsimmons (2005), Shiau (2002) 
 
 
Table 2.4   Essential amino acid needs of Nile tilapia, O. niloticus as % of dietary protein and of     
                  total diet 
Amino acid % of protein % of diet 
Arginine  4.20 1.18 
Histidine 1.72 0.48 
Isoleucine 3.11 0.87 
Leucine 3.39 0.95 
Lysine 5.12 1.53 
Methionine 2.68a 0.75 
Phenylalanine 3.75b 1.05 
Threonine 3.75 1.05 
Tryptophan  1.00 0.28 
Valine  2.80 0.78 
 (a) In the presence of cystine at 0.54% of dietary protein. Total sulphur amino acid (methionine plus 
cystine) requirement is 3.21% of the protein 
(b) In the presence of tyrosine at 1.79% of dietary protein. Total aromatic amino acid (phenylalanine 
plustyrosine) requirement is 5.54% of the protein 
Data source: El-Sayed (2006), Lim and Webster (2006), Fitzsimmons (2005), Shiau (2002) 
 
The minimum requirement of dietary lipids in tilapia diets is 5 percent but improved 
growth and protein utilization efficiency has been reported for diets with 10-15 percent 
lipids (Ng and Chong, 2004).  Both n-3 and n-6 polyunsaturated fatty acids (PUFAs) 
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have been shown to be essential for maximal growth of hybrid tilapia (O. niloticus x O. 
aureus). For Nile tilapia the quantitative requirement for n-6 PUFA is around 0.5-1.0 
percent.  Unlike marine fish species, tilapia appear not to have a requirement for n-3 
highly unsaturated fatty acids (HUFAs) such as EPA (20:5n-3) and DHA (22:6n-3) and 
its n-3 fatty acid requirement can be met with linolenic acid (18:3n-3). The recommended 
crude lipid, essential fatty acids and energy for Nile tilapia are shown in Table 2.5 below: 
 
Table 2.5   Crude lipid, essential fatty acids and energy needs for growth of O. niloticus (% dry 
                  feed) 
    Nutrient Amount 
Crude lipid, % min.  10-15 
 
Essential fatty acids, % min. 
 
18:2n-6  0.5-1.0a 
20:4n-6  1.0a 
18:3n-3   
20:5n-3   
22:6n-3   
 
Carbohydrate, % maxb 
 40 
 
Crude fibre, % max 
 8-10 
 
Protein to energy ratio  
 110c 
(mg/kcal)  120d 
(a) 1% 20:4n-6 or 0.5-1% 18:2n-6. 
(b) Dieatry utilization of carbohydrate appear to decrease with decrease in fish size 
(c) mg protein for kcal of gross energy (GE); (d) mg protein for kcal of digestible energy (DE) 
Data source: El-Sayed (2006), Lim and Webster (2006), Fitzsimmons (2005), Shiau (2002) 
 
Carbohydrates are included in tilapia feeds to provide a cheap source of energy and for 
improving pellet binding properties. Tilapia can efficiently utilize as much as 35-40 
percent digestible carbohydrate (El-Sayed, 2006). Nile tilapia is capable of utilizing high 
levels of various carbohydrates of between 30 to 70 percent of the diet. It has also been 
demonstrated that larger hybrid tilapia (O. niloticus x O. aureus) utilized carbohydrates 
better than smaller sized fish. Older fish seem to cope with higher dietary fibre content, a 
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maximum of 8-10 % (El-Sayed, 2006; Lim and Webster, 2006; Jauncey, 1998) and 
younger ones at about 6-8 % (Fitzsimons, 2005; Shiau, 2002). 
 
Table 2.6   Mineral requirements of O. niloticus (% of dry feed except otherwise mentioned) 
Minerals                                                                                                                                       Amount 
Macro elements (%)    
 
Calcium, max.  0.7a 
Phosphorus, min.  0.8-1.0 
Magnesium, min. 
Sodium, min. 
 0.06-0.08 
Potassium   0.21-0.33b 
 
Microelements, min mg/kg dry diet 
Iron   60 
Sulphur    
Chlorine    
Copper  2-3 
Manganese  12 
Zinc   30-79 
Cobalt   
Selenium   0.4 
Iodine   1.0 
Molybdenium   
Chromium  139.6b 
Fluorine    
aBased on data from O. aureus; bBased on data from hybrid tilapia (O. niloticus X O. aureus). 
Data source: Shiau (2002), Fitzsimmons (2005), El-Sayed (2006), Lim and Webster (2006) 
  
There is little information on the mineral requirements of tilapia.  Like other aquatic 
animals, tilapias are able to absorb minerals from the culture water which makes the 
quantitative determination of these elements difficult to carry out (Stickney, 1997). 
Despite its ability to absorb minerals from the culture water and the presence of minerals 
in feed ingredients, tilapia feeds should contain supplemental mineral premixes. This is to 
ensure that sufficient levels are available to protect against mineral deficiencies caused by 
reduced bioavailability such as when plant phosphorus sources are used in tilapia feeds 
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(Shiau and Su, 2003). The mineral requirements of Nile tilapia as percentage of dry feed 
is shown in Table 2.6 above. 
 
Table 2.7   Vitamin needs of O. niloticus (% of dry feed except otherwise mentioned) 
Vitamin   Amount 
Vitamins, min IU/kg dry diet   
 
Vitamin A (Retinol) 
 5 000 
Vitamin D (Cholecalciferol)  3.75b 
 
Vitamin, min mg/kg dry diet 
  
   
Vitamin E (α-tocopherol)  50-100c 
Vitamin K  4.4 
Vitamin B1 (Thiamine)  4 
Vitamin B2 (Riboflavin  5-6
d 
Vitamin B3 (Niacin/nicotinic acid)  26-121
b 
Vitamin B5 (Pantothenic acid)  10
a 
Vitamin B6 (Pyridoxine)  1.7-9.5
e 
Vitamin B9 (Folic acid)  0.5 
Vitamin B12 (Cyanocobalamin 
acid) 
 Not required 
Choline   1 000b 
Inositol   400b 
Vitamin B7 (Biotin)  0.06
c 
Vtamin C (Ascorbic acid)  420 
aBased on data from O. aureus; bBased on data from hybrid tilapia (O. niloticus X O. aureus). 
cBased on diets with 5% lipid. Vitamin E requirement increases to 500 mg/kg dry diet at 10-15% 
dieatry lipid level; dBased on data from hybrid tilapia (O. mossambicus X O. niloticus) and O. aureus 
eBased on data from hybrid tilapia (O. niloticus X O. aureus) at dietary protein level of 28%, requirement 
15-16.5 mg/kg diet at 36% protein diet 
Data source: Shiau (2002), Fitzsimmons (2005), El-Sayed (2006), Lim and Webster (2006) 
 
 
Vitamin supplementation is not necessary for tilapia in semi-intensive farming systems, 
while vitamins are generally necessary for optimum growth and health of tilapia in 
intensive culture systems where limited natural foods are available (El-Sayed, 2006; Lim 
and Webster, 2006). The vitamin requirements of Nile tilapia as percentage of dry feed is 
shown in Table 2.7 above. 
 
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2.15 Nutritional Deficiencies in Nile Tilapia 
Deficiency signs of farmed tilapia may occur when fish are fed nutrient deficient diets or 
raised in a low nutrient-input culture system (Dabrowska et al., 1989).  Essential amino 
acid (EAA) deficiency in tilapia generally leads to loss of appetite, retarded growth, and 
poor feed utilization efficiency (Table 2.8).   
 
Table 2.8   Dietary nutritional deficiency of essential amino acid and essential fatty acid 
EAAs/EFA Deficiency signs/syndrome 
EAAs 
Lysine  
 
Dorsal/caudal fin erosion, retarded growth, increased mortality 
Methionine  Retarded growth, cataract  
Tryptophan  Retarded growth, scoliosis, lordosis, caudal fin erosion 
Essential fatty acid 
Linoleic acid (18:2n-6) 
 
Retarded growth, swollen pale liver, fatty liver 
In bold: Reported EFA deficiency signs for O. niloticus, not in bold: general EAA deficiency symptoms in 
fish 
Data source: Tacon (1987), Tacon (1992) 
 
In some fish species (e.g. rainbow trout, sockeye salmon, Atlantic salmon, chum salmon, 
coho salmon), lysine, methionine or tryptophan deficiency results in various signs such as 
scoliosis, lordosis, fin erosions and cataracts although none of these deficiency signs have 
been reported for tilapias (Tacon, 1987).   Similar to EAA deficiency, the lack of 
essential fatty acids (EFA) will also lead to loss of appetite and poor growth in tilapia.  
Other reported signs of EFA deficiencies in Nile tilapia include swollen pale and fatty 
livers (Tacon, 1992).  
 
Mineral deficiencies are difficult to assess in tilapia as most trace elements are obtained 
both from the dietary ingredients and from the culture water (Dabrowska et al., 1989). 
Table 2.9 below shows the dietary nutritional deficiencies of some minerals in fish. 
 
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Table 2.9   Dietary mineral deficiency signs and symptoms associated with tilapia species 
Minerals  Deficiency signs/syndrome 
Phosphorus  Lordosis, poor growth 
Calcium  Reduced growth, poor feed conversion and bone mineralization 
Potassium  Reduced growth and feed efficiency, anorexia, convulsions 
Magnesium  Reduced growth/whole-body hypercalcinosis 
Iron  Microcytic, homochronic anaemia 
Zinc  Reduced growth and appetite, cataracts, high mortality, erosion of fins and 
skin, short body dwarfism, fin erosion 
Manganese  Reduced growth and skeletal abnormalities, anorexia, loss of equilibrium 
Copper  Reduced growth, cataracts 
Selenium  Increased mortality, muscular dystrophy, reduced growth, cataracts, anaemia 
Iodine  Thyroid hyperplasia (goitre) 
In bold: Reported deficiency signs for O. niloticus, Not in bold: general mineral deficiency symptoms in 
fish 
Data source: Chow and Schell (1980), Tacon (1987), Tacon (1992), NRC (1993), Jauncey (2000)
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Table 2.10   Specific vitamin deficiencies associated with tilapia species  
Vitamins  Species  Deficiency signs/syndrome 
Vitamin B2 (Riboflavin) O. aureus Poor growth, high mortality, lethargy, fin erosion, anorexia, loss of body 
colour, dwarfism, cataracts 
Vitamin B5 (Pantothenic acid) O. aureus Poor growth, hyperplasia of epithelial cells of gill lamellae, fin erosion, 
haemorrhage, anaemia, sluggishness 
Vitamin B3 (Niacin/nicotinic acid) Hybrid tilapia (O. 
niloticus x O. aureus) 
Haemorrhage, deformed snout, gill oedema, and skin, fin, and mouth 
lesions 
Vitamin B1 (Thiamine) Hybrid tilapia (O. 
mossambicus x O. 
niloticus) and Nile 
tilapia 
Poor growth and poor feed efficiency, anorexia, light colouration, nervous 
disorders, low haematocrit and red blood cell count, and increased serum 
pyruvate 
Vitamin B6 (Pyridoxine) Hybrid tilapia (O. 
niloticus x O. aureus) 
Poor growth and poor feed efficiency, high mortality, abnormal 
neurological signs, anorexia, convulsions, caudal fin erosion, mouth lesion  
Vitamin B7 (Biotin) Hybrid tilapia (O. 
niloticus x O. aureus) 
Poor growth 
Folic acid Nile tilapia Poor growth, reduced feed intake and efficiency 
Vitamin B2 (Riboflavin) Nile tilapia Requirement not reported 
Choline Hybrid tilapia (O. 
niloticus x O. aureus) 
Poor growth and survival, and reduced blood triglyceride, cholesterol, and 
phospholipid concentration 
Inositol Nile tilapia Requirement not reported 
Vitamin C (Ascorbic acid) Nile tilapia Poor growth and poor feed efficiency, scoliosis, lordosis, poor wound 
healing, haemorrhage, fin erosion, anaemia exopthalmia and gill and 
operculum deformity  
Vitamin A (Retinol) Nile tilapia Poor growth and poor feed efficiency, restlessness, abnormal swimming, 
blindness, exophthalmia, skin, fin, and eye haemorrhages, pot-belly 
syndrome, reduced mucus, secretion, high mortality 
Vitamin D (Cholecalciferol) Hybrid tilapia (O. 
niloticus x O. aureus) 
Poor growth and poor feed efficiency, low haemoglobin, , reduced liver size 
Vitamin K Nile tilapia Requirement not reported  
Vitamin E (α-tocopherol) Nile tilapia Poor growth and poor feed efficiency, anorexia, skin and fin haemorrhage, 
muscle degeneration, depigmentation 
Data source: Jauncey (2000), El-Salyed (2006), Lim and Webster (2006)   
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Under culture conditions, vitamin deficiency signs are not a common occurrence in 
tilapia (El-Sayed 2006; Lim and Webster 2006; Jauncey, 2000). In fact, several studies 
have reported on the “non-essentiality” of adding vitamin premixes to tilapia diets 
(Jauncey, 2000). Vitamins obtained from natural food in fertilized ponds, endogenous 
vitamins present in feed ingredients used in tilapia feeds and the microbial biosynthesis 
of some vitamins in the gut are all likely to contribute significantly to the vitamin 
requirements of tilapia. Table 2.10 shows the dietary nutritional deficiencies of some 
vitamins in fish. 
 
2.16 Pond Culture  
Pond culture is a very popular aquaculture production method with many aquatic species 
cultured in ponds. To have successful pond production, ponds must be properly sited and 
built, with careful assessment of water availability, quantity, and quality. There are two 
main types of pond systems: watershed and levée systems (Whitis, 2002). The climate 
and topography of a region will determine which type of pond system is appropriate. 
Areas that have enough rainfall to fill and keep ponds filled will be more suited to 
watershed pond systems. In an area where the main water source is groundwater, then a 
levée pond may be more suitable (Whitis, 2002). 
 
Most commercially produced warm-water species, some cool-water species, and baitfish 
are typically reared in ponds (Tucker et al., 2002). In commercial pond culture, there is 
either some degree of fertilization or supplemental feeding to increase production to 
commercially viable levels, greater than would occur naturally. Ponds differ from flow-
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through systems in that they are basically static and do not rely on water replacement to 
maintain water quality. Ponds rely mainly on internal natural processes to purify the 
water (Tucker et al., 2002). The biological community acts upon the dissolved wastes and 
helps to stabilize and recycle waste. Settled solids accumulate and undergo microbial 
decomposition in the pond sediment, much in the same way that a municipal water 
treatment facility functions. 
 
A pond’s production capacity is directly related to the daily amount of feed that can be 
added to the pond while still maintaining adequate water quality. As pond production 
intensifies, supplemental aeration must be used to maintain acceptable water quality 
(Tucker et al., 2001). Cole and Boyd (1986) pointed out that truly significant 
improvements in water quality appear possible only by reducing daily feeding rates to 
value less than about 50 kg/ha/day. Pond water quality needs to be well-managed and 
balanced by aquaculturists for their crops to survive and grow well (Tucker et al., 2002; 
Tucker, 1998). 
 
Pond culture is still the most commonly used method of raising tilapia (Stickney, 2000). 
One of the big advantages with a pond culture is that is closely resembles the life of wild 
tilapia and makes it possible for the fish to feed on naturally occurring food. 
Unfortunately, tilapia loves to spawn in ponds and the number of fry and fingerlings can 
rapidly reach large quantities if male and female fish are kept together. This will result in 
a situation where fry and fingerlings compete for food with the adults, resulting in a 
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lower growth speed for the fish in the pond. One way of solving the problem is to 
cultivate male fish only in the pond (Stickney, 2000).  
 
2.17 Use of Hapa in Fish Rearing 
Hapas are constructed of netting material which is sewn together to form a square or 
rectangular enclosure. Hapas differ in size and mesh according to use. Breeding hapas 
hold tilapia broodstock and are constructed of netting which has a mesh size of 1.6 to 2.0 
mm (Little and Hulata, 2000). Inverted mosquito nets are often used for this purpose, but 
the fine mesh will become clogged with plant growth if not cleaned frequently. Clogging 
prevents fresh water from circulating into the hapa and can result in a low oxygen 
condition which kills fish. Larger mesh sizes allow greater water exchange in the hapa, 
and are used for nursing fingerlings stocked at high densities. A cover is often attached 
over the hapa to prevent larger fish from jumping out and keeps predatory birds from 
injuring fish or picking relatively smaller ones (Little and Hulata, 2000). 
  
Hapas can be used in every phase of tilapia culture from fingerling production to growing 
market size food fish (Mandal and Shrestha, 2001). Hapas protect fish from predators and 
allow high survival. Produced fry and fingerlings are transferred to ponds, other hapas or 
tanks for further grow-out (Costa-Pierce and Hadikusumah, 1995; Guerrero and Garcia, 
1983). 
 
Experience with fish culture in hapa indicates that the device has the versatility for use in 
solving most of the problems encountered in farming fish. For example, the problem 
commonly faced in pond culture in Bangladesh is multiple ownerships of ponds. This can 
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be easily solved by farming fish in hapa (Hasan et al., 2010). This ensures that one is 
confined to one’s own area of the pond demarcated by mutual arrangement with co-
shares. 
 
Hapa fouling is one of the major problems for the hapa-based system (Bhujel, 2000). It 
reduces the exchange of water (Claereboudt et al., 1994; Littlewood, 1990; Paul and 
Davies, 1986) affecting natural food availability (Claereboudt et al., 1994; Paul and 
Davies, 1986) and dissolved oxygen levels (Dubost et al., 1996; Claereboudt et al., 
1994). Algae, fish faeces and particulate materials suspended in water column are the 
major causes of the fouling (Dubost et al., 1996).  
 
2.18 Hapa-Cum-Pond Culture System 
Pond production systems in many countries are becoming increasingly reliant on external 
resources (feed and/or fertilizer) to supplement or autochthonous food production for fish 
(Hasan et al., 2010). Such a system often discourages small-scale poor farmers because 
of low returns on investment. On the other hand, such poor farmers have limited financial 
resources to turn their whole ponds to culture high-valued species using expensive 
artificial feeds. However, the hapa-cum-pond fish culture system may provide an 
opportunity for small-scale farmers to use their limited resources, to include small 
amount of high-valued species in their ponds, to generate more income and improve their 
livelihood (Hasan et al., 2010). This is achieved through improved nutrient utilization 
efficiency, marketing high-valued species and saving fertilizer cost because fish in open 
pond can efficiently utilize hapa wastes and almost no fertilization required. Also this 
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hapa-cum-pond system is eco-friendly due to less waste nutrients released to the 
environment (Hasan et al., 2010).  
 
Hapa-cum-pond culture system has been developed and practised using combinations of 
catfish-tilapia and tilapia (Lin and Diana, 1995; Lin, 1990) and tilapia-tilapia (Yi and Lin, 
2001 and 2000; Yi, 1997; Yi et al., 1996). The nutrient utilization efficiency could reach 
more than 50 % in hapa-cum-pond system, resulting in the release of much less nutrients 
to the surrounding environment (Yi, 1997).  
 
2.19 Water Quality in Aquaculture 
The proper balance of physical, chemical and biological properties of water in ponds, 
lakes and reservoirs is an essential ingredient for successful production of fish and other 
aquatic resources (Mostafa, 2005). Fish are totally dependent upon water to breathe, feed 
and grow, excrete wastes, maintain a salt balance, and reproduce; for these reasons 
understanding the physical and chemical qualities of water is critical to successful 
aquaculture (Swann, 1997). For fish production, water is always a limiting factor. Both 
the quality and quantity of water available has to be in major concern for the site 
selection (Swann, 1997).  
 
Optimal water quality varies by species and must be monitored to ensure growth and 
survival (Svobodová et al., 1993). Water quality parameters that are commonly 
monitored in the aquaculture industry include temperature, dissolved oxygen, pH, 
alkalinity, hardness, ammonia, and nitrites (Svobodová et al., 1993). Any changes of 
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these parameters may affect the growth, development and maturity of fish. Some 
parameters such as alkalinity and hardness are fairly stable, but others like dissolved 
oxygen and pH fluctuate daily (Svobodová et al., 1993). Table 2.11 indicates the water 
quality preferences for some commonly cultured fish species. 
 
Table 2.11   Water quality tolerance by some commonly cultured fish species 
Species Temp 
(OC) 
Dissolved 
Oxygen 
(mg L-1) 
pH Alkalinity(mg L-1) Ammonia 
(%) 
Nitrite 
(mg L-1) 
Baitfish 16-24 4-10 6-8 50-250 0-0.03 0-0.6 
Catfish/Carp 18-27 3-10 6-8 50-250 0-0.03 0-0.6 
Hybrid Striped 
Bass 
21-29 4-10 6-8 50-250 0-0.03 0-0.6 
Perch/Walleye 10-18 5-10 6-8 50-250 0-0.03 0-0.6 
Salmon/Trout 7-20 5-12 6-8 50-250 0-0.03 0-0.6 
Tilapia  24-34 3-10 6-8 50-250 0-0.03 0-0.6 
Tropical  20-29 4-10 6-8 50-250 0-0.03 0-0.5 
Data source: Adapted from Tarazona and Munoz (1995), Svobodová et al. (1993), Boyd (1990) 
 
2.19.1 Water Quality Parameters for Tilapia 
Tilapias are also easily cultured fish in that they grow fast, are resistant to diseases and 
handling, easy to reproduce in captivity and able to tolerate a wide range of 
environmental conditions (Suresh, 2003; Shiau, 2002). Some of the cultured species have 
been shown to survive dissolved oxygen concentration of 0.1 mg L-1 and tolerated 
unionized ammonia concentration of 2.4 mg L-1 (Lovell, 1998). Although tilapias are 
typically fresh water, they are euryhaline and able to grow well in saline water if properly 
acclimated. However, their activity and feeding become reduced below 20 oC and feeding 
stops around 16 oC (Lovell, 1988). Suitable ranges of water quality parameters for tilapia 
to survive are shown in Table 2.12. 
 
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Table 2.12   Water quality parameters for tilapia 
Parameters   Tolerance range* Desirable level+ 
Temperature, oC  12-35 26-32 
Salinity, ppt  3-25 0-20 
pH  5-10 6.5-8.5 
Dissolved oxygen, mgL-1  2.0-8.0 >3.0-5.0 
Ammonia, mgL-1  0.0125 <1.0 
Nitrite, mgL-1  0.1-0.2 - 
Nitrate, mgL-1  0.0-3.0 - 
Alkalinity, mgL-1  >20 >20 
Hardness, mgL-1  >20 <50 
Data Source: Agbo, 2008; *Adapted from (Swann, 2007, Hussain, 2004; Popma and Masser, 1999; 
Stickney R.R. 1979); + (Suresh, 2003)  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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CHAPTER 3.0 METHODOLOGY 
3.1 Selection of Study Area for Survey of Fish Feed Ingredients and Commercial 
      Fish Diets 
Data on small-scale (production from 10 to 20 metric tonnes per annum) pond fish 
farmers per Region of Ghana for 2011 were obtained from the Fisheries Commission 
Head Office, Accra. Surveys of fish feed ingredients and commercial fish diets were 
conducted in the five major small-scale pond fish farming Regions in terms of number of 
farmers (Table 3.1). 
                   
Table 3.1   Number of pond fish farmers in Ghana on regional basis in 2011 
Region No. of Pond Farmers 
Ashanti 320 
Brong-Ahafo 829 
Central 180 
Eastern - 
Greater Accra 57 
Northern 4 
Upper East 20 
Upper West - 
Volta 97 
Western 240 
Total 1 747 
                           Source: Adapted from Fisheries Directorate 2011 Annual Report 
 
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The Regions were Ashanti, Brong Ahafo, Central, Western and Volta (Figure 3.1).   The 
survey was carried out during a period of eight months (December, 2012-July, 2013). 
 
 
Figure 3.1 Map showing the five Regions in Ghana (where the survey of fish feed ingredients 
                    and commercial fish diets were conducted are indicated by the red spots) 
 
3.2 Pre-Survey of Fish Feed Ingredients and Commercial Fish Diets Activities   
Interviews with fish farmers were preceded by preparation and testing of the interview 
schedule, and training of field assistants. The pre-survey activities included 
reconnaissance for the pilot survey, revision of survey instruments and preparation of the 
sampling frame. An Interview guide was prepared following personal visits to some fish 
farms and interactions with fish farmers. An informed consent form (Appendix I) was 
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prepared which explained the objectives and rationale of the survey. The form also spelt 
out the description of procedure and prospective interviewees were assured of the 
confidentiality of any information they would provide.   
 
3.3 Data Collection 
List of fish farmers in active production were obtained from the Regional Fisheries 
Offices in the five selected Regions. Standardised and structured interview guide 
(Appendix II) was administered to gather data from fish farmers who were in active 
production.  A total of 147 fish farmers were interviewed from all the five regions 
surveyed for in-depth data collection. 27 farmers were interviewed in Ashanti, 44 in 
Brong Ahafo, 20 in Central, 38 in Western and 18 in the Volta.   
 
Interview with fish farmers were mainly conducted in their houses and/or farm sites.  
Interview with each farmer lasted at least an hour and was focused on location of 
farm/farmer, bio-data, livelihood/household, fish farming culture practice, productivity, 
production constraints and fish diets as well as fish feed ingredients. In certain districts of 
some of the Regions, farmers were met in groups (Plate 3.1), and after the purpose for the 
survey and the objectives were explained to them, they were interviewed individually 
with the help of field assistants. Following the interview guide, farmers were posed 
questions and their responses were recorded. In cases where the interviewee did not 
understand English language, the assistance of interpreter was solicited. Further, visits 
were made to selected farms to observe farming practices.  
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     Plate 3.1  Interaction with fish farmers in the Prestea Huni-Valley District of Western Region, 
                     Ghana 
  
To validate the information gathered from the interview, it was cross-checked with key 
informants. A key informant is someone with special knowledge on a particular topic. 
Key informants are expected to be able to answer questions about the knowledge and 
behaviour of others, and about the operations of the broader system (Ahmed and Garnett, 
2010). These were Regional Fisheries Directors, Fisheries Extension Officers, 
Aquaculture Research Scientists, fishmongers, commercial fish diet retailers, feed 
ingredient retailers and relevant food processors. Where data was found to be 
contradictory, additional assessments were carried out. A total of 31 key informants were 
interviewed in their offices, homes and/or at their workplaces. A check-list was created to 
indicate the use of commercial fish diets and ingredients in the various Regions of the 
survey. 
 
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3.4 Selection of Feed Ingredients and Commercial Fish Diets  
The ingredients used in the formulations and preparations of the various diets were 
selected based on the findings of the regional survey. Six commonly used ingredients in 
the five regions surveyed were selected based on their nutritional value, availability all 
year round and costs. These were cassava (Manihot esculenta) flour, white maize (Zea 
mays), fish meal (Rastrinneobola argentea), soybean (Glycine spp) meal, wheat 
(Triticum aestivum) bran, and palm oil (Elaeis quineensis). The ingredients were found to 
be locally available in all regions of Ghana. Broiler vitamin-mineral premix, L-lysine, L-
methionine and common salt (iodized table salt) were included as additives/supplements. 
The two most commonly used commercial fish diets were also selected. These were 
Raanan (30 % crude protein) and Coppens (34 % crude protein).  
 
3.5 Procurement of Selected Feed Ingredients and Commercial Fish Diets 
The selected ingredients and diets were purchased at locations that were in close 
proximity to Akosombo in the Eastern Region of Ghana where the diet preparation and 
growth study were carried out. All the ingredients and additives/supplements except the 
cassava flour, palm oil and common salt were purchased from feed ingredients dealers at 
Ashaiman Timber Market located in the Greater Accra Region of Ghana. The cassava 
flour, palm oil and common salt were obtained from the Akosombo market. The 
ingredients were packaged in linen bags except the cassava flour and the additives which 
were in plastic bags. The palm oil was in a plastic gallon. Coppens and Raanan fish diets 
were purchased from their respective producers’ retail shops at Atimpoku, a town located 
on the outskirts of Akosombo. The production date of Coppens was October 8, 2013 
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whilst that of Raanan was September 4, 2013. The batch numbers of the diets were 
258913 and WF40113190400 for Coppens and Raanan respectively. 
 
3.6 Storage of Ingredients and Commercial Fish Diets 
After the procurement, the ingredients, diets and additives/supplements were labelled 
accordingly and stored in a well-ventilated room with daily ambient temperatures ranging 
from 28-34 o C during the dry season. Samples of all the ingredients and the two 
commercial diets were sent to the Animal Nutrition Laboratory of the School of 
Agriculture of the University of Cape Coast for proximate analyses so as to determine 
their proximate compositions. 
 
3.7 Determination of the Proximate Compositions of Ingredients and Diets 
Proximate analyses of the selected commercial fish diets and feed ingredients for the 
study were done following the procedures that broadly adhere to the Association of 
Official Analytical Chemists (AOAC, 1995). The protocol was applied in the 
determination of the percentage (%) dry matter (DM), % crude protein (CP), % ash, % 
crude lipid (CL) also known as ether extracts (EE) and % crude fibre (CF).  
 
3.7.1 Moisture and Dry Matter Determination 
The moisture content of each sample was determined by weighing 3.0 g of sample into a 
dry pre-weighed crucible in triplicates. The weighed samples were then dried in an oven 
at 105 oC for 24 hours. The gravimetric measurement of water in the samples was 
expressed as a percentage of the initial weight of the samples. The weight of the samples 
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after drying was expressed as a percentage of that of the initial samples to obtain the 
percentage of dry matter as follows:           
                                       Weight of sample taken – Weight of sample after drying 
            % Moisture =                                                                                                             x 100 % 
                                                             Weight of sample taken                               (AOAC, 1995) 
 
 
                                             Weight of sample after drying  
            % Dry Matter =                                                                       x 100 %         (AOAC, 1995) 
                                                   Weight of sample taken 
 
3.7.2 Ash Determination 
Ash is a measure of the total inorganic matter by incineration (AOAC, 1995). 
Approximately 2.5 g of each sample was weighed in triplicates in pre-weighed crucibles 
and incinerated for about 12 hours overnight at 600 oC using a Gallenkamp muffle 
furnace size 2. The crucibles and their contents were removed and cooled in a desiccator 
and then weighed afterward. The increase in the final weights of the crucibles represented 
the ash and was expressed as percentage of the original sample using the formula: 
 
                                                Weight of ash 
                       % Ash =                                                           x 100 %    (AOAC, 1995) 
                                              Weight of original sample 
 
3.7.3 Crude Protein Determination 
The Micro-kjeldahl method (AOAC, 1995) was used for the determination of % CP of 
samples in triplicates.  An amount of 0.2 g of each sample was weighed into numbered 
kjeldahl flasks and 4.5 ml of concentrated sulphuric acid was added. The flasks were then 
placed in the digestion block (BD-20) under a fume hood and the temperature of the 
digester was gradually increased to about 370 oC. Samples were allowed to heat overnight 
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till the solution became colourless, indicating that the digestion was completed. The 
digestion flasks were allowed to cool and the digests poured into 100 ml volumetric 
flasks and made up to volume with distilled water.  About 20 ml of the digests were 
pipette into the steam section of distillation apparatus, and then 10 ml of alkaline mixture 
was added. Then the apparatus was set to produce steam containing nitrogen, which was 
condensed in the condenser and trapped in 5 % boric acid.  About 50 ml of the distillates 
were collected into flat-bottomed flasks and titrated against 0.0071 M hydrochloric acid. 
The percentage nitrogen in the samples was calculated using the formula: 
 
                                    Hydrochloric acid used in titration x normality of standard acid     
%N in sample =100                                                                                                                 x 0.014 
Weight of sample used 
                                        
                                                                                                        (AOAC, 1995) 
The percentage of crude protein in the samples was determined by multiplying the 
percentage nitrogen with a factor of 6.25 (AOAC, 1995).  
 
3.7.4 Crude Lipid Determination 
The percentage crude lipids in samples were determined using Soxhlet solvent extraction 
technique. Approximately 2.0 g of air-dried samples in triplicates were weighed into a 
soxhlet extraction thimble and plugged with cotton wool. The plugged thimble with its 
content was transferred into a 50 ml capacity soxhlet extractor. A clean dry 250 ml round 
bottom flask was weighed. About 200 ml of petroleum-ether was added to the flask and 
connected to the extractor. A reflux condenser was inserted and extracted for 4-6 hours 
using a heating mantle. The flask was removed after the 6 hours and it was placed in a 
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hot air oven at 50 oC to dry off the ether. The flask was cooled in a desiccator and re-
weighed. The difference in weight was expressed as a percentage of the original samples 
as follows: 
                              
                               Weight of lipid 
% Crude Lipid   =                                    x 100 %    (AOAC, 1995) 
                                Weight of sample 
 
3.7.5 Crude Fibre Determination 
1g of defatted, dry samples in a pre-weighed Scintaglass crucible was used for crude fibre 
determination using acid-base hydrolysis in triplicates. The crucible was fitted to a 
Fibercap and run according to the manufacturer’s operating instructions. Hydrolysed and 
oven-dried sample was later ashed in the muffle furnace at 550 oC and crude fibre in the 
defatted samples was expressed as a percentage of the original undefatted samples as 
follows: 
 
                           Weight loss through Ashing 
% Crude Fibre  =                                                         x 100 %   (AOAC, 1995) 
                                 Original weight of sample 
  
3.7.6 Nitrogen Free Extracts (NFEs) Determination 
Percentage Nitrogen-free extract (% NFE) was computed using the formula:  
% NFE = % DM - (% CP + % Ash + % CL + % CF)   (AOAC, 1995) 
  
3.7.7 Phosphorus Determination  
The procedure requires the preparation of colour forming reagent and P standard 
solutions. The colour forming reagent is made up of reagents A and B. Reagent A is 
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made up of 12 g ammonium molybdate in 20 ml distilled water, 0.2908 g of potassium 
antimony tartarate in 100ml distilled water and 1L of 2.5M H2SO4. The three solutions 
were mixed together in a 2 L volumetric flask and made up to volume with distilled 
water. Reagent B was prepared by dissolving 1.56g of ascorbic acid to every 200mL of 
reagent A. A stock solution of 100  g P/mL solution was prepared from which 5  g 
P/mL solutions were made as a set of working standards of P with concentrations 0.0, 
0.1, 0.2, 0.4, 0.6, 0.8 and 1.0  g P/mL in 25 mL volumetric flasks. 2 mL aliquot of the 
digested samples was pipette into 25 mL volumetric flasks. About 2 mL aliquot of the 
blank digest was pipetted into each of the working standards to give the samples and the 
standards the same background solution. 
 
About 10 mL of distilled water was added to the standards as well as the samples after 
which 4 ml of reagent B was added and their volumes made up to 25 ml with distilled 
water and mixed thoroughly. The flasks were allowed to stand for 15minutes for colour 
development after which the absorbances of the standards and samples were determined 
using a spectrophotometer (Model CE 1021, 1000 SERIES; Make: Cecil) at a wavelength 
of 640 nm. A calibration curve was plotted using their concentrations and absorbance.  
The concentrations of the sample solutions were extrapolated from the standard curve and 
the amount of phosphorus was determined as follows: 
 
If C =  g P/ml obtained from the graph,  
                                         C x Dilution Factor 
then  g P/g (sample) =                                                  (IITA, 1985)  
                                            Weight of sample                                                
 
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3.7.8 Gross Energy (GE) Determination 
The gross energy for the feed ingredients, the commercial fish diets and formulated ones 
were computed by using the physiological  fuel values of 23.64, 39.54 and 17.15 MJkg-1 
for protein, fat and carbohydrate respectively (Ali and Al-Asgah, 2001). 
 
3.7.9 Chromic Oxide Analysis 
Chromic oxide was determined based on the method of Furukawa and Tsukahara (1966). 
100 mg of sample was weighed into a Kjeldahl flask. 5 ml of concentrated nitric acid 
were added to the flask and the mixture was boiled (using an electric mantle) gently for 
about 20 minutes (without boiling dry). After cooling the sample, 3 ml of 70 % perchloric 
acid was added to the flask. The mixture was then gently heated again until the solution 
turned from a green to an orange colour after which it was left to boil for a further 10 
minutes to ensure oxidation was complete. The solution was transferred to a 100 ml 
volumetric flask and diluted to volume. The absorbance of the solution was determined 
by spectrophotometer (UV mini-1240) at 350nm against distilled water and chromic 
oxide was computed using the formula: 
 
                                           (Absorbance - 0.0032) 
                                                        0.2089 
Chromic oxide (%) =                                                     x 100 %   (Furukawa and Tsukahara, 1966)  
                                                  Sample weight  
 
3.8 Study Area for Diet Formulation, Preparation and Evaluation 
The formulation, preparation and evaluation of the diets were carried out at Aquaculture 
Research and Development Centre (ARDEC) of Water Research Institute (WRI) of 
Council for Scientific and Industrial Research (CSIR) at Akosombo which lies between 
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latitude 60 13ʹ North and the longitude 00 4ʹ East at Akosombo in the Eastern Region of 
Ghana (Figure 3.2). 
 
 
 
 
        
Figure 3.2 WRI, ARDEC, Akosombo where the feed trials were conducted 
 
3.9 Diet Formulation and Preparation 
In all, five diets namely: A, B, C, D and E were evaluated for fish growth study. Two  
main diets, A and B were formulated using the selected ingredients. Broiler vitamin-
mineral premix (Kardelen 2 400 VM) and essential amino acids (L-Lysine and L-
Methionine) were added to diet A at 5 g kg-1 each. Common salt was added at 2 g kg-1. 
Diet B lacked premix and essential amino acids; instead the content of dietary lipid was 
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adjusted for their inclusions (Table 3.2). Diets C and D were the two commercial diets 
commonly used by small-scale pond fish farmers in the five Regions of Ghana where the 
survey was carried out. The diets were Coppens and Raanan respectively. The fifth diet, 
E was prepared by mixing diets B and D (Raanan) in a ratio of 1:1. 
 
Table 3. 2   Inclusion levels (%) of ingredients used in diets A and B and their cost per 
                   kilogramme  
Ingredients A  B  Cost of ingredient  
(GHS kg-1) 
Fish meal  25.0 25.0 2.30 
Soybean meal 26.8 26.8 2.40 
Maize (white)  27.0 27.0 0.72 
Wheat bran 5.0 5.0 0.64 
Cassava flour 10.0 10.0 1.32 
Palm oil 
Broiler vit/min. premix 
4.5 
0.5 
6.0 
- 
3.74 
6.00 
Common salt (iodized) 0.2 0.2 1.60 
L-Lysine 0.5 - 7.00 
L-Methionine 0.5 - 13.00 
  
In order to assess the apparent digestibility coefficients (ADCs) of dry matter (DM), 
crude protein (CP), crude lipid (CL) and carbohydrate of the experimental diets in vivo, 
0.5 % of chromic oxide (Cr2O3) as a marker, was incorporated into 99.5 % of each of the 
complete diets A, B, C, D and E. 
 
On the whole, the experimental diets were formulated to contain 300 g kg-1 protein, 100 g 
kg- 1 lipid and 18 kJ g-1 energy. These levels were based on requirements for juvenile and 
adult Nile tilapia (El-Sayed, 2006; Lim and Webster, 2006; Fitzsimmons, 2005; Shiau, 
2002). The diets were formulated on as-fed basis. The fish meal (Tuna fish meal, 
produced by Pioneer Food Canary, Tema) and soybean meal (locally produced) were 
used as the main dietary protein sources. The Cassava flour, Maize and wheat bran were 
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used as the main dietary carbohydrate sources. The cassava flour also served as a binder.  
The palm oil was used as the main source of lipid in the diets.   
 
The fishmeal, maize, soybean meal and wheat bran were finely milled separately using a 
corn milling machine and subsequently sieved through a 800 μm sieve to rid them of 
relatively larger sized particles. The cassava flour was not milled as it was already in a 
powdered form before it was procured. However, it was also sieved.  The dry powdered 
ingredients were weighed using top loading electronic balance (KERN EMB Version 3.1 
11/2009) into large labelled plastic bowls according to the proportion based on the 
formulation for each diet. The ingredients were mixed with the hands protected with 
disposable gloves until uniformly blended and homogenous powdered mixtures were 
obtained.  
 
Table 3.3   Composition of the vitamin-mineral premix used in diet A 
Composition  For 2 500 g 
Vitamin A 12 000 000 IU 
Vitamin D3  2 000 000 IU 
Vitamin E 40 000 mg 
Vitamin K3  4 000 mg 
Vitamin B1                3 000 mg 
Vitamin B2 6 000 mg 
Vitamin B6  5 000 mg 
Vitamin B12 20 mg 
Niacin 40 000 mg 
Cal-Pan 15 000 mg 
Folic Acid 1 000 mg 
Biotin  50 mg 
 
 
The measured quantity of broiler vitamin-mineral premix, L-lysine, L-methionine, 
common salt and palm oil were added to diet A and the mixture was mixed thoroughly. 
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The composition of the vitamin-mineral premix used in diet A is shown in Table 3.3 
above. 
 
For diet B, only common salt and palm oil were added. Between 40 – 50 % of water was 
added slowly to the mixtures with continuous stirring until dough was formed. A 32# 
Hand-Operated Meat Mincer was used to pellet the diets using a die size of 3 mm into 
strands (Plate 3.2). 
 
Plate 3.2 Using hand-operated meat mincer to pellet prepared fish diet 
 
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The two commercial diets (C and D) which were originally extruded were milled into 
powdered forms and then pelleted so as to ensure consistency in the forms and sizes of all 
the diets.   Diet E was prepared by mixing equal portions of powdered forms of Diet B 
and Diet D (Raanan) before pelleting.  Table 3.4 and 3.5 show the constituents of diets C 
and D respectively as declared by the respective producers on the labels of their bags. 
 
Table 3. 4   Constituent of Coppens (Diet C) as indicated on the label of the feed bag 
Analytical Component Percentage (%) 
Crude Protein 34 
Crude Fat 10 
Crude Fibre 3.2 
Crude Ash 8.4 
Phosphorus 0.8 
Calcium 1.0 
Sodium 0.2 
  
Additives  
Vitamin A 10 000 μg/kg 
Vitamin D3 1 000 μg/kg 
Vitamin E 200 mg/kg 
Vitamin C (Stable) 150 mg/kg 
  
Antioxidants  
E 324 Ethoxyquin 100 mg/kg 
E 321 Sutylated hydroxytclune 50 mg/kg 
  
Trace Elements  
Iron (ferrous sulphate, monohydrate) 75 mg/kg 
Iodine (Calcium iodate, anhydrous) 5 mg/kg 
Cobalt (basic cobaltons carbonate, monohydrate) 1 mg/kg 
Copper (cupric sulphate, pentahydrate) 5 mg/kg 
Manganese (manganic oxide) 20 mg/kg 
Zinc (zinc sulphate, monohydrate) 80 mg/kg 
Selenium (sodium selenite) 0.3 mg/kg 
 
Ingredients  
Wheat, soya dehulled, toasted fish meal, ranola oil, fish oil, hydrolised feather meal, palm oil, 
blood products, fish meal and/ or fish solubles  
 
 
 
 
 
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Table 3.5   Constituent of Raanan (Diet D) as indicated on the label of the feed bag 
Analytical Component Percentage (%) 
Crude Protein 30.0 
Fat   5.0 
Fibre   4.0 
Ash   8.0 
Phosphorus   1.1 
Moisture   9.0 
  
Additives  
Vitamin A   7 500 μg/kg 
Vitamin C        90 μg/kg 
Ingredients 
Products and by-products of poultry, oil seeds and cereals, vitamins and minerals 
 
The pellets were sun-dried for 8 to 10 hours to reduce the moisture content so as to 
prevent the growth of mould and consequently the pellets were broken into smaller sizes 
(between 1-2 mm) that the experimental fish could pick. The diets to be used 
immediately were put into labelled transparent plastic containers of each having a 
capacity of about 10 litres. The excess diets were then packaged in labelled polythene 
bags and stored in a well-ventilated room. Samples of the prepared diets and the 
commercial diets were analysed for proximate compositions and phosphorus as described 
in Section 3.7.  The values obtained were used to compute the energy contents of the 
various diets. Ten (10) kilogrammes of each diet type was prepared at a given time as and 
when the old stock was getting depleted.   
 
3.10 Experimental System  
Fish growth study was carried out in a 5.0 x 2.0 x 1.2 m (i.e. length, width and height) 
mosquito netting hapas. A monofilament nylon gill net of stretched mesh size 30.0 mm 
was sewn over the hapas as a cover and an opening was left at one end of the 2 m side so 
as to allow input and collection of fish during stocking, measurements and harvest. The 
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cover net was to keep predatory birds from injuring or picking the experimental fish and 
also to prevent the fish from jumping out as they grow bigger (Little and Hulata, 2000). 
The hapas were mounted in a 0.2 hectare (2 000 square metres) earthen pond at ARDEC, 
Akosombo. The pond was supplied with water from the Volta Lake to a mean height of 
about 1.4 ± 0.2 m. The hapas were suspended to bamboo poles by means of nylon twine 
and the former were inserted in the bed of the pond (Plate 3.3).  
 
 
Plate 3.3 Experimental hapas being mounted in a 0.2 hectare earthen pond at ARDEC,  
               Akosombo 
 
Each hapa was separated from others by about 6 m distance to avoid easy drifting of 
contents of one system into another.  About two-thirds (0.8 m) of the hapa heights were 
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constantly submerged in the pond water by ensuring periodic topping up of the water 
when the level fell mainly due to evaporation and seepage.  
 
The experimental system for digestibility study consisted of plastic containers (about 0.10 
m2 bottom area), each with 45.0 L total volume capacity, filled with 20.0 L of water. 
There were three replicates for each treatment. Aeration in the containers was maintained 
by the insertion of air stones. 
 
3.11 Experimental Fish 
The eighth generation of hormonal sex-reversed, all-male O. niloticus known as the 
“Akosombo Strain” developed by CSIR-WRI at ARDEC, Akosombo through selective 
breeding was used in the growth study. The hormonal sex reversal process is not 100 % 
effective. Success rates have been between 80-92 %. The process can give an excess of 
90 % male, averaging 95 % male, 100 % populations are seldom achieved (Mair et. al., 
1997). The fish were randomly taken from a batch that was sex reversed and were being 
nursed to be supplied to fish farmers when they attain 2.0 g. The stock was nursed in 
isolated hapas and were fed daily at ad libitum until they attained sizes that they could be 
hand-sexed. This was to avoid using mixed sex fish in the growth study as the females 
are known to divert large amounts of food energy to egg production (Avault and Shell, 
1968). During the nursing stage, the fish were fed twice a day with Raanan fish diet used 
at ARDEC.  
 
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3.12 Conditioning and Stocking of Experimental Fish 
The hand-sexed all-male “Akosombo Strain” O. niloticus was kept in hapas or net 
enclosures (each with dimensions 5 m x 2 m x 1.2 m). They were not fed for about 48 
hours. After which they were fed with a milled powdered mixture of white maize and 
cowpea in a ratio of 1:1 twice a day for a week. This was to completely wean them off 
the Raanan fish diet. At the end of the period, a sample of 3 fish was taken to determine 
the proximate composition.  
 
The initial Standard Length (SL), Total Length (TL) and wet weight of the individual fish 
to be stocked were measured (to the nearest 0.1 cm and 0.1 g respectively) using a fish 
measuring board and a top loading electronic balance. In all, 300 all-male O. niloticus 
were used in the growth study. The fish were without any particular sizes (i.e. randomly) 
divided into five groups of 20 fish (5 treatments in triplicate) and stocked in fifteen hapas, 
each of operational volume of about 8.0 m3 on December 14, 2013. For the plastic 
containers used in the digestibility study, the stocking was 4 fish per system.  
 
3.13 Feeding Schedule 
The experimental design used in the growth study was mainly completely randomized 
design (CRD) where the various dietary treatments were randomly assigned to the 
experimental units (hapas). Feeding of the stocked fish commenced the following day 
with the experimental diets A, B, C, D and E (i.e. the prepared diet containing lysine, 
methionine, and vitamin-mineral premix; Prepared diet without lysine, methionine and 
premix; Coppens; Raanan and a 1:1 mixture of B and D respectively). All the fish under 
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each treatment were manually fed at 4.0 % of their body weight (biomass) three times 
daily (between 0800-0830, 1200-1230 and 1600-1630 GMT) throughout the week 
including weekends.  
 
During the first week of stocking, all dead fish in each hapa under each treatment were 
replaced with live ones of similar weights. The 4.0 % rate of feeding was maintained 
until the fish in any hapa had attained a mean body weight greater than 100.0 g. Then the 
feeding rate was reduced to 3.0 %, but feeding frequency of 3 times per day was 
maintained throughout the growth study. 
 
Fish used for digestibility study were fed the chromic oxide diets, twice a day (0900 and 
1500 hours) at a rate of 6 % of their body weight per day. A 5 day acclimatization period 
was allowed, during which the faeces collected were discarded and those collected in the 
subsequent days were analysed for proximate compositions and chromic oxide. After an 
hour of diet administration, the containers were cleaned and any uneaten diet and faecal 
residues were removed from the system by siphoning with a crystal siphon of an internal 
diameter 15 mm. About three-fourth of the water in the systems was replaced with fresh 
water so as to maintain a good water quality. Siphoning of faeces and cleaning of the 
systems were done in about 45-60 minutes before feeding the fish. Faeces collected each 
day from each tank of a dietary treatment were pooled and immediately centrifuged using  
Sigma 2k15 Centrifuge at 3 800 g for 15 minutes and the supernatant discarded. Wet 
settled solids of faeces were rinsed with deionized water and stored in vials at -20 oC to 
retard bacterial decomposition. Faeces were collected for about two weeks.  The samples 
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were later defrosted and oven dried at 60 oC, ground and analysed for proximate 
composition and Cr2O3.  
 
3.14 Measurements of Fish during Growth Study  
The SL, TL and weights of all the fish in each hapa under each treatment were measured 
fortnightly as described in Section 3.12.  A bamboo pole was used by two people at the 
opposite sides of the longer side of each hapa, starting from the bottom of the sewn end 
of the cover; the pole was drawn to confine the fish at the open end of the cover. All the 
fish were then netted and put into a large bowl containing pond water. The hapas were 
cleaned with pond water to ensure water circulation. The total number of fish was 
recorded. Each fish was gently blotted on a soft towel so as to remove excess water from 
the body. Then the lengths were measured followed by the weight. Each fish was then 
returned into a bowl containing fresh pond water. After measuring the lengths and 
weights of all the fish in each hapa, they were put back into their respective hapas. The 
biomass (total weight) of fish in each hapa under each treatment was computed and 
subsequently the quantity of each diet type for each fish group was adjusted accordingly. 
The measurements were done between 0630 and 0930 GMT. The fish were not fed on the 
day they were handled, feeding commenced at 0800 GMT of the following day. The 
growth study was carried out for 20 weeks (140 days). The day after the 140 days, all the 
fish from each treatment was harvested, counted and measured individually to determine 
the final growth and survival.   A sample of 3 harvested fish (1 from each replicate) of 
each treatment was taken to determine the proximate composition.  
 
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3.15 Monitoring of Water Quality Parameters  
In the determination of the effects of feeding fish with the various diets on water quality, 
the following water quality parameters were monitored during the growth study: 
Temperature, electrical conductivity (EC), pH, total suspended solids (TSS), dissolved 
oxygen (DO), salinity, alkalinity and hardness were monitored in and around the hapas 
and the open pond waters. Nutrients such as phosphate-P, nitrate-N, nitrite-N and 
Ammonia were also determined to indicate the extent of eutrophication of the various 
hapas status by feeding the experimental fish with each of the diets. Water quality 
analyses were conducted fortnightly during the same time period of the day (0630-0800 
hours) using specified methods as laid down in Standard Methods for the Examination of 
Water and Wastewater (APHA, AWWA, WEF, 1998).   
 
Water quality parameters such as temperature, electrical conductivity, salinity, pH and 
DO were measured in situ (using a pre-calibrated Hanna HI 9828 multi-parameter meter), 
whilst alkalinity, ammonia, hardness, phosphate, nitrite, nitrate and TSS were determined 
in the laboratory (using spectrophotometer, Hach DR 2800).  
 
3.15.1 Determination of Water Quality Parameters in the Field 
All the physico-chemical parameters were measured at a depth of about 0.4 m. The probe 
of the meter was immersed into the hapa and the pond in situ and the temperature, EC, 
pH, salinity and DO were read directly from the meter when equilibrium was achieved 
(Plate 3.4). Temperature was measured in degree Celsius (o C), EC in microsiemens per 
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centimetre (μScm-1), salinity in parts per thousand (ppt) and DO in milligram per litre 
(mgl-1). 
 
 
Plate 3.4 Measuring of physico-chemical parameters in an experimental hapa in the pond 
 
3.15.2 Determination of Water Quality Parameters in the Laboratory    
For the parameters that were determined in the laboratory, three replicate samples of 
water were taken from each hapa treatment and the pond into 250 ml plastic bottles 
which were acid clean and rinsed three times with distilled water and dried in an oven. 
The samples were immediately stored in an ice-chest, stocked with ice blocks and 
maintained at a temperature of about 4 oC.  In the laboratory, the samples were thawed to 
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room temperature and various treatments were given to the samples for each parameter 
determination as follows:  
 
Alkalinity 
For the determination of the alkalinity, a sample volume of 100 mL and titration cartridge 
1.600 N H2SO4 were used. A clean delivery tube was inserted into the 1.600 N sulfuric 
acid titration cartridge. The cartridge was attached to the titrator. The delivery knob was 
turned to eject air and a few drops of titrant. The counter was reset to zero and the tip was 
wiped. A graduated cylinder was used to measure the sample and it was transferred into a 
clean 250-mL Erlenmeyer flask. The contents of one phenolphthalein indicator powder 
pillow were added and it was swirled to mix. The solution was colourless, suggesting the 
phenolphthalein alkalinity was zero. The contents of one Bromcresol Green-Methyl Red 
Indicator powder pillow were added and it was swirled to mix. The titration was 
continued with sulfuric acid to a light pink colour. The digits displayed on the counter 
were recorded as alkalinity in mgL-1 (APHA, AWWA, WEF, 1998). 
 
Ammonia 
The spectrophotometer programmed number for ammonia analysis was keyed in and set 
to 655 nm wavelength. A sample cell was filled to the 10-mL mark with the sample. A 
second sample cell was also filled to the 10-mL mark with deionized water. The contents 
of one ammonia salicylate powder pillow were added to each cell. The cells were capped 
and shook to dissolve the contents. The instrument was started and a three-minute 
reaction period was allowed. When the timer expired, the contents of one ammonia 
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cyanurate reagent powder pillow were added to each cell. The cells were capped and 
shook to dissolve the contents (APHA, AWWA, WEF, 1998). 
 
The instrument timer was started and a 15-minute reaction period began. A green colour 
developed. When the ammonia salicylate was added, a compound known as 5-
aminosalicylate was formed. It was oxidized in the presence of a sodium nitroprusside 
catalyst to form a blue-coloured compound. The blue colour was masked by the yellow 
colour from the excess reagent present to give a final green-coloured solution. When the 
timer expired, the blank was wiped and it was inserted into the cell holder. The 
instrument was zeroed and the display showed 0.00 mgL-1 NH3-N. The sample was 
wiped and it was inserted into the cell holder. The results were then read in mgL-1 NH3-N 
(APHA, AWWA, WEF, 1998).   
 
Hardness 
The spectrophotometer programmed number for phosphate analysis was keyed in and set 
to 522 nm wavelength. For the determination of total hardness, magnesium test was first 
selected. A 100 mL of the sample is poured into a 100 mL graduated mixing cylinder. A 
1.0 mL measuring dropper is used to add 1.0 mL of calcium and magnesium indicator 
solution. The cylinder is stopped and inverted several times. 1.0 mL of alkaline solution 
for calcium and magnesium test is added using a 1.0 mL measuring dropper. The cylinder 
is stopped and inverted several times. 10 mL of the solution is poured into each of three 
sample cells. One drop of 1 M EDTA solution is added to the first cell (blank) and the 
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mixture was swirled to mix thoroughly. After, one drop of EGTA solution was added to 
the second cell and the mixture was swirled to mix thoroughly  
  
The indicator dye is calmagite, which forms a purplish-blue colour in a strongly alkaline 
solution and changes to red when it reacts with free calcium or magnesium. Calcium and 
magnesium determinations are made by chelating calcium with EGTA to destroy any red 
colour due to calcium and then chelating the calcium and magnesium with EDTA to 
destroy the red colour due to both calcium and magnesium. By measuring the red colour 
in the different states, calcium and magnesium concentrations are determined. The blank 
(first cell) was inserted into the cell holder. The spectrophotometer was zeroed and the 
display showed 0.00 mg L-1 Mg CaCO3. The magnesium sample (second cell) was 
inserted into the cell holder. The results were read in mgL-1 Magnesium as Calcium 
Carbonate. This value was the amount of magnesium in the sample expressed as CaCO3. 
The results of magnesium were recorded and its programme was exited. Then calcium 
test was selected. The instrument was zeroed and display showed 0.00 m gL-1 Ca CaCO3. 
The second cell is removed and the third cell (calcium sample) was inserted into the cell 
holder. The results were read in mg L-1 calcium as calcium carbonate. This value was the 
amount of calcium in the sample expressed as CaCO3. The values of Magnesium and 
Calcium were added to obtain the total hardness (APHA, AWWA, WEF, 1998). 
 
Nitrates 
25 ml of the sample was measured into 30 ml test tubes. 25 ml of distilled water was also 
measured into a separate test tube and labelled as blank. The spectrophotometer was set 
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up and programmed to analysed nitrate at 450 nm wavelength. Nitraver 5 nitrate reagent 
was added to the 25 ml sample including the blank. As soon as the reagent was added, the 
tubes were shaken vigorously for one minute. After which they were left undisturbed for 
five minutes reaction period. 
 
The reagent which contained cadmium, induced nitrate to nitrite in the samples. The 
latter reacted with sulfanitic acid to form diazonium salt intermediate in an acid medium. 
The salt combined with gentisic acid to form amber-coloured product. At the end of the 
reaction period, the spectrophotometer was zeroed with distilled water and then the 
reading for the blank and the sample were determined. The values obtained for the blank 
were subtracted from those of the sample to obtain the actual amount of nitrate in the 
sample in milligrams per litre (mg l-1) (APHA, AWWA, WEF, 1998). 
 
Nitrites 
25 ml of the sample was measured into 30 ml test tube. 25 ml of distilled water was also 
measured into a separate test tube and labelled as blank. The spectrophotometer was set 
up and programmed to analyse nitrite at 507 nm wavelength. Nitriver 3 nitrite reagent 
was added to the 25 ml sample including the blank. As soon as the reagent was added, the 
tubes were shaken vigorously for one minute. After which they were left undisturbed for 
five minutes reaction period. 
 
Nitrite in the sample reacts with sulfanilic acid in the reagent to form an intermediate 
diazonium salt. This couples with chromotropic acid to produce a pink coloured complex 
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directly proportional to the amount of nitrite present. At the end of the reaction period, 
the spectrophotometer was zeroed with distilled water and then the reading for the blank 
and the sample were determined. The values obtained for the blank were subtracted from 
those of the sample to obtain the actual amount of nitrite in the sample in milligrams per 
liter (mg l-1) (APHA, AWWA, WEF, 1998). 
 
Phosphate 
25 ml of the sample was measured using measuring cylinder into 30 ml reaction tube as 
well as 25 ml of distilled water. The spectrophotometer programmed number for 
phosphate analysis was keyed in and set to 880 nm wavelength. Phosver 3 phosphate 
reagent was added to the sample and the mixture was swirled to mix thoroughly. After 
that, two minutes reaction period was allowed. The phosver 3 phosphate reagent contains 
molybdate and ascorbic acid. Orthophosphate which was present in the sample reacted 
with the molybdate to form phosphomolybdate complex in an acid medium. Ascorbic 
acid then reduced the complex salt to give an intense molybdenum blue colour. 
 
After the reaction time elapsed, the spectrophotometer was zeroed with distilled water, 
and values for the blank and the sample were read. The result for the blank was 
subtracted from that of the sample to obtain the actual amount of phosphate in the sample 
in mg l-1 (APHA, AWWA, WEF, 1998). 
 
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Total Suspended Solids (TSS)  
The spectrophotometer was set at 810 nm in analysing the TSS. The sample was blended 
by vigorous shaking and the instrument at zero with distilled water, whilst the sample 
was poured into the cell and the value of the TSS was read in ppt (APHA, AWWA, WEF, 
1998). 
 
3.16 Determination of Biological Parameters 
The various measurements made during the growth study using the 5 different diets and 
the results from analysis of the diets, faeces and the fish carcasses were used to determine 
the following biological parameters: 
 
3.16.1 Growth Performance 
Growth performance was evaluated by computing the mean weight gain by fish and 
specific growth rate (SGR).  
 
3.16.1.1 Mean Weight Gain (MWG) 
 The MWG is the difference between the final mean body weight and the initial mean 
body weight of fish over a period of time and it was computed as follows: 
 
                        Final mean body weight – Initial mean body weight 
  MWG    =                                                                                                 x 100 %   (Ricker, 1979)) 
                                           Initial body weight 
 
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3.16.1.2 Specific Growth Rate (SGR) 
SGR is the instantaneous change in weight of fish expressed as the percentage increase in 
body weight per day over any given time interval. It is calculated by taking natural 
logarithms of the fish body weight, and expresses growth as percentage per day (Ricker, 
1979). 
                                 In (final body weight) – In (initial body weight)  
              SGR  =                                                                                               x   100 % 
                                           Culture period (in days) 
 
3.16.2 Survival Rate (SR)  
                      Initial number of fish stocked – Total mortality 
        SR =                                                                                            x 100 % (Attipoe et al., 2009)  
                                  Initial number of fish stocked 
 
3.16.3 Feed Conversion Ratio (FCR) 
FCR is defined as the amount of dry feed fed per unit live weight gain. It often serves as a 
measure of efficiency of a diet. The more suitable a diet is for growth, less of it is 
required to generate a unit weight gain (i.e. a lower FCR) (De Silva and Anderson, 1995).  
It was computed as:  
                           Total feed fed (g) 
FCR =                                                         
                   Live weight gained by fish (g) 
 
FCRs of 1.5-2.0 are considered ‘good’ growth for most fish species (Houlihan et al., 
2001). 
 
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3.16.4 Feed Efficiency (FE) 
FE is simply the reciprocal of FCR (1/FCR). It was computed as:  
 
                Live weight gained by fish (g) 
FE  =                                                                x 100 %  =  1/FCR x 100 %                                                
                          Total feed fed (g) 
 
 
FE greater than 50 % is considered ‘good’ growth (Houlihan et al., 2001).  
 
3.16.5 Length-Weight Relationship 
The Length-Weight relationship was analyzed by using the equation W= aLb    (Pauly, 
1983; Everhart et al., 1975).  
Where: W= weight of fish in grammes (g)  
L= Length of fish in centimetres (cm) 
a = the intercept (it describes the rate of change of weight with length)  
b = the slope (the weight at unit length) 
  
The equation was log-transformed into a straight line of the form: y = mx + c, by double 
logarithmic transformation thus giving the equation as log W = b log L + Log a. By 
plotting Log W (y) against Log L (x) a straight line was obtained. From this line, the 
values b representing gradient of the straight line and a representing the intercept on the 
y-axis were estimated. When b is equal to three (3), isometric pattern of growth occurs 
but when b deviate significantly from 3, allometric pattern of growth occurs, which may 
be positive if >3 or negative if <3.  
 
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3.16.6 Condition Factor (K)                              
The condition factor or coefficient of condition (K) which is mathematical estimation of 
physiological well-being of a fish in its habitat is determined by using the equation: 
                                                                                    
                   W                                                     
K =                              x   105          (Gomiero and Braga, 2005; Tesch, 1968).                   
                   SLb                                              
 
Where: 
W = the weight of the fish in grammes (g)  
SL = the standard length of the fish in centimetres (cm)  
b = the value (the weight at unit length) obtained from the length-weight equation. 
  
The exponent ‘b’ value, that is equal to 3, was not used to calculate the ‘K’ value. Bolger 
and Connolly (1989) observed that it is not a real representation of the length-weight 
relationship for greater majority of fish species, therefore the ‘b’ value used was obtained 
from the estimated length-weight relationship equation (W = aLb) as suggested by Lima-
Junior et al. (2002). 
 
In fish, the K reflects through its variations, information on the physiological state of the 
fish in relation to its welfare. From a nutritional point of view, there is the accumulation 
of fat and gonadal development (Le Cren, 1951). K also gives information when 
following up the degree of feeding activity of a species to verify whether it is making 
good use of its feeding source (Bagenal and Tesch, 1978). 
  
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3.16.7 Energy Retention (ER)  
                           Final fish body energy – Initial fish body energy 
      ER  =                                                                                                    x 100 %   (Agbo, 2008) 
                                                   Gross energy intake   
 
 
3.16.8 Hepatosomatic Index (HSI) 
At the end of the growth study, 5 fish were randomly selected from each hapa of each 
treatment, dissected and livers removed, weighed and used to estimate the hepatosomatic 
index (HSI) using the formula (Agbo, 2008; Strange, 1996): 
                    Liver weight 
HIS  =                                           x 100 % 
                 Whole fish weight 
 
3.16.9 Protein Efficiency Ratio (PER) 
PER is defined as the ratio of the live weight gained by fish to the amount of crude 
protein fed (De Silva and Anderson, 1995). 
 
                 Live weight gained by fish (g) 
PER  =                                                        
              Crude protein of feed fed to fish (g)  
  
3.16.10 Protein Productive Value (PPV) 
The PPV also known as ‘efficiency of protein utilization’ (Gerking, 1971), evaluates the 
protein in the diet by the ratio of the protein retained in the fish tissues to the dietary 
protein fed. PPV is determined by carcass analyses of protein in fish samples before and 
after feeding them with the evaluated diet, and it is generally expressed as a percentage of 
the protein of the diet fed. 
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                   Protein retained in tissue 
PPV  =                                                         x 100 % 
                 Dietary protein consumed 
 
PPV takes into account the transformation of the dietary protein into body protein rather 
than the overall increase in body weight. Hence, it is a more refined criterion for the 
evaluation of dietary protein compared to PER (Hepher, 1988).  
 
                                               (FBW x FBN) – (IBW x IBN) 
Nutrient Deposition   =                                                                     x 100 % 
                                                (feed intake x feed nutrient) 
 
Where:  FBW = final body weight (g), 
              IBW = initial body weight (g),  
              FBN = final body nutrient and  
              IBN = initial body nutrient. 
 
As a result of practical constraints in experiments with fish, in the calculation of FCR, 
PER and PPV (ANPU – Apparent Net Protein Utilization) the amount of diet fed instead 
of that which was  consumed or intake by fish was used as it was impossible to quantify 
the un-ingested nor uneaten diet by the fish in the experimental systems. This could really 
bring about overestimation of feed and underestimation of the ratios (Agbo, 2008). 
 
3.16.11 Apparent Digestibility Coefficient (ADC) 
The ADC of CP, lipid and carbohydrate of the diets was determined using the following 
determination (Maynard and Loosli, 1956):   
 
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                                              % dietary Cr2O3      % faecal nutrient                                                         
ADCnutrient  = 100  –                                                                                     100 
                                              % faecal Cr2O3          % dietary nutrient 
 
 
The ADC of dry matter was estimated as follows (Maynard and Loosli, 1956): 
 
                                                       % dietary Cr2O3       
ADCdry matter   =   100 –   100 
                                                        % faecal Cr2O3       
 
 
3.17 State of Fish Health 
At the end of the growth study, 15 fish were selected at random from each treatment and 
their health profiles were taken using the score sheet described in Table 3.6 below, based 
on a modification of Barton et al., (2002); Adams et al., (1993); Goede and Barton 
(1990): 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Table 3.6 Criteria used at the end of the growth study for fish health observations 
Structure or tissue Rating criteria Numeric rating  
Eyes  Normal 0 
 Abnormal  1 
Fat  None  0 
 <50 % of gut covered  1 
 >50 % of gut covered 2 
 100 % of gut covered 3 
Fins  No erosion 0 
 Light erosion 1 
 Moderate erosion  2 
 Severe erosion  3 
Gills  Normal  0 
 Clubbed, frayed or discoloured 1 
Gut  Normal  0 
 Slight inflammation 1 
 Moderate inflammation 2 
 Severe inflammation 3 
Kidney  Normal  0 
 Abnormal  1 
Liver  Normal  0 
 Abnormal  1 
Pseudobranchs  Normal  0 
 Abnormal  1 
Opercles  Normal  0 
 Short  1 
Spleen  Normal  0 
 Cysts or enlarged  1 
Source: Adapted from Barnes et al., 2012. 
 
3.18 Economic Analyses of Diets 
For the assessment of the cost effectiveness of the farm-made and commercial diets used 
in the growth study, simple economic analyses were employed. The costs of the diets 
were calculated using market prices of the ingredients and commercial diets per 
kilogramme as existed in the study area.  Only the cost of the diets was used in the 
calculations with the assumption that all other operating costs (e.g. transport, hapa, 
fingerlings and labour) remained constant. However, ten percent (10 %) of the original 
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costs per kilogramme of farm-made diets A and B based on the price of the ingredients 
used was added to each diet to cover the cost of labour in the cost analyses of these diets. 
 
3.18.1 Incidence Cost (IC) 
The incidence cost was computed as:    
                    Cost of feeding (GHS) 
IC  =                                      
             Weight of fish produced (kg) 
 
 
IC is the cost of feed used to produce a kilogramme of fish (relative cost per unit weight 
gain), and the lower the value the more profitable it is using a feed (Agbo et al., 2011; 
Abu et al., 2010; Nwanna, 2003; Vincke, 1969). 
 
3.18.2 Profit Index (PI) 
The profit index was computed as: 
 
        Value of fish produced (GHS)   
PI =                                      
              Cost of feed used (GHS)  
  
The value of fish was based on the farm-gate price in the Asuogyaman District of the 
Eastern Region of Ghana, 2014. The higher the PI, the more cost effective (economical) a 
diet is (Agbo et al., 2011; Miller, 1976).  
 
3.19 Data Analyses 
Data from interviews were coded and entered into a database system using Microsoft 
Excel software (2007 version). IBM SPSS (version 19.0, SPSS Inc., Chicago, IL) was 
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used to produce descriptive statistics. All data on fish growth performance, feed 
utilisation, carcass traits digestibility and water quality were tested for normality using 
the Kolmogorov-Smirnov test and homogeneity using the Levene’s test.  The tests were 
carried out to find out if the data were normally distributed and the variances were 
homogeneous. All percentages and ratios were arcsine transformed to normalize the data 
before analyses (Zar, 1984).  Statistical analyses were carried out using one-way analysis 
of variance (ANOVA) to test differences among the various parameters of the dietary 
treatments. Tukey’s multiple range test (MRT) was used to identify specific differences 
between pairs of treatments. Differences were regarded as significant when p < 0.05. 
Regression analysis was applied to determine the relationship between length and weight 
of O. niloticus in each dietary treatment. 
 
 
 
 
 
 
 
 
 
 
 
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CHAPTER 4.0 RESULTS 
4.1 Fish Feed Ingredients Used by Fish Farmers in Ashanti, Brong-Ahafo, Central,  
      Volta and Western Region  
A check-list of feed ingredients and supplements/additives used by small-scale pond fish 
farmers in Ashanti, Brong Ahafo, Central, Volta and Western Regions and their unit cost 
are presented in Table 4.1a and Table 4.1b. In all, 34 fish feed ingredients and 5 feed 
supplements/additives were being used by small-scale pond fish farmers in farm-made 
fish diet production in all the five regions surveyed. Most of the ingredients were being 
utilized in at least three of the regions, except a few that were unique to one or two 
regions. Fish meal (Rastrinneobola argentea) (miscellaneous), Maize (Zea mays), Rice 
(Oryza sativa) bran and Wheat (Triticum aestivum) bran were being used in all the five 
regions, whilst Bean (Phaseolus vulgaris) leaves, Birds (dead poultry), Brewery waste, 
Cassava (Manihot esculenta) leaves, Coconut (Cocos nucifera) paste, Cotton (Gossypium 
spp) seed cake, Millet (Urochloa ramose), Palm fruit fibre, Pito mash, Potato (Solanum 
tuberosum) leaves, Poultry offal and Rice (Oryza sativa) were being used in only one 
region. In general, most of the ingredients were cultivated by the farmers themselves as 
most of them grow crops aside from fish farming. However, a section of them obtained 
most of the ingredients they used from food processors and feed ingredient retailers. 
There were both inter- and intra-regional differences in the price per kilogramme of all 
the ingredients. Ingredients whose unit cost is indicated by GHS 0.00 could be sourced 
off farm or the household at no cost.   
  
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Table 4.1a Checklist of utilized fish feed ingredients in Ashanti, Brong Ahafo, Central, Volta and Western Region of Ghana 
 
 
Ingredient 
Region 
Ashanti Brong Ahafo Central Volta Western 
Occurrence Cost per 
Kg 
(GHS) 
Occurrence Cost per 
Kg 
(GHS) 
Occurrence Cost per 
Kg 
(GHS) 
Occurrence Cost per 
Kg 
(GHS) 
Occurrence Cost per 
Kg 
(GHS) 
Bean (Phaseolus vulgaris) husks     0.00     0.00   
Beans (Phaseolus vulgaris)         3.50-4.67   3.00-3.20   
Bean (Phaseolus vulgaris) leaves         0.00   
Birds (dead poultry)   0.00         
Brewery waste       0.00     
Cassava (Manihot esculenta)     0.90-1.20     1.10-1.25   
Cassava (Manihot esculenta) flour   0.50-0.70   0.60-0.80   0.75-85     0.80-0.85 
Cassava (Manihot esculenta) leaves     0.00       
Coconut (Cocos nucifera) paste       2.05-2.20     
Cocoyam (Caladium spp) leaves     0.00     0.00   0.00 
*Common salt (Sodium chloride)     1.00-1.60     1.20-1.80   
Copra cake    0.80-0.85     0.44-0.48     
Cotton (Gossypium spp) seed cake   0.9-1.0         
Cow (Bos Taurus) blood meal   0.40-0.50   0.40     0.60-0.80   
Fish meal (Rastrinneobola argentea)   1.60-2.60   1.20-3.63   1.30-2.40   1.60-2.40   4.00-5.00 
Groundnut (Arachis hypogaea)     4.00-4.43       3.80-4.42 
Groundnut (Arachis hypogaea) bran   0.10-0.24   0.17-0.40   0.09-0.18     0.10-0.20 
Groundnut (Arachis hypogaea) cake   1.20-1.44     1.00-1.20     
Kitchen wastes       0.00   0.00   
*Lysine   7.00         
Maize (Zea mays)      0.70-1.00   0.54-0.90   0.70-0.90   0.80-0.90   0.80-1.00 
Maize (Zea mays) bran   0.10-0.40   0.27-0.30   0.29-0.50     0.20-0.34 
Maize (Zea mays) gluten/meal     0.53-0.80     0.60-0.90   
*Methionine   13.00         
Millet (Urochloa ramose)         1.22-1.40   
*Supplement/additive 
 
 
 
 
 
 
 
 
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Table 4.1b Checklist of utilized fish feed ingredients in Ashanti, Brong Ahafo, Central, Volta and Western Region of Ghana 
 
 
 
Ingredient 
Region 
Ashanti Brong Ahafo Central Volta Western 
Occurrence Cost per 
Kg 
(GHS) 
Occurrence Cost per 
Kg 
(GHS) 
Occurrence Cost per 
Kg 
(GHS) 
Occurrence Cost per 
Kg 
(GHS) 
Occurrence Cost per 
Kg 
(GHS) 
*Oyster shells    0.14-0.16   0.30-0.40       
Palm fruit fibre         0.60-0.80   
Palm kernel cake     0.01-0.02   0.02-0.08   0.03-0.05   0.01-0.02 
Palm oil (Elaeis quineensis)   3.80-4.40         3.0-3.40 
‘Pito’ mash     0.20-0.30       
Potato (Solanum tuberosum) leaves         0.00   
Poultry offal   0.83-1.25         
*Premix (minerals and vitamins)   6.00   6.00   6.50     6.00 
Rice (Oryza sativa)           4.80-5.50 
Rice (Oryza sativa) bran   0.30-0.44   0.27-0.46   0.26-0.39   0.22-0.36   0.28-0.32 
Soya bean (Glycine max)        2.20   2.90   1.80-1.90 
Soya bean (Glycine max) meal/cake   1.20-1.50   1.60   1.20-1.40     1.00-1.25 
Wheat (Triticum aestivum) bran   0.60-0.65   0.44-0.54   0.44-0.56   0.52-0.60   0.56-0.60 
*Supplement/additive 
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4.2 Commercial Fish Diets Used by Fish Farmers in Ashanti, Brong-Ahafo, Central,  
       Volta and Western Region  
The checklist of the commercial fish diets used by some of the farmers in the five regions 
and the price per kilogramme are presented in Table 4.2. Four main commercial diet 
types were being used in all the five regions surveyed. Raanan was being used in all the 
regions whilst Coppens was being used in Ashanti, Brong Ahafo and Western regions. 
Artemia was being used in the Ashanti and Western regions and Biomar in the Western 
region only. Artemia was not used throughout the rearing period of fish, but it was mainly 
used to feed post larval African catfish, Clarias gariepinus. There were both inter- and 
intra- regional differences in the price per kilogramme of the commercial fish diets. The 
unit cost of a given brand of the diets was determined by its crude protein content. Diets 
with higher crude protein contents cost higher. The cost of any particular commercial diet 
was also influenced by location. The farther the location from the main retailers/dealers, 
the more expensive it was. 
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Table 4.2  Checklist of commonly utilized commercial fish feeds in Ashanti, Brong Ahafo, Central, Volta and Western Regions of Ghana 
Fish Feed Country of 
Origin 
Region 
  Ashanti Brong Ahafo Central Volta Western 
Occurrence 
 
Cost per 
Kg 
(GH¢) 
Occurrence Cost per Kg 
(GH¢) 
Occurrence Cost per 
Kg 
(GH¢) 
Occurrence Cost per 
Kg 
(GH¢) 
Occurrence Cost per 
Kg 
(GH¢) 
Artemia China   150.00         140.00 
Biomar France           3.60-4.00 
Coppens Germany   5.40-6.53   5.67-5.00       5.30-6.60 
Raanan Ghana   3.40-5.75   3.50-6.30   3.30-6.50   3.40-6.30   3.40-6.30 
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4.3 Use of Fish Diets by Fish Farmers in Ashanti, Brong-Ahafo, Central, Volta 
      and Western Region  
The use of fish diets varied widely among the 5 Regions surveyed (Figure 4.1). The 
Region with the highest usage of commercial fish diets among fish farmers was Western 
whilst the least was Ashanti. Of the 38 farmers interviewed in the Western Region, 21 of 
them representing about 55.3 % used only commercial fish diets whilst 3 representing 
about 11.1 % of the 27 farmers in the Ashanti used only commercial fish diets.  On the 
whole, out of the 147 respondents in all the five regions, about 40.4 % used commercial 
fish diets in the Western region alone. There was no exclusive use of commercial fish 
diets among the respondents in the Volta Region. A larger proportion of farmers in the 
Ashanti Region (about 48.2 %) used both commercial and farm-made fish diets than 
farmers in the other Regions surveyed. A larger proportion of farmers in the Ashanti used 
farm-made fish diets than those in the other Regions. Most farmers in the Ashanti Region 
used both the commercial and farm-made diets than farmers in the other four Regions. 
Only in the Volta and Western Regions that some fish farmers did not feed their fish (i.e 
they maintained extensive culture systems). The percentage of this group of farmers was 
significantly higher in the Volta (33.3 %) than in the Western Region (7.9 %).  
 
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Figure 4.1   Percentage of fish diet types used by fish farmers in Ashanti, Brong-Ahafo, Central,  
                    Volta and Western Region  
 
 
 
 
Figure 4.2   Percentage of fish farmers that used the various types of fish diets in Ashanti, Brong-     
                   Ahafo, Central, Volta and Western Region 
 
11.1 
43.2 45 
0 
55.3 
40.7 
36.4 
15 
22.2 
7.9 
48.2 
20.4 
40 
44.5 
28.9 
0 0 0 
33.3 
7.9 
0 
10 
20 
30 
40 
50 
60 
ASHANTI BRONG-AHAFO CENTRAL VOLTA WESTERN 
P
ER
C
EN
TA
G
E 
O
F 
D
IE
T 
TY
P
E 
U
SE
D
 
REGION 
COMMERCIAL FARM-MADE BOTH NO FEED 
37.7 
26.8 
35.5 
COMMERCIAL  
FARM-MADE 
COMMERCIAL & FARM-MADE 
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The results of the survey indicated that out of the 138 fish farmers who used fish diets in 
all the five Regions, 37.7 % used commercial diets, 26.8 % used farm-made diets whilst 
35.5 % used both commercial and farm-made diets (Figure 4.2).  
 
4.4 Use of Commercial Fish Diets by Fish Farmers in Ashanti, Brong-Ahafo,  
      Central, Volta and Western Region  
The survey revealed that of the 102 fish farmers in all the five Regions, who used various 
types of commercial fish diets, majority of these (about 86.2 %) used Raanan, about 9.8 
% used Coppens, about 2.0 % used Biomar and about 2.0 % also used Artemia (Figure 
4.3). 
 
 
Figure 4.3   Percentage of fish farmers using the various types of commercial fish diets in  
                   Ashanti, Brong-Ahafo, Central, Volta and Western Region  
  
 
 
 
86.2 % 
9.8 % 
2 .0 % 2.0 % 
0 
10 
20 
30 
40 
50 
60 
70 
80 
90 
100 
RAANAN COPPENS BIOMAR ARTEMIA 
P
ER
C
EN
TA
G
E 
O
F 
FA
R
M
ER
S 
TYPE OF COMMERCIAL FISH DIETS 
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 4.5 Proximate Compositions of Selected Ingredients 
The proximate compositions of the ingredients (as-fed basis) selected for the formulation 
and preparation of the farm-made fish diets are shown in Table 4.3 below:  
Table 4.3  Proximate compositions (% as-fed), gross energy (kJ g-1), phosphorous (%) and prices  
                  (GHS kg-1) of the selected feed ingredients used in the formulation and preparation of  
                  farm-made diets A (supplemented diet) and B (unsupplemented diet) 
 Cassava flour Fish meal (Tuna) Maize (white) Palm oil Soybean meal Wheat bran 
DM 88.25 ± 0.06 95.21 ± 0.04 88.93 ± 0.02 100.00 ± 0.01 91.54 ± 0.07 87.56 ± 0.08 
 
CP 1.48 ± 0.03 60.20 ± 0.04 9.31 ± 0.02 0.00 ± 0.09 43.25 ± 0.03 18.42 ± 0.07 
 
CL 0.46 ± 0.02 9.74 ± 0.06 3.38 ± 0.06 100.00  ± 0.01 8.55 ± 0.06 4.64 ± 0.06 
 
CF 2.01 ± 0.07 5.73  ± 0.06 2.80 ± 0.03 0.00 ± 0.04 6.36 ± 0.07 9.87 ± 0.06 
 
Ash 2.62 ± 0.01 17.73 ± 0.07 1.39 ± 0.09 0.00 ± 0.05 9.54 ± 0.03 5.71 ± 0.02 
 
NFE 81.68 ± 0.04 1.81 ± 0.06 71.58 ± 0.03 0.00 ± 0.04 23.84 ± 0.04 48.92 ± 0.06 
 
GE 14.54 ± 0.03 18.39 ± 0.09 15.81 ± 0.02 39.54 ± 0.05 17.69 ± 0.04 14.57 ± 0.09 
 
P 0.96 ± 0.07 19.43 ± 0.06 2.19 ± 0.03 7.69 ± 0.04 4.23 ± 0.03 5.99 ± 0.04 
 
Price 1.32 2.30 0.72 3.74 2.40 0.64 
 DM = dry matter, CP = crude protein, CL = crude lipid, CF = crude fibre, NFE = nitrogen free extract,  
 GE = gross energy, P = phosphorus 
 
The results of the proximate compositions of the ingredients showed that fish meal had 
the highest crude protein (60.20 %) whilst Cassava flour had the least (1.48 %). The gross 
energy for the ingredients ranged from 14.54 to 39.54 kJ g-1, with Palm oil containing the 
highest (39.54 kJ g-1). Fish meal had the highest amount of Phosphorus (19.43 %) whilst 
Cassava flour had the least (0.96 %).  Crude lipid content of Palm oil was the highest 
(100.0 %). The ingredient with the highest Crude fibre content was Wheat bran (9.87 %) 
and Fish meal had the highest Ash (17.73 %) content. Palm oil was the most expensive 
(3.74 GHS kg-1) whilst Wheat bran was the least expensive (0.64 GHS kg-1).  
                                                                                                                                       
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4.6 Proximate Compositions of Study Diets 
The proximate compositions of diets A (farm-made diet supplemented with lysine, 
methionine, and vitamin-mineral premix), B (farm-made diet with no supplements), C 
(Coppens), D (Raanan) and E (a 1:1 mixture of diets B and D) are shown in Table 4.4 
below: 
 
Table 4.4  Proximate composition (% as-fed), gross energy (kJ g-1), phosphorous (g kg-1),  
                 Chromic oxide concentrations and prices (GHS kg-1) of Diets A, B, C (Coppens),  
                 D (Raanan) and E 
           A          B    Coppens       Raanan           E 
DM 
 
89.60 ± 0.03 90.59 ± 0.02 96.58 ± 0.04 90.40 ± 0.02 89.66 ± 0.06 
CP 
 
31.29 ± 0.05 31.53 ± 0.04 34.58 ± 0.01 31.21 ± 0.07 33.80 ± 0.03 
CL 
 
10.36 ± 0.01 12.39 ± 0.03 6.94 ± 0.05 4.78 ± 0.06 10.00 ± 0.07 
CF 
 
5.21 ± 0.04 4.46 ± 0.02 4.48 ± 0.06 3.91 ± 0.06 4.01 ± 0.08 
Ash 
 
8.80 ± 0.09 8.39 ± 0.04 5.16 ± 0.01 9.45 ± 0.02 8.02 ± 0.05 
NFE 
 
33.94 ± 0.02 33.82 ± 0.07 45.42 ± 0.06 41.05 ± 0.08 33.83 ± 0.09 
GE 
 
17.31 ± 0.05 18.15 ± 0.04 18.70 ± 0.05 16.31 ± 0.03 17.75 ± 0.05 
P 
 
11.07 ± 0.06 12.80 ± 0.02 6.56 ± 0.04 8.54 ± 0.08 7.54 ± 0.04 
Cr2O3 
 
0.42 ± 0.02 0.41 ± 0.03 0.41 ± 0.01 0.42 ± 0.02 0.40 ± 0.05 
Price 1.88 1.75 5.00 3.25 2.32 
DM = dry matter, CP = crude protein, CL = crude lipid, CF = crude fibre, NFE = nitrogen free 
extract, GE = gross energy, P = phosphorus, GHS = Ghana cedis 
  
Proximate analyses of the diets showed that Coppens had the least moisture content. 
Raanan had the least (31.21 %) crude protein content whilst Coppens had the highest 
(34.58 %). The analysed crude protein levels of Coppens and Raanan were higher than 
levels (34.00 % and 30.00 % respectively) declared by the manufacturers as indicated on 
the labels of their respective feed bags. Results of the analyses also showed that values 
(31.29 % and 31.53 % respectively) obtained for the crude protein contents were higher 
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for the formulated diets (A and B) than the calculated value (30.00 % for each diet). Diet 
E had higher (33.80 %) crude protein content than any of its constituent diets (B and 
Raanan). For crude lipid, values (6.94 % and 4.78 %) obtained for Raanan and Coppens 
respectively, were lower than those for the formulated diets (10.36 % and 12.39 % for A 
and B respectively). The value for Coppens was about two times lower than what the 
producer declared. The gross energy of the diets ranged from 16.31 to18.70 kJ g-1 with 
Raanan having the least and Coppens the highest. Values obtained for the analyses of 
Ash ranged from 5.16 to 9.45 %. Coppens had the least whist Raanan had the highest. 
Crude fibre contents of the diets ranged from 3.91 to 5.21 % with Raanan having the least 
and farm-made diet A the highest. The chromic oxide concentrations in the diets ranged 
from 0.40 to 0.42 %. The unit cost of the diets ranged from 1.75 to GHS 5.00 with the 
commercial ones being more expensive than the farm-made ones. The most expensive 
diet was Coppens (5.00 GHS kg-1) whilst the least was farm-made diet B (1.75 GHS kg-
1).   
 
The comparison between the calculated/declared crude proteins and the analysed crude 
proteins of the various diets is shown in Table 4.5. The mean deviation was 3.78 ± 1.46 
with farm-made diet A showing the highest (4.3 %) deviation whilst Coppens showed the 
least (1.7 %).  
 
 
 
 
 
 
 
 
 
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Table 4.5  Percentage deviation of the observed from the expected crude proteins of the various  
                 diets  
Diet  Calculated/Declared CP  Analysed CP Deviation (%) 
A 30.00 31.29 4.3 
B 30.00 31.53 5.1 
Coppens 34.00 34.58 1.7 
Raanan 30.00 31.21 4.0 
 
 
4.7 Experimental Fish   
The hand-sexing of the nursed experimental fish was possible when they attained sizes 
ranging between 19.00 and 29.00. In all, about 93 % of the population with weights 
ranged 19.2 to 28.7 g was found to be males. Their mean living weight (±SD) was 22.8 ± 
2.1 g and mean SL (±SD) was 8.9 ± 0.3 cm. There were no significant differences 
(ANOVA, p > 0.05) among treatments.  
 
4.8 Growth Performance of Cultured Fish 
The overall values of growth performance of O. niloticus fed the various farm-made and 
commercial diets for twenty weeks is presented as mean living weight (±SD) (Appendix 
III) and illustrated graphically in Figure 4.4. After the second week of culture, growth 
was rapid in all the treatments up to the sixth week. Growth was generally slow between 
the sixth and eighth week. However, growth peaked after the eighth week in all the 
treatments, but highest in fish fed Raanan till the eighteenth week. The highest final mean 
weight of 187.6 g occurred in fish fed Raanan whilst the least final mean weight of 131.0 
g occurred in fish fed farm-made diet B. There was significant difference (Tukey’s MRT, 
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p < 0.05) in final mean weight between the fish fed Raanan and those fed the other diets. 
There was no significant difference (ANOVA, p > 0.05) between the final mean weights 
of fish fed Coppens and those fed farm-made diet A. 
 
Fish fed Raanan had the highest weight gain (165.0 g) followed by those fed Coppens 
(125.8 g) and the least (108.2 g) were those fed diet B (Figure 4.5). The percentage 
weight gain and specific growth rate were highest for fish fed Raanan (728.8 % and 1.63 
% day-1 respectively) and least for those fed diet B (466.2 % and 1.33 % day-1 
respectively) (Table 4.6). However, there was no significant difference in specific growth 
rate among dietary treatments. The values for mean daily weight gain ranged from 0.77 to 
1.18 g fish-1. Fish fed Raanan had the highest daily weight gain whilst those fed farm-
made diet B had the least. There were no significant differences among dietary treatments 
except between fish fed Raanan and diet B.  Total fish yield (TFY) ranged from 0.25 to 
0.38 kg m-2 whilst net fish yield (NFY) ranged from 0.20 to 0.33 kg m-2. Both TFY and 
NFY were significantly higher in O. niloticus fed Raanan whilst there were no significant 
differences among the other dietary treatments. Survival ranged from 86.67 to 100.00 %. 
The highest survival was observed in fish fed Raanan whilst the least occurred in fish fed 
Coppens. However, there were no significant differences among dietary treatments. 
Condition factor of fish fed the various diets ranged from 2.0 to 3.2. There was no 
significant difference (ANOVA, p > 0.05) in condition factor among dietary treatments 
except Raanan that was significantly lower (Tukey’s MRT, p < 0.05). 
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Figure 4.4  Growth performance of Oreochromis  niloticus fed commercial and farm-made fish 
                   diets for twenty weeks 
 
 
 
Figure 4.5  Weight gain by  Oreochromis niloticus fed commercial and farm-made fish diets for 
                   20 weeks. Bars with different letters are significantly different  
                   (Tukey’s MRT,  p < 0.05)   
0 
20 
40 
60 
80 
100 
120 
140 
160 
180 
200 
0 2 4 6 8 10 12 14 16 18 20 
M
EA
N
 B
O
D
Y
 W
EI
G
H
T 
(g
) 
WEEKS 
Diet A Diet B Coppens Raanan Diet E 
117.3 ab 
107.8 a 
125.6 b 
165.0 c 
118.2 b 
0 
20 
40 
60 
80 
100 
120 
140 
160 
180 
Diet A Diet B Coppens Raanan Diet E 
M
EA
N
 W
EI
G
H
T 
G
A
IN
 (
g)
 
DIET TYPE 
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Figure 4.6   Percentage final wet weight distributions of Oreochromis niloticus in each dietary  
                   treatment after 20 weeks of feeding 
 
At the end of the growth trials, only O. niloticus fed Raanan recorded a size range 300-
400 g, and this constituted about 1.67 % of the fish fed Raanan (Figure 4.6). Besides, fish 
fed Raanan recorded the greatest proportion of the size range 150-299 g (80.00 %), 
followed by fish fed Coppens (48.08 %) whilst the least (15.79 %) of this size group was 
observed in fish fed farm-made diet B. The highest number (84.21 %) of O. niloticus of 
size below 150.0 g occurred in those fed farm-made diet B, followed by fish fed farm-
made diet A whilst the least (18.33 %) was recorded in those fed Raanan.  
67.24 
84.21 
48.08 
18.33 
62.96 
32.76 
15.79 
51.92 
80 
37.04 
0 0 0 1.67 0 
0 
10 
20 
30 
40 
50 
60 
70 
80 
90 
Diet A Diet B Coppens Raanan Diet E 
P
ER
C
EN
TA
G
E 
DIET TYPE 
< 150.0 g 
150-299 g 
300-400 g 
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Table 4. 6 Mean growth performance of the cultured Nile tilapia fed diets A, B, Coppens, Raanan and E for 20 weeks  
Parameter Diet 
A B Coppens Raanan E 
Initial Weight (g) 23.0 ± 2.0a   23.2 ± 1.9a 22.7 ± 1.9a 22.6 ± 2.3a 22.5 ± 2.2a 
Final Weight (g) 140.3 ± 23.4ab 131.0 ± 24.4a 148.3 ± 25.4b 187.6 ± 42.1c 140.7 ± 28.5b 
Initial Standard Length (cm)  89.5 ± 2.9a 89.1 ± 2.5a  88.3 ± 2.6a 88.4 ± 2.6a 88.1 ± 3.2a 
Final Standard length (cm) 162.6 ± 8.9ab 159.9 ± 9.2a 165.3 ± 8.7b 177.6 ± 13.7c 163.6 ± 11.2b 
Weight Gain (%) 511.0 ± 50.5ab 466.2 ± 38.8a 555.3 ± 29.0b 728.8 ± 45.0c 526.6 ± 36.6b 
Specific Growth Rate (% day-1) 1.39 ± 0.07a  1.33 ± 0.05a 1.45 ± 0.03a 1.63 ± 0.04a 1.41 ± 0.05a 
Daily Weight Gain (g/fish) 0.84 ± 0.06a 0.77 ± 0.07a 0.90 ± 0.08a 1.18 ± 0.19b 0.84 ± 0.06a 
Survival (%) 96.7 ± 2.89a 95.0 ± 8.66a  86.67 ± 5.77a 100.0 ± 0.00a 90.0 ± 10.00a  
Total Fish Yield (Kg m-2) 0.27 ± 0.24a 0.25 ± 0.18a 0.26 ± 0.15a 0.38 ± 0.23b 0.25 ± 0.19a 
Net Fish Yield (Kg m-2)  0.23 ± 0.24a 0.20 ± 0.17a 0.21 ± 0.16a 0.33 ± 0.23b 0.21 ± 0.17a 
Condition Factor 3.3 ± 0.09a 3.2 ± 0.12a 3.3 ± 0.08a 2.0 ± 0.07b 3.2 ± 0.09a 
Values are means ±SD of three replicates. Means within the same row with different letters are significantly different (p < 0.05). 
 
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4.9 Feed and Nutrient Efficiency of Cultured Fish 
The data on feed and nutrient efficiency of the cultured fish is shown in Table 4.7 above. 
The FCR values ranged from 2.35 to 3.26 at the end of the growth study. FCRs of all the 
dietary treatments were not significantly different (ANOVA, p > 0.05) except diets B and 
Raanan that were significantly different (Tukey’s MRT, p < 0.05) from each other with 
the latter being higher. Raanan was the most efficient as it gave the least FCR of 2.35 
whilst diet B was the least efficient, with the highest FCR of 3.26. Feed efficiency was 
less than 50.0 % in all the dietary treatments and the values ranged from 30.10 % in diet 
B to 43.03 % in Raanan. Raanan was significantly higher than diets A, B, Coppens and E. 
Feed intake ranged from 344.83 to 388.11 g and there were no significant differences 
among all the diets. There was no significant difference in protein utilization efficiency 
among all the diets and the values ranged from 1.18 to 1.67. The protein productive value 
was significantly higher (Tukey’s MRT, p < 0.05) in fish fed Raanan and there were no 
significant differences among fish fed diets B, Coppens and E. The percentage energy 
retention ranged from 8.32 to 15.32 %, with fish fed Raanan being significantly higher 
whilst those fed Coppens being lower.   
 
 
 
 
 
 
 
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Table 4.7 Feed and nutrient efficiency of the cultured Nile tilapia fed diets A, B, Coppens, Raanan and E for 20 weeks  
Parameter Diet 
A B Coppens Raanan E 
Feed Conversion Ratio  2.96 ± 0.19b 3.26 ± 0.21ab 2.92 ± 0.12b 2.35 ± 0.13bc 2.92 ± 0.07b 
Feed Efficiency (%) 34.02 ± 2.01a 30.10 ± 2.10a 33.00 ± 1.11a  43.03 ± 2.00b 34.04 ± 1.21a  
Feed Intake (g) 347.10 ± 13.28a   351.32  ± 12.87a 366.76  ± 14.31a 388.11  ± 18.92a 344.83  ± 13.63a 
Protein Efficiency Ratio 1.37 ± 0.84a 1.27 ± 0.88a  1.18 ± 0.64a 1.67 ± 0.77a 1.34 ± .76a 
 Protein Productive Value (%) 24.89 ± 0.13a 20.44 ± 0.34b 21.15 ± 0.18b 28.80 ± 0.03c 22.07 ± 0.21b 
Energy Retention (%) 11.96 ± 0.29a 10.30 ± 0.20b 8.32 ± 0.18c 15.32 ± 0.14d 10.78 ± 0.31b 
Values are means ±SD of three replicates. Means within the same row with different letters are significantly different (p < 0.05). 
 
 
 
 
 
 
 
 
 
 
 
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4.10 Length-Weight Relationship by Diet Type 
The linear least square regression of log weight (body weight, W) on log standard length 
(SL) (i.e. log W = b log SL + log a) computed for diets A, B, Coppens, Raanan and E are 
shown in Figures 4.7 to 4.11 below: 
 
 
     Figure 4.7 Length-weight relationship of Oreochromis niloticus fed farm-made diet A 
 
 
 
 
 
 
 
 
Log W = 2.9806 Log L  - 4.4382 
R² = 0.9958 
N = 58 
0 
0.5 
1 
1.5 
2 
2.5 
1.9 1.95 2 2.05 2.1 2.15 2.2 2.25 
Lo
g 
W
 
Log SL  
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        Figure 4.8 Length-weight relationship of Oreochromis niloticus fed farm-made diet B 
 
 
        Figure 4.9 Length-weight relationship of Oreochromis niloticus fed Coppens 
 
 
Log W = 3.0254 Log L - 4.5245 
R² = 0.9983 
N = 57 
0 
0.5 
1 
1.5 
2 
2.5 
1.9 1.95 2 2.05 2.1 2.15 2.2 2.25 
LO
g 
W
 
Log SL 
Log W = 3.0307 Log L - 4.5423 
R² = 0.9972 
N = 52 
0 
0.5 
1 
1.5 
2 
2.5 
1.9 1.95 2 2.05 2.1 2.15 2.2 2.25 
Lo
g 
W
 
Log SL 
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            Figure 4.10 Length-weight relationship of Oreochromis niloticus fed Raanan 
 
 
           Figure 4.11 Length-weight relationship of Oreochromis niloticus fed diet E 
 
 
Log W = 3.0923 Log L - 4.6601 
R² = 0.9963 
N = 60 
0 
0.5 
1 
1.5 
2 
2.5 
1.9 1.95 2 2.05 2.1 2.15 2.2 2.25 2.3 
Lo
g 
W
 
Log SL 
Log W = 3.0039 Log L - 4.4873 
R² = 0.997 
N = 54  
0 
0.5 
1 
1.5 
2 
2.5 
1.9 1.95 2 2.05 2.1 2.15 2.2 2.25 
Lo
g 
W
 
Log SL  
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The regression equations computed from data for each dietary treatment are as follows: 
Farm-made diet A: W = 0.0000365 SL2.9806  (R2 = 0.996) 
Farm-made diet B: W = 0.0000299 SL3.0254  (R2 = 0.998) 
              Coppens: W = 0.0000287 SL3.0307 (R2 = 0.997) 
                Raanan: W = 0.0000219 SL3.0923 (R2 = 0.996) 
            (Farm-made + Raanan), diet E: W = 0.0000326 SL3.0039 (R2 = 0.997) 
 
The above equations clearly indicated that the various dietary treatments exhibited 
differences in the value of exponent b. The weight gain was almost the same 
(approximately 3) in O. niloticus fed both the farm-made and commercial diets.  
 
Table 4.8 Equation parameters of Length-weight and condition factors for Oreochromis niloticus  
                 fed the various diet type 
Treatment B R2 K 
 A 3.0 0.996 3.3 
B 3.0 0.998 3.2 
Coppens 3.0 0.997 3.3 
Raanan 3.1 0.996 2.0 
E 3.0 0.997 3.2 
b = slope of regression line, R = coefficient of regression, K = condition factor 
 
The values of K for dietary treatments A and Coppens were equal and the highest (3.3) 
whilst the K-value for Raanan was the least (2.0) (Table 4.8).  
 
4.11 Health Status of O. niloticus according to Diet Type 
There were no abnormalities observed in the eyes, fins, gills, guts, kidneys, livers, 
pseudobranchs, opercles or spleens in any of the fish fed the various diets. Abdominal fat 
covered less than half of the viscera in almost all the fish examined in the various dietary 
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treatments and the values ranged from 0.33 to 1.13. Generally, the least gut fat content 
was observed in the fish fed diet E. The highest gut fat content occurred in O. niloticus 
fed Coppens. However, there were no significant differences (ANOVA, p > 0.05) among 
dietary treatments, except diet E that was significantly lower (Tukey’s MRT, p < 0.05). 
Patches of red-brown colouration were observed on the scales of about 12 % of fish fed 
Coppens. However, these were superficial. 
  
4.12 Body Composition of Cultured O. niloticus 
The whole-body proximate compositions of O. niloticus at the commencement and end of 
the growth study are presented in Table 4.9. The results showed that there was no 
significant difference (ANOVA, p > 0.05) in whole-body moisture contents among all the 
dietary treatments and the values ranged from 75.20 to 76.26 %, and all were lower than 
the initial whole-body moisture composition of the experimental fish. The crude protein 
contents ranged from 16.20 to 18.46 % and that of fish fed farm-made diet A was 
significantly higher (Tukey’s MRT, p < 0.05) than those fed the other diets and the 
values observed in all the dietary treatments were higher than that of the initial content of 
the experimental fish.  The crude lipid contents of O. niloticus fed farm-made diet B and 
Coppens were significantly higher than those fed the other diets and the values ranged 
from 3.04 to 4.20 %. The nitrogen free extracts (carbohydrates) content of fish fed diet E 
was significantly higher and the values for the dietary treatments ranged from 0.68 to 
2.53 %. The crude fibre content of O. niloticus fed diet A was significantly higher than 
the other dietary treatments and all the values (0.07 to 0.23 %) observed were lower than 
that of the experimental fish at the commencement of the growth trials. The Ash and 
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Phosphorus contents of O. niloticus fed Coppens were significantly lower than those fed 
the other diets, and the values ranged from 1.33 to 1.96 % and 16.71 to 21.57 % 
respectively. The ash contents of O. niloticus in all the dietary treatments were higher 
than that of the fish before the commencement of the growth trials. The gross energy 
contents of all the fish at the end of the study ranged from 5.47 to 5.95 kJ g-1 and that of 
fish fed Coppens was significantly higher. The values recorded in all the dietary 
treatments were higher than that of the initial whole-body content of the experimental 
fish. The values of hepatosomatic index of the various dietary treatments ranged from 
1.41 to 2.17 and O. niloticus fed Coppens was significantly higher than those fed the 
other diets whilst those fed farm diet B was significantly lower.   
 
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Table 4.9 Whole body proximate composition (%) gross energy (kJ g-1) and hepatosomatic index of cultured Nile tilapia (mean ± SD)  
Constituent  Initial A B Coppens Raanan E 
MC 81.21 ± 0.16 75.20  ± 0.53a 75.61 ± 1.06a  75.89 ± 0.19a 75.65 ± 0.60a 76.26 ± 0.23a 
CP 12.49 ± 0.42    18.46 ± 1.04a 16.37 ± 5.18b 17.76 ± 2.19c 17.87 ± 2.96c 16.20 ± 4.63b 
CL 3.51 ± 0.06 3.53 ± 0.55b 4.20 ± 0.37a 4.13 ± 0.67a 3.14 ± 0.40b 3.04 ± 0.59b 
NFE 0.94 ± 0.63 0.68 ± 1.22c 1.73 ± 5.22bcd 0.71 ± 1.70a 1.42 ± 2.94c 2.53 ± 4.33cde 
CF 1.10 ± 0.13   0.23 ± 0.04a  0.13 ± 0.05b 0.18 ± 0.01c 0.07 ± 0.01d 0.07 ± 0.01d 
Ash 0.75 ± 0.36 1.90  ± 0.18cd 1.96 ± 0.26cd 1.33 ± 0.20a 1.85 ± 0.28cde 1.90 ± 0.28bcd 
P 16.85 ± 119.24 21.37 ± 11.98c 21.57 ± 8.37cd 16.71 ± 7.27a 18.75 ± 7.74b 21.25 ± 7.42c 
GE 4.50 ± 0.03 5.88 ± 0.21c   5.83 ± 0.31cde   5.95 ± 0.13a       5.71 ± 0.12c   5.47 ± 0.21bc   
HIS  1.62 ± 0.46bc  1.41 ± 0.40abc 2.17 ± 0.73cd 1.71 ± 0.34bc 1.81 ± 0.53c 
MC = moisture content, CP = crude protein, CL = crude lipid, NFE = nitrogen free extracts, CF = crude fibre, P = phosphorus, GE = gross energy,  
HSI = hepatosomatic index. Values are means ± SD of three replicates. Values within the same row with dissimilar letters are significantly different (Tukey’s 
MRT, p < 0.05). 
 
 
 
 
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4.13 Cost Effectiveness of the Diets 
The costs per kilogramme of the commercial diets were higher compared to the farm-
made ones (Table 4.10). Coppens was the most expensive (GHS 5.00 kg-1) and the least 
(GHS 1.93 kg-1) was farm-made diet B. The cost analyses showed that it was more 
expensive (GHS 12.35) to use Coppens to produce a kilogramme of tilapia than any of 
the other diets whilst the farm-made diet A cost least (GHS 5.12). The highest profit was 
made by the use of farm-made diet A, followed by farm-made diet B whilst the least was 
made by the use of Coppens. The results of this study also revealed that it was more 
profitable to use farm-made diet B alone than mixing it in equal proportions with Raanan. 
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Table 4.10 Cost effectiveness of diets fed to Nile tilapia  
Diets Cost per kg of 
feed (GHS) 
Feed input 
(kg) 
Cost of feed used 
(GHS) 
Harvested biomass 
(kg) 
Estimated value of 
biomass (GHS)** 
Incidence Cost 
(GHS/kg) 
Profit Index 
A* 2.07 20.12 41.65 8.14 52.03 5.12 1.25 
B* 1.93 19.93 38.46 7.46 47.00 5.16 1.22 
Coppens 5.00 19.05 95.25 7.71 50.07 12.35 0.53 
Raanan 3.25 23.29 75.69 11.26 75.04 6.72 0.99 
E 2.59 18.59 48.15 7.60 48.83 6.34 1.01 
*Cost per kg of feed include labour, constituting 10 % of the cost of producing the feed, **Sale of fish: < 150 g = GHS 6.20, 150-299 g = GHS 6.70,  
300-400 g = GHS 7.50 
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4.14 Water Quality 
The detailed value range of water quality parameters in hapas for the various dietary 
treatments and the open pond water during the growth trials are shown in Appendix IV 
whilst the summary of statistical result range (maximum and minimum), mean and 
standard deviation values are shown in Table 4.11. Generally, all water quality 
parameters were within the suitable range for Nile tilapia (Nabil and Gamal, 2010; 
Swann, 2007; Hussain, 2004; Suresh, 2003; Popma and Masser, 1999; Stickney, 1979).  
Table 4.11  Summary of statistical analysis of water quality parameters for the various dietary  
                    treatments and the open pond water for a period of 140 days 
Parameter Maximum Minimum Mean Standard Deviation 
Temperature (0C) 29.83 27.58 28.90 0.02 
Dissolved Oxygen 3.30 1.15 2.16 0.15 
Salinity (ppt) 0.04 0.03 0.04 0.00 
Conductivity (μS cm-1) 100 61 86 2 
pH 7.62 5.79 6.39 0.05 
Phosphate (mg L-1) 2.55 0.10 0.29 0.11 
Nitrate (mg L-1) 6.60 0.40 1.28 0.21 
Nitrite (mg L-1) 0.113 0.001 0.008 0.003 
Ammonia (mg L-1) 0.52 0.07 0.35 0.01 
Alkalinity (mg L-1) 73.0 52.0 61.0 0.8 
Total Suspended Solids (ppt) 85 18 39 3 
Total hardness (mg L-1) 4.98 2.05 3.55 0.10 
 
During the experimental period, the temperatures recorded varied in the range 27.58-
29.83 0C in the various dietary treatments and the open pond water (Table 4.11). Both 
temporal and spatial fluctuations in temperature were observed in all the treatments. The 
highest maximum value (29.83 0C) was recorded in dietary treatment A whilst the least 
minimum value (27.58 0C) was observed in treatment E. There were no significant 
differences (ANOVA, p > 0.05) among the mean values of all the treatments. 
 
The dissolved oxygen (DO) recorded in all the treatments and the open pond waters 
during the study varied in the range 1.15-3.30 mg L-1. Both temporal and spatial 
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fluctuations in DO were observed in all the treatments. Both the highest maximum value 
(3.30 mg L-1) and least minimum value (1.15 mg L-1) were recorded in dietary treatment 
A. There were no significant differences (ANOVA, p > 0.05) among the mean values of 
all the treatments. 
 
The recorded salinity in all the treatments and the open pond waters during the study 
were 0.03 and 0.04 ppt. Both the maximum value (0.04 ppt) and the minimum value 
(0.03 ppt) were the same in all the treatments during the study period. All the treatments 
and the open pond waters recorded the same mean value (0.04 ppt). The values of 
conductivity recorded in all the treatments and the open pond waters varied in the range 
100-61 μS cm-1. There were both temporal and spatial variations in conductivity values. 
The highest maximum value (100 μS cm-1) occurred in the open pond waters whilst the 
least minimum value (61 μS cm-1) was recorded in dietary treatment E. There were no 
significant differences (ANOVA, p > 0.05) among the mean values of all the treatments. 
 
The pH-values in all the treatments and the open pond waters were similar. The values 
varied in the range 5.79-7.62. There were slight temporal and spatial variations, but there 
were no significant differences among them. Both the highest maximum pH-value (7.62) 
and least minimum value (5.79) were recorded in dietary treatment A. There were no 
significant differences (ANOVA, p > 0.05) among the mean values of all the treatments. 
 
The phosphate values varied in the range 0.10-2.55 mg L-1. There were both spatial and 
temporal variations in all the treatments and the open pond waters during the study 
period. The highest maximum value (2.55 mg L-1) was recorded in dietary treatment B 
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and the least minimum value (0.10 mg L-1) was in Coppens. Values recorded in dietary 
treatment B were significantly higher (Tukey’s MRT, p < 0.05). 
 
The nitrate values varied in the range 0.40-6.60 mg L-1. There were both spatial and 
temporal variations in all the treatments and the open pond waters during the study 
period. The highest maximum nitrate value (6.60 mg L-1) was recorded in Raanan dietary 
treatment and the least minimum value (0.40 mg L-1) was observed in all the dietary 
treatments except in E and the open pond waters that recorded higher values (0.60 and 
0.50 mg L-1 respectively). Values recorded in the open pond waters were significantly 
lower (ANOVA, p > 0.05). 
 
The nitrite values recorded during this study varied in the range 0.001-0.113 mg L-1. 
There were both spatial and temporal variations in all the treatments and the open pond 
waters during the study period. The highest maximum nitrite value (0.113 mg L-1) was 
recorded in Raanan dietary treatment and the least minimum value (0.001 mg L-1) was 
observed in all the dietary treatments except in E and the open pond waters that recorded 
0.002 and 0.003 mg L-1 respectively. Values recorded in diet A, Coppens and Raanan 
dietary treatments were significantly higher (Tukey’s MRT, p < 0.05). 
  
The ammonia values varied in the range 0.07-0.52 mg L-1. There were both spatial and 
temporal variations in all the treatments and the open pond waters during the study 
period. The highest maximum ammonia value (0.52 mg L-1) was recorded in Coppens 
dietary treatment and the least minimum value (0.07 mg L-1) was observed in dietary 
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treatment E. There was no significant variation between values recorded in the open pond 
waters and the various dietary treatments.    
 
The alkalinity values varied in the range 52.0-73.0 mg L-1. There were both spatial and 
temporal variations in all the treatments and the open pond waters during the study 
period. The highest maximum alkalinity value (73.0 mg L-1) was recorded in Coppens 
dietary treatment and the least minimum value (52.0 mg L-1) was observed in dietary 
treatment E. There was no significant variation between alkalinity values recorded in the 
open pond waters and the various dietary treatments.   
 
The total suspended solids (TSS) values varied in the range 18-85 ppt. There were both 
spatial and temporal variations in all the treatments and the open pond waters during the 
study period. The highest maximum TSS value (85 ppt) was recorded in the open pond 
waters and the least minimum value (18 ppt) was observed in dietary treatment E. TSS 
values recorded in the open pond waters were significantly higher (Tukey’s MRT, p < 
0.05) than that of the various dietary treatments.   
 
The total hardness (TH) values varied in the range 2.05-4.98 mg L-1. There were both 
spatial and temporal variations in all the treatments and the open pond waters during the 
study period. The highest maximum TH value (4.98 mg L-1) was recorded in Coppens 
dietary treatment and the least minimum value (2.05 mg L-1) was observed in dietary 
treatment E. TH values recorded in dietary treatment A was significantly lower than the 
pond waters and the other dietary treatments.  
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4.15 Apparent Digestibility Coefficients of Nutrients in the Diets 
The proximate compositions of the faecal samples of O. niloticus fed the farm-made and 
commercial diets are shown in Table 4.12 below. There was a general reduction in all the 
parameters except the Ash as compared to those of the diets.  
Table 4.12 Proximate composition (%) of faecal samples of Oreochromis niloticus fed the various 
                   diets 
Parameter A B Coppens Raanan E 
Dry matter 67.59 68.98 65.72 71.11 66.48 
Crude protein 21.22 17.80 20.13 13.79 20.56 
Crude lipid 2.12 2.33 2.64 2.51 2.95 
Nitrogen free extract  27.62 32.47 28.63 40.38 27.46 
Crude fibre 3.39 3.37 3.38 2.95 3.03 
Ash 12.70 13.01 10.94 11.48 12.48 
Gross energy 10.60 10.70 10.71 11.18 10.74 
Phosphorus 0.76 0.76 1.24 1.09 1.37 
Chromic oxide 1.41 1.14 1.84 1.19 1.08 
 
The apparent digestibility coefficients (ADCs) of the nutrients and other components in 
the various diets fed to O. niloticus are shown in Table 4.13. There were significant 
differences (Tukey’s MRT, p < 0.05) in the ADCs of all the parameters in all the dietary 
treatments. The ADCs of protein, lipid and phosphorus were similar for farm-made diets 
A and B. On the whole, the ADCs of all parameters for farm-made diet A were higher 
than those of B. The ADCs of lipid and phosphorus for the farm-made diets were higher 
than those of the commercial diets. The digestibility of protein was significantly higher in 
the commercial diets than in the farm-made diets. Digestibility of crude fibre in all the 
diets except in Coppens was higher than carbohydrate. Generally, ADCs of the nutrients 
were highest for Coppens followed by farm-made diet A whilst the least ADCs were 
observed in diet E. (i.e. a 1:1 mixture of farm-made diet B and Raanan). ADC of Ash was 
the least of ADCs of all the other parameters in all the dietary treatments.    
 
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Table 4.13  Apparent digestibility coefficients (%) of dry matter, crude protein, crude lipid,  
                   nitrogen free extract, crude fibre, ash, gross energy and phosphorus in the various  
                   diets fed to Oreochromis niloticus 
Parameter A B Coppens Raanan E 
Dry matter 70.23 ± 0.47a 64.20 ± 0.50b 77.70 ± 0.50c 64.53 ± 0.58b 63.10 ± 0.66b 
Crude protein 79.79 ± 0.30a 79.68 ± 0.28a 87.02 ± 0.31b 84.40 ± 0.30c 77.49 ± 0.29d 
Crude lipid 93.90 ± 0.29a 93.23 ± 0.41a 91.52 ± 0.50a 81.46 ± 0.13b 89.09 ± 0.86a 
Nitrogen free extract  75.75 ± 0.03a 65.44 ± 0.02b 85.94 ± 0.02c 65.28 ± 0.05b 69.97 ± 0.04d 
Crude fibre 77.52 ± 0.01a 72.80 ± 0.04b  83.18 ± 0.06c 73.37 ± 0.02b 72.04 ± 0.04b 
Ash 56.94 ± 0.05a 44.23 ± 0.06b 52.70 ± 0.02c  57.10 ± 0.02d 42.40 ± 0.02e 
Gross energy 81.75 ± 0.42a 78.78 ± 0.18b 87.23 ± 0.37c  75.80 ± 0.53d 77.61± 0.27b  
Phosphorus 97.95 ± 0.03a 97.86 ± 0.04a 95.78 ± 0.17b 95.49 ± 0.26b 93.28 ± 0.16c 
Values within the same row with dissimilar letters are significantly different (Tukey’s MRT, p < 0.05).
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CHAPTER 5.0 DISCUSSION 
5.1 Use of Fish Feed Ingredients   
Both feed ingredients and supplements/additives were being used by small-scale pond 
fish farmers in all the regions (Ashanti, Brong Ahafo, Central, Volta and Western) 
surveyed to produce fish diets. Since Ghana is mainly an agro-based country, the 
ingredients surveyed in the present study were mainly agricultural crops and by-products 
and most were available in most parts of the country and throughout the year. Some of 
the ingredients used by fish farmers as fish feed or in fish diet production were cultivated 
by the farmers themselves as most of them practised integrated culture system.  
 
Of the 32 ingredients and 5 feed supplements/additives surveyed, most of them were 
being utilized in at least three of the regions, whilst some were more localised. This was 
also reflected in the cost per kilogramme of the various ingredients, in that within regions 
where particular ingredients were localised, such ingredients were cheaper than regions 
where they were least available. This suggests that it would be cheaper to produce a 
kilogramme of fish diet in a region where the ingredients used are localised and less 
expensive than in others where such ingredients are not readily available and hence could 
be more expensive.  
 
Availability and price are key determinants for an ingredient to be used. For availability, 
volume, time of availability, (e.g. is it available every day or week or is it only available 
during one season each year), source (e.g. is it available everywhere or only in a 
particular city or region) and accessibility (i.e. supply chain mechanism) are all important 
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determinants (Glencross et al, 2007). Ingredient pricing is obviously critical, and factors 
that drive price change have to be considered. Weather (especially droughts) affects 
supply and price of grains and other agricultural products as in the changing pattern for 
the demand of ingredients for other purposes.  
 
In the present survey, the costs of fish meal were generally high in all the 5 regions. This 
is consistent with observations made by Munguti et al. (2012) that the costs of feed 
ingredients of animal origin were generally high and unlikely to be economically viable 
for semi-intensive culture of O. niloticus and C. gariepinus when their percentage 
inclusion in the diet formulations is over 25 %.  Although most of the ingredients have a 
high potential for inclusion in fish diets due to their nutritional compositions and lack of 
competition as human food, they may still suffer the limitation of competition as such 
ingredients are utilized in poultry and livestock feed producing industries.  
 
During the survey, ingredients such as bean (Phaseolus vulgaris) husks and leaves, dead 
poultry, brewery waste, cassava (Manihot esculenta) leaves, kitchen wastes and potato 
(Solanum tuberosum) leaves were sourced by fish farmers at no cost. These ingredients 
would attract cost and may become unaffordable when their demand and use in farm-
made fish diets increase. The inter- and intra- regional differences in the unit costs of 
most of the ingredients used suggests that there will be remarkable differences in the cost 
of a kilogramme of farm-made fish diet production from region to region using the same 
ingredients. Hence, it will be more profitable to produce and use farm-made fish diets in 
some regions than others using the same ingredients. Therefore, ingredients used in farm-
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made fish diets need to vary from region to region based on availability, cost and 
nutritional value. It also suggests that there should be variations in ingredients use within 
the same region.   
 
5.2 Use of Commercial Fish Diets   
 In this study, Raanan was found in all the five regions surveyed. This could possibly be 
due to the fact that Raanan is the only major commercial fish diet currently being 
produced in commercial quantities in Ghana. During the present study, besides Raanan, 
only two main brands of commercial tilapia diets (Coppens and Biomar) were observed 
being used by small-scale pond fish farmers in the five selected regions for the study 
whilst over 16 different brands were recorded in the Eastern region particularly in the 
Asuogyaman District where intensive cage fish culture is commonly practised due to the 
presence of the Volta River.  This could possibly due to the low demand of these 
complete diets which are designed particularly for intensive fish culture as against the 
semi-intensive culture being practised by the small-scale pond fish farmers in the five 
surveyed regions in the present study. Artemia was unique to Ashanti and Western 
Region where it was used to feed the post larval African catfish, Clarias gariepinus.   
Hence, Artemia was not being used by farmers who spawned tilapia only. 
 
The higher cost of commercial diets with higher crude protein contents is due to the fact 
that protein is the most expensive component of fish diet (Borghesi et al., 2007; Lovell, 
1989). Much of the costs of fish diet production are due to the extensive use of fish meal 
in the diet (De-Silva et al., 2011; Tacon and De-Silva, 1997; Tacon, 1995). Generally, 
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commercial fish diets tend to be very high in protein (Lovell, 1989). Diets for fry and 
fingerlings frequently exceed 50 % crude protein. As growth rate decreases and fish age, 
protein levels in diets are decreased accordingly. Protein levels on grow-out diets often 
approach or exceed 40 % crude protein, while maintenance diets may contain as little as 
25-35 %. In addition to decreasing the protein content of the diet as fish grow, the particle 
size must increase. Commercial fish diets are manufactured as either extruded (floating or 
buoyant) or pressure-pelleted (sinking) feeds. Extruded feeds are more expensive due to 
the higher manufacturing costs (Lovell, 1989). Commercial fish diets are available in a 
variety of sizes ranging from fine crumbles for fry and fingerlings to large (6.00 mm) 
pellets.  
 
The cost of any particular brand of the commercial diet was also influenced by location. 
The farther the location from the main retailers, the more expensive it was. This was due 
to additional cost added to the original price of the diet to cover transportation. Hence, 
farmers who were remote from the main retailers or dealers would spend more money on 
fish diets and feeding. This suggests that the production cost of such farmers would 
increase greatly. Fish feed has been projected to account for at least 60 % of the total cost 
of fish production (Gabriel et al., 2007).  
 
5.3 Use of Fish Diets in the Five Regions 
The highest usage of commercial fish diets was observed in the Western region whilst the 
least was in the Ashanti region. This was mostly due to the fact that most fish farmers in 
the Western region could easily afford the cost of the commercial ones as most of these 
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farmers were found to have other lucrative businesses aside from fish farming compared 
to farmers in the other regions. Besides, most farmers in the Western region lacked the 
technical know-how in the preparation of farm-made fish diets. Farmers who utilized 
commercial diets in the Western region were of the view that they could not prepare diets 
whose quality could be comparable with that of the commercial ones. Most of them also 
expressed lack of time as a reason for not producing their own fish diets. Some also 
attributed their inability to produce their own fish diets to unavailability of required 
equipment and the necessary feed ingredients. Hence, they must of necessity patronise 
the commercial diets. On the contrary, the least of fish farmers in the Ashanti region used 
commercial fish diets only whilst they were not solely used by any farmer in the Volta 
region.     
 
The largest number of producers and users of farm-made fish diets was found in the 
Ashanti region. These farmers appeared to have a fair knowledge in fish diet preparation 
which most of them claimed they acquired through expert training and on the job 
experience.  However, the diets were found not to be nutritionally balanced as the 
producers did not follow feed formulation protocol so as to produce balanced diets that 
meet the nutritional requirements of the target fish. The largest portion of farmers who 
used both the commercial and farm-made fish diets in their production was also observed 
in the Ashanti region. This practice was to reduce cost of fish production. Some of the 
farmers who used the two types of diets either fed them to the fish alternatively or fed 
them with each type at different stages of the culture period. Others also mixed the farm-
made and the commercial diets in varying proportion to feed their fish. Those who used 
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the two types of diets at different stages of the culture period, used the expensive 
commercial ones as starter diet (i.e. feeding them to the fish at the fry/fingerling stage) 
and used the farm-made diets as the finisher (i.e. at the juvenile/grower stage till the fish 
are ready for harvest).  
 
Some farmers used the farm-made diets throughout the culture period as they could not 
afford the commercial ones. This practice was very prevalent in the Ashanti region. As 
most times the diets were not nutritionally balanced, the fish could take longer period to 
reach the harvestable size. Most of the farm-made diets consisted of ingredients that were 
not combined in a specified proportion. Some were raw agricultural wastage that was 
directly fed to the cultured fish. This could impact on water quality negatively and affect 
fish growth. Evidently, many farmers producing farm-made diets are often unaware of 
the nutrient requirements of their farmed species, notably dietary protein and energy 
levels and how these change over the production cycle (White, 2013). Formulations are 
often based on past experience (what the farmers themselves have found to work), feed 
ingredient availability and cost, and advice from other farmers, feed ingredient suppliers 
and occasionally Fisheries Extension Officers.  
 
The practice of extensive culture was highest in the Volta region. About 33.3 % of the 
respondents fed their fish with neither commercial nor farm-made diets at any given time. 
These farmers were observed to maintain large earthen ponds/reservoirs. However, they 
periodically put into the systems agricultural wastes particularly during the seasons of 
harvesting their crops or when some of their farm produce gets rotten.   
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5.4 Proximate Compositions of Ingredients Used in Diet Formulation and 
      Preparation 
Of the ingredients used in the present study, the analysed crude protein content of 
fishmeal (Tuna) was found to be higher than those of the ingredients of plant origin. The 
result is in agreement with other researchers who concluded that feed ingredients of plant 
origin often contain less protein than those of animal origin (Wu et al., 2006; Sullivan 
and Reigh, 1995; Wilson, 1991). Fishmeal had relatively high crude fibre (5.73 %). The 
fishmeal used in this study was produced from tuna wastes (fillet remains) obtained from 
processed and canned tuna. Most often such fish wastes consist of trimmings, belly flaps, 
heads, frames, fins, skins and viscera (Choudhury and Bublitz, 1996). The result is 
consistent with the findings of Munguti et al. (2012) who observed that the fibre contents 
of fillet remains of tilapia (Oreochromis spp) and those of North African catfish (Clarias 
gariepinus) were high and ranged from 6.7 to 7.3 % (Munguti et al., 2012). 
 
Plant proteins are less expensive than animal sources; however, their deficiency in 
methionine and lysine limits their use as main protein sources in fish diets (Francis et al., 
2001). Of all the plant protein feed ingredients, soybean meal is considered to be the most 
nutritious and is used as the major protein source in many fish diets to partially or totally 
replace fish meal (Lovell, 1988). It is a by-product after the removal of oil from Soya 
beans (Glycine max).  The crude protein level depends on the soybean meal quality. 
Soybean has one of the best amino acid profiles of all vegetable oil meals (Agbo, 2008; 
New, 1987). The limiting amino acids in soyabean meal are lysine, methionine and 
threonine whilst arginine and phenylalanine are in good supply (Jauncey, 1998). 
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Antinutritional factors in soybean meal, including trypsin inhibitors (Arndt et al., 1999; 
Krogdahl et al., 1994), insoluble carbohydrates (Arnesen et al., 1990) saponins (Bureau 
et al., 1998), and proteins that cause an immune response (Rumsey et al., 1994) have 
been sighted as causes for this common effect.  
 
The proximate compositions of white maize, soybean meal and wheat bran in the present 
study were in the same range as indicated by results of previous studies in Ghana (Nelson 
and Wallace, 1998). Crude fibre content of wheat bran was high and it is considered a 
limiting factor in its use in fish diet. Nutrient composition of feed ingredients depends on 
the origin, state and processing methods used (Lovell, 1998). From literature, it is 
indicated that agricultural by-products in general contain components which may affect 
their nutritive value. About 6.0 % of the total protein of soybeans reduces activities of 
trypsin and chymotrypsin, which are pancreatic enzymes and involved in protein 
digestion (Yen et al., 1977). The activity of trypsin inhibitor is not fully understood, but 
is responsible for the poor performance of certain fish species (Balogum and Ologhobo, 
1989; Alexis et al., 1985). In case of cassava, a toxic component known as Linamarin has 
to be considered. Linamarin cause cyanide poisoning, but the toxicity may be removed by 
boiling and/or sun drying (Tewe, 1991).  
 
5.5 Proximate Compositions of Farm-Made and Commercial Diets  
A good fish diet should contain protein, lipids or fats, ash (minerals), fibre, moisture, 
nitrogen free extracts (carbohydrates) and vitamins in the right proportion and formulated 
in a balanced ration which will be acceptable, palatable and durable to the fish for its 
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optimum growth (Ayuba and Iorkohol, 2013). Protein is the main growth promoting 
factor in fish diet. Protein requirement of fish is influenced by factors such as fish size, 
water temperature, feeding rate, availability and quality of natural foods and overall 
digestible energy content of the diet (Ayuba and Iorkohol, 2013; Satch, 2000; Wilson, 
2000). The values for chemical analyses of the farm-made and commercial diets were 
similar to the calculated/declared crude proteins. In all cases, the analysed values were 
higher.  These findings were in disagreement with those values of analysed crude protein 
levels of four commercial diets (Adolf calyx, Coppens, Dizengoff and Durate) by Ayuba 
and Iorkohol (2013). These researchers observed that all the analysed values on crude 
protein were less than the producers’ declared values. The values of the analyses ranged 
from 0.7 to 38.4 % less than they expected. On the other hand, similar analyses carried 
out by Opiyo et al. (2014) indicated that three commercial fish diets which were 
indicated to contain 26.0 % crude protein, proximate analyses showed that diets 1, 2 and 
3 had crude protein levels of 32.7 %, 16.0 % and 28.0 % respectively. In the present 
study, the crude proteins of the farm-made and commercial diets ranged from 1.71 to 5.1 
% greater than the expected with the greatest deviation occurring in farm-made diet B. 
However, all the analysed crude protein levels for both the farm-made and commercial 
diets were within the recommended range for juvenile and adult O. niloticus (El-Sayed, 
2006; Lim and Webster, 2006; Fitzsimmons, 2005; Shiau, 2002; NRC, 1993). The 
differences between the analysed values and indicated values of crude protein in the diets 
could be an indication of lack of proper proximate analysis of ingredients before feed 
formulation and production (Opiyo et al., 2014). Variations in feed ingredients might 
occur due to regionalism and seasonality in availability of the ingredients (Munguti et al. 
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2012).  For this reason, feed producers need to carry out routine proximate analyses 
particularly when a new batch of fish feed ingredients is procured.  
 
Lipids are primarily included in formulated diets to maximize their protein sparing effect 
by being a source of energy (Hasan, 2001).  Dietary lipids facilitate the absorption of fat 
soluble vitamins, play an important role in membrane structure and function, serve as 
precursors for steroid hormones and prostaglandins, and serve as metabolizable sources 
of essential fatty acids. The observed lipid levels of the two commercial diets, Raanan 
and Coppens were below the minimum recommended values of 10-15 % (El-Sayed, 
2006; Lim and Webster, 2006; Fitzsimmons, 2005 and Shiau, 2002). However, Luquet 
(2000) also stated that dietary lipid levels of 5 to 6 % are often used in tilapia diet.  
 
Fibre provides physical bulk to the diet. An appreciable amount of fibre in the diet 
permits better binding and moderates the passage of feed through the alimentary canal. 
However, De Silva and Anderson (1995) noted that it was not desirable to have fibre 
content above 8-12 % in diets for fish, since the increase in fibre content would 
consequently result in the decrease of the quality of usable nutrient in the diet. A high 
fibre and ash content reduces the digestibility of other ingredients in the diet resulting in 
poor growth of the fish. The analysed crude fibre contents of all the diets evaluated were 
within the dietary requirement for O. niloticus.   
 
The percentage phosphorus contents of all the diets were within range for complete fish 
diets (Lovell, 1989). Although farm-made diet E was prepared by mixing equal portions 
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of farm-made diet B and Raanan, the values obtained for the chemical analyses of E were 
not equal to those of the mean of the two mixed diets. However, all the parameters were 
similar to those of the other diets.  
 
5.6 Growth Performance of the Cultured O. niloticus 
The growth performance and feed utilization efficiency of juvenile O. niloticus are 
affected by food quantity and quality, genetic make-up, sex of the fish and their 
interaction (Noor et al., 2010; Gjedrem, 1997). The initial body weights and body lengths 
of the experimental fish recorded at the commencement of the experiment were similar 
and were not significantly different (ANOVA, p > 0.05). Hence, the performance 
differences observed among treatments at the end of the growth trial was due mainly to 
dietary effect.  
 
The results of the present study showed that all the experimental diets were accepted to 
varying degrees by the cultured fish. Hence, the constituents of both the farm-made and 
the commercial diets affected the palatability of the diets. The differences in the quality 
of the diets could be due to the composition and the processing technique employed in 
their production which might have enhanced the palatability and nutrient digestibility of 
the different diets to varying extent. The extrusion of the commercial diets during their 
production compared to the farm-made ones might have improved the performance of the 
former.  Heat treatment involved in typical moist extrusion processing used for fish diet 
may be sufficient to inactivate most of the trypsin inhibitor activity in unheated soybean 
meal, and to increase digestibility of the protein in untoasted defatted soybean meal 
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(white flakes) to approximately the same level as found for soybean meal and fish meal 
(Romarheim et al.,  2005). The growth performance and feed efficiency of animals fed 
extruded diets is thought to improve. Different processing techniques can reduce anti-
nutritional factors and thereby increase palatability (Workagegn et al., 2013; Azzaza et 
al., 2008).  
 
Extrusion conditions might significantly affected final weight, feed efficiency, protein 
productive value and energy retention particularly of O. niloticus fed Raanan in this 
study. Similar results were reported for rainbow trout (Barrows et al., 2007), channel 
catfish (Peres et al., 2003) and carp (Viola et al., 1983). A beneficial effect of heating of 
soyabean meal on weight gain, feed intake and feed efficiency of channel catfish was 
observed (Peres et al., 2003). Growth rates of carp were reduced when fed diets 
containing under-heated soybean meal (Viola et al., 1983). The variations in growth 
performance and feed utilization efficiency in this study could also be attributed to 
differences in the quality of the various diets in terms of nutrient composition 
(Workagegn et al., 2014).  
 
Even though Coppens had the highest crude protein content, this was not reflected in the 
growth performance and feed efficiency of the O. niloticus it was fed with. This could 
possibly be due to the fact that the diet lacked sufficient essential amino acids to support 
fish growth. This supports the observation made by Santiago and Lovell, (1988) that fish 
do not have a specific requirement for crude protein per se, but rather they need the right 
combination of essential amino acids.  Essential amino acid requirements can be met by 
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the use of a balance of both plant and animal proteins, and if necessary, by the inclusion 
of synthetic amino acids in the complete diet (Jauncey et al., 1983).  An indispensable 
amino acid deficiency may cause reduced growth and poor feed conversion (Halver and 
Hardy, 2002; Wilson and Halver, 1986). Therefore, satisfying the indispensable amino 
acid requirements of a species is outmost importance in preparing well-balanced diets. 
This observation suggests that O. niloticus performs better when fed a diet containing the 
complete requirements of amino acids for tilapia (Santiago et al., 1988).  
 
The low ash content of Coppens could also be responsible for the poor growth 
performance of the fish it was fed with. In experimental diets, ash is a source of calcium 
and phosphorus (Abowei and Ekubo, 2011).  Hence, essential mineral elements such as 
calcium and phosphorous that promote growth in fish were insufficient in Coppens. Ali 
and Jauncey (2004) noted a better growth performance of C gariepinus on diet containing 
9.3 % ash content, whilst Alam et al. (2012) opined that ash content in the feed of C. 
gariepinus should not be less than 8.0 %. High ash content of > 12.0 has been reported to 
produce better growth performance in Clarias species (Corn Elio et al., 2014; 
Kiriratnikom and Kiriratnikom, 2012).  
 
The results of the present study contradict that of other researchers in comparing Coppens 
with farm-made fish diets. Mustapha et al. (2014) observed that C. gariepinus gave 
significantly better growth performance when fed Coppens than when fed farm-made 
diet. Coppens has been reported to produce better growth performance in various species 
of fish when compared with local fish diets. These include the work of Shapawi et al. 
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(2011) who compared growth performance of humpback grouper Cromileptis altivelis fed 
farm-made diets and Coppens, and Ahmed et al. (2012) who showed that commercial 
fish diets enhanced better growth performance of the fingerlings of Labeo rohita. The 
comparable performance of the farm-made diets to Coppens in the current study could be 
attributed to the quality of the former.  
 
5.7 Feed and Nutrient Efficiency of the Cultured O. niloticus 
The most efficient feed conversion was observed in fish fed Raanan diet whilst the least 
occurred in fish fed farm-made diet B. Fish fed farm-made diet B (diet without 
supplements), showed higher feed conversion ratio (FCR), lower protein efficiency ratio 
(PER) and lower protein productive value (PPV %) (3.26, 1.27 and 20.44 % respectively) 
when compare with on-farm diet A (2.96, 1.37 and 24.89 respectively). These findings 
are comparable to those of various researchers who reported improved growth of fish 
with amino acid incorporation at similar inclusion levels of plant protein (Furuya et al., 
2004; El-Saidy and Gaber, 2002; Mukhopadhyay and Ray, 2001; Polat, 1999). 
    
The results of this study are also in agreement with that of Zhou et al. (2006). PER 
increased with increasing dietary level of methionine from 0.61 % to 1.05 % and 
decreased with further increase (1.68 %). Luo et al. (2005) from their study on 
methionine requirement of juvenile grouper, they observed the poorest FCR (2.38), the 
lowest PER (0.93) and low PPV % (16.3 %) in fish fed the diet containing least (0.55 %) 
methionine. These parameters improved proportionally with the methionine 
supplementation up to 1.34 % and showed no significant difference for fish fed the 
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dietary methionine level ranging from 1.34 % to 1.81 %. Significant improvement in PPV 
% was observed when level of methionine supplementation increased to 1.34 and 1.81 % 
to be 28.8 and 31.6 % respectively. Also, Mai et al. (2006) from their study on dietary 
methionine requirement of large yellow croaker, they found that the PER of fish were 
significantly improved by supplementation with methionine. Methionine deficiency 
resulted in reduced growth and feed efficiency, as well as in cataract of salmon (Cowey et 
al., 1992; Rumsey et al., 1983; Walton et al., 1982).   
  
Supplementing crystalline amino acids in fish diets has had variable success (Agbo, 
2008). Shiau et al. (1989) observed that male tilapia (O. niloticus x O. aureus) fed diets 
in which 100 % of the fish meal was replaced with soyabean meal (SBM), either with or 
without methionine supplementation had significantly lower weight gain, FCR and 
protein digestibility than in groups fed diets containing fish meal as the sole source of 
protein. Andrews and Page (1974) stated no improvement in growth of channel catfish 
when L-methionine was supplemented to a soybean meal based diet and also Teshima 
and Kanazawa (1988) did not observe improvement in fish growth when they 
supplemented SBM with the deficient essential amino acid, and therefore concluded that 
it was unnecessary. In the present study, there was no significant difference between fish 
fed diet supplemented with amino acids and the one that was not. Bai and Gatlin (1994) 
also reported that addition of supplemental L-lysine to a diet with 25 % crude protein 
from soy did not improve growth of channel catfish.  
 
Studies in Israel have suggested that despite the essentiality of vitamins in dietary 
formulations, tilapia grown in ponds, cages or concrete tanks at densities as high as 100 
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fish m-2 and yield up to 20 tonnes/ha did not show any beneficial effects from the 
addition of dietary vitamin supplements (Viola, 1989). Many farmed fish species, 
including Indian major carps, are filter-feeders and derive much of vitamin and mineral 
requirements by consuming fine particulate matter (phytoplankton, zooplankton, bacteria 
and detritus) (Coleman and Edwards, 1987). These findings were in agreement with the 
present study as the addition of mineral and vitamin premixes did not increase growth 
performance and feed efficiency significantly.  
  
The unexpected poor growth performance and feed efficiency observed in fish fed diet E 
(a 1:1 mixture of farm-made diet B and Raanan) could be due to the adulteration of the 
Raanan diet. Diet B was not supplemented with essential amino acids, it contained high 
level of antinutritional factors by virtue of the ingredients used in its preparation and 
besides, it was not processed by any means (particularly heating).  Hence, the mixing of 
B with Raanan in a ratio of 1:1 diluted the latter to the extent that there was reduction in 
nutrient availability as confirmed by Azzaza et al., 2011; Aderibigbe et al., 1997; Hajos 
et al., 1995; Reddy and Pierson, 1995, who reported that diets with higher concentration 
of antinutritional factors reduces the availability of nutrients which in turn reduces the 
growth performance of fish. Also, Lim and Dominy (1991) reported that reduced growth 
response and feed utilization in various warm-water aquaculture species fed diets in 
which fish meal was replaced with oilseed meals have been explained by sub-optimal 
amino acid balance, inadequate levels of phosphorus, inadequate energy, low feed intake 
caused by poor palatability, presence of endogenous antinutrients or dietary level of fish 
oil (Lim and Dominy, 1991). The poor performance of diet E could be due to any of these 
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factors. Also, De Silva et al. (1989) observed that acceptability of feed by fish could be 
affected by increasing levels of plant material since the texture and taste of the diets are 
bound to differ.  
 
In this study, the highest survival rate was achieved in fish fed Raanan and the least in 
Coppens. However, there were no significant differences among dietary treatments. Most 
of the mortality observed during the growth trials could not be due to dietary treatment as 
mortality was mostly experienced a day after measurements of fish growth. Hence, 
mortalities could be attributed to handling stress. This observation was in agreement with 
findings of Attipoe et al. (2009). These researchers reported a survival of 86.50 to 87.43 
% in earthen ponds when Nile tilapia was fed with three different diets formulated from 
local agro-industrial by-products. They also attributed part of the mortality to predation 
particularly by predatory birds. In the current study, bird predation did not occur as the 
hapas used in culturing the fish were fully covered with nylon nets. Besides handling 
stress, another factor that contributed to mortality in this study was escape of fish from 
some of the replicates (hapas) as they were being taking out of the culture system to 
measure growth during the study period.  
 
Although specific feeding trial durations are not universally specified, they generally 
need to last long enough for any potential significant differences among the diets to 
materialize (Weatherup and McCracken, 1999). In a study by De Francesco et al. (2004), 
differences in trout growth performance between fish meal and plant-based diets became 
apparent after 12 weeks. In the present study significant differences occurred after 16 
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weeks. In a study by Barnes et al. (2012) in which fish meal was replaced with high 
protein distillers dried grain (HPDDG) in juvenile rainbow trout diets, the experiment 
lasted over 10 weeks for significant differences to occur.  
 
5.8 Length-Weight Relationship of the Cultured O. niloticus 
The present work revealed that O. niloticus followed the cube law completely in all the 
dietary treatments except in Raanan where there was a positive departure by 0.1. 
Statistical analysis of the LWR of the current study showed that O. niloticus fed both the 
farm-made and commercial diets showed isometric growth. These results are comparable 
with the findings of other researchers who worked on other species of tilapia. Mgaya et 
al. (2005) recorded values of b in fresh water floodplain lakes in Ruwe ponds for O. 
urolepis ranged from 2.7-3.0.  Haruna (2006) recorded a b value in T. zillii of 2.7 and 3.2 
for wet and dry seasons respectively. The values obtained by these researchers are in 
agreement with the findings of this study. The values of b in this study were within the 
range of 2 - 4 recommended by (Bagenal and Tesch, 1978; Martin, 1949; Hile, 1936) as 
ideal for fresh water fishes and an ideal fish maintain the shape b = 3 (Golam and Al-
Misned, 2013). Values of b above 3 are possible in some conditions such as stress free 
environments (Prasad and Anvar, 2007). The good water quality parameters recorded in 
all the dietary treatments coupled with food availability and feeding characteristics could 
account for the high b values obtained in the present study.  
 
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5.9 Condition Factor of the Cultured O. niloticus 
In the present study, the K values of O. niloticus in all the dietary treatments were greater 
than 1. A condition factor higher than one suggests good fish health condition and 
indicates an isometric growth, which is desirable in a fish farm (Ayode, 2011). There 
may be differences in the condition factor due to sex (Olurin and Aderibigbe, 2006). This 
was not applicable to the results of the present study as all-male O. niloticus were utilized 
in all the dietary treatments. In this study the LWR was found to be in a linear form 
conforming to the general formula expressing the relationship between the length and 
weight of fishes. This could be attributed to the good water quality maintained and the 
quality of diets that contributed to the steady increase in their weight and length. The fish 
from all the treatments were in good condition and healthy. This suggests that all the fish 
diets used in this study will be suitable for commercial production of O. niloticus. 
 
5.10 State of Health of the Cultured O. niloticus 
Harvested fish from all dietary treatments at the end of the experiment were in good 
health condition with no physical deformities. No abnormalities occurred in the eyes, 
fins, gills, guts, kidneys, livers, pseudobranchs, opercles or spleens in any of the fish fed 
the various diets including farm-made diet B which was not supplemented with vitamin 
and mineral premixes, and essential amino acids. These results support the findings of 
other researchers who reported that vitamin supplementation is not necessary for 
optimum growth and health of tilapia in semi-intensive farming systems where natural 
foods are available (El-Sayed, 2006; Lim and Webster, 2006).  
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Vitamins are important nutrients in the supplementary diets of most fish species 
(Dabrowski and Blom, 1994). The absence or relative deficiency of vitamins in the diets 
leads to decrease fish appetite, metabolic activities and consequently to the onset of 
diseases (Abdelghany, 1998). Several vitamin requirements of tilapia are known to be 
affected by other dietary factors. For example, the vitamin E requirement is influenced by 
dietary lipid level with Nile tilapia requiring 50-100 mg/kg when fed diets with 5 percent 
lipid and increased to 500 mg/kg diet for diets with 10-15 percent lipid (Lim and 
Webster, 2006). Vitamin deficiency symptoms of tilapia under controlled culture 
conditions have been extensively reviewed by Jauncey (2000), El-Sayed (2006) and Lim 
and Webster (2006). Under culture conditions, vitamin deficiency signs are not a 
common occurrence in tilapia. In fact, several studies have reported on the “non-
essentiality” of adding vitamin premixes to tilapia diets (Jauncey, 2000). Vitamins 
obtained from natural food in fertilized ponds, endogenous vitamins present in feed 
ingredients used in tilapia feeds and the microbial biosynthesis of some vitamins in the 
gut are all likely to contribute significantly to the vitamin requirements of tilapia. 
 
Mineral deficiencies are difficult to assess in tilapia as most trace elements are obtained 
both from the dietary ingredients and from the culture water (Dabrowska et al., 1989). 
Besides, tilapia could absorb minerals from the culture water and there are also minerals 
in feed ingredients (Stickney, 1997). Deficiency signs of farmed tilapia may occur when 
fish are fed nutrient deficient diets or raised in a low nutrient-input culture system 
(Dabrowska et al., 1989). Since no deficiency signs were observed in any of the fish of 
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the various dietary treatments in the present study, it suggests that none of the diets was 
deficient in nutrient.  
 
Also, histopathological examination of the intestines and liver did not reveal any 
morphological abnormality. Since the Nile tilapia fed the unsupplemented amino acid and 
vitamin-mineral premix diet did not show any disease condition, it suggests that the 
various ingredients used in the diet formulation, contributed significant amount of 
essential amino acids, vitamin and minerals to the prepared diet. A similar observation 
made by Agbo (2008) stated that a careful selection of different plant protein sources in 
various combinations could be a means of compensating for essential amino acid 
deficiency in any single protein source and also prevent a high inclusion level of any 
single antinutritional factor in the diet.    
 
Absence of both external and internal abnormalities in O. niloticus in all the dietary 
treatments could also be attributed to the quality control measures that were applied to the 
diets during the current study, which prevented the diets from being infested with 
aflatoxin. Cha `vez-Sa `nchez  et al. (1994) reported that O. niloticus fingerlings were 
able to tolerate the immediate effect of aflatoxin but later the fish developed external and 
internal abnormalities. Different external manifestations of abnormality in fish fed with 
aflatoxin contaminated feeds were eye opacity leading to cataract and blindness, lesions 
on the body surface, fin and tail rot, yellowing of the body surface of the fish, abnormal 
swimming, feeble and stationary on one place, and reduced appetite (Cha `vez-Sa `nchez  
et al. 1994). These manifestations became more intense as aflatoxin level in the feed 
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increased. Observed manifestations of aflatoxin in the liver of fish were abnormal 
enlargement and yellowing as well as collapsed liver in newly dead fish (Royes and 
Yanong, 2002; Wu, 1998; Ferguson, 1989; Roberts, 1978). Joner (2000) described the 
effect of aflatoxin in the liver as follows: first, aflatoxin is absorbed from the diet in the 
alimentary canal and is passed to different organs. The principal target organ for 
aflatoxins is the liver. After the invasion of aflatoxins into the liver, lipids infiltrate 
hepatocyte and leads to necrosis or liver cell death. The main reason for this is that 
aflatoxin metabolites react negatively with different cell proteins, which leads to 
inhibition of carbohydrate and lipid metabolism and protein synthesis. In relation with the 
decrease in liver function, there is a derangement of the blood clotting mechanism, 
jaundice, and a decrease in essential serum proteins synthesized by the liver. 
 
5.11 Whole Body Composition of the Cultured O. niloticus 
In this study, dietary treatments affected whole body composition. Among all the 
parameters, it was only moisture content that was not significantly affected by dietary 
treatment. Comparing the O. niloticus fed the farm-made diet supplemented with amino 
acids (diet A) and those fed diet B, the former had a higher final body crude protein and 
reduced fat content. This was in agreement with observation made by Cheng et al. (2003) 
that lysine supplementation in plant protein-based diets increased crude protein and 
reduced fat in fish body. Rodehutscord et al., (2000) found that the crude protein of trout 
body increased linearly with increased dietary lysine supplementation disregarding 
dietary crude protein levels and fat decreased linearly with increased lysine 
supplementation. Schwarz et al. (1998) in their study on carp (Cyprinus carpio L.) found 
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that whole body protein and lipid content were significantly affected by dietary 
methionine levels (p < 0.01), the whole body protein increased significantly from 14.7 % 
T-I to 16.3 % T-IV with increasing dietary methionine levels, whilst fat decreased from 
13.9 to 11.5 % T-V with increasing dietary methionine levels, (Where T-I to T-V are 
treatments with ascending methionine levels 0.49, 0.61, 0.79, 1.08 and 1.34 %).  Luo et 
al. (2005) from their study on methionine requirement of juvenile grouper, they observed 
that carcass protein content showed an increasing trend with increasing dietary 
methionine levels but moisture content decreased. 
 
There was significant increase in crude protein content of the cultured fish in all the 
dietary treatments in comparison with that of the initial carcass composition of the 
experimental fish. Similar results were reported by El-Saidy and Gaber (2002) in Nile 
tilapia, Mukhopaddhyay and Ray (2001) in rohu and Polat (1999) in T. zillii.   
 
Hepatosomatic index (HSI) is positively related to carbohydrate levels in the diet (Kim 
and Kaushik, 1992; Daniels and Robinson, 1986). Hence, it was not surprising that in this 
study, fish fed coppens had significantly higher HSI. It was also expected that fish fed 
farm-made diet B should have a high HSI since they had the least growth rate and lowest 
feed efficiency although they were not significantly different from the other treatments 
except for the feed efficiency, which was significantly lower than that of fish fed Raanan. 
Higher HSIs have also been associated with slower growth rates and decreased feed 
efficiency (Takeuchi and Watanabe, 1982) both of which describe the fish fed farm-made 
diet B. The findings of the current study are in agreement with that of Barnes et al. 
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(2012), who reported that there were no significant differences in HSI among treatments 
when diet containing different levels of Distillers Dried Grains with Solubles (DDGSs) 
were fed to juvenile rainbow trout (Onchorynchus mykiss). The hepatosomatic index 
either slightly decreased or showed no effect, from dietary DDGS in tilapia (O. niloticus) 
(Schaffer et al., 2010, 2009) and was also unaffected by dietary protein in common carp 
(Cyprinuc carpo) (Fine et al., 1996).   
 
5.12 Effect of the Diets on Water Quality  
All the diets had similar effect on the quality of hapa water and all recorded values were 
within the suitable ranges for O. niloticus (Swann, 2007, Hussain, 2004; Suresh, 2003; 
Popma and Masser, 1999; Stickney, 1979). The suitable water quality maintained in all 
the dietary treatments during the present study could be attributed to prevention of diet 
waste during the feeding process as appropriate pellet sizes that the fish could ingest were 
administered. Besides, the diets were free of fines avoiding poor ingestion by the fish as 
well as dispersion of the fines within the water column. These prevented the diets from 
sinking and accumulating at the bottom of the hapas to impact negatively on water 
quality. This observation is in accordance with the findings of Ofori (2001) who reported 
that the risk of water quality deterioration and an associated reduction in fish growth is 
ameliorated when the accumulation of organic matter is minimized. 
 
5.13 Apparent Nutrient Digestibility of Diets 
The general reduction in the nutrients of the faeces compared to that of both the farm-
made and commercial diets fed to O. niloticus observed is in agreement with other 
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researchers (Jimoh et al., 2010; Adeparusi and Jimoh, 2002). This suggests that some 
amount of nutrients in all the diets were absorbed and made available for metabolism in 
the fish. Nutrient digestibility as well as its absorption and retention in the body 
determine growth performance and feed utilization efficiency in fish (Aanyu et al., 2014; 
Deganp and Yehuda, 1999; Guillaume and Choubert, 1999). The nutritive value of a diet 
depends not only on its nutrient content but also on the capacity of the animal to digest 
and absorb the nutrients (Rust, 2003; Cook et al., 2000). Nutrients absorbed in the 
digestive system are first used for maintenance of body functions and the surplus is 
retained in the body. Excess protein is deposited in the body for growth whilst excess 
energy is stored as fat (Cook et al., 2000; Jobling, 1994). In the present study, a higher 
crude protein deposition and lower fat content were observed in the carcass of fish fed 
farm-made diet A and Raanan. The results suggest that farm-made diet A and Raanan 
were the most efficiently assimilated. Deposition of protein in fish is known to result in 
fish growth. The higher the protein deposition, the higher the weight gain (Aanyu et al., 
2014; Lupatsch et al., 2003; Sveier et al., 2000).  
 
The variations in apparent digestibility coefficients (ADCs) of the various components in 
the diets used in this study could be explained by differences in the chemical 
compositions and processing of the diets. In general, the ADCs of all the parameters 
except ash in all the diets were high (above 60 %).  This could primarily due to the 
relatively low fibre and ash contents of the diets. Furulehi and Yone (1982) observed that 
low levels of dietary fibre improved digestibility of nutrients through increased gut transit 
time and enzymatic activity. The digestibility of the commercial diets was further 
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enhanced by extrusion compared to the farm-made ones which were just pelleted. Mild 
extrusion cooking conditions can enhance digestibility of plant protein (Hakansson et al., 
1987; Srihara and Alexander, 1984). As a result, extrusion normally improves nutrient 
digestibility, palatability, pellet durability, water stability and pellet storage life (Barrows 
and Hardy, 2001).  
 
Protein quality of dietary protein sources depends on the amino acid composition and 
their digestibility (Halver and Hardy, 2002). Deficiency of essential amino acid leads to 
poor utilization of the dietary protein and consequently reduces growth and decreases 
feed efficiency. Therefore, this could explain why Coppens performed relatively poorly 
in terms of growth performance and feed efficiency, regardless of its high apparent 
protein digestibility in the present study. The digestion coefficients for protein-rich 
feedstuffs are usually in the range of 75 to 95 % (NRC, 1983). The apparent digestibility 
of protein (77.49 % - 87.02 %) of both the farm-made and commercial diets in this study 
is within this range. Apparent protein digestibility tends to be depressed as the 
concentration of dietary carbohydrate increases (NRC, 1993). This was not observed in 
this study and the findings were in agreement with that of Agbo (2008). The higher 
apparent digestibility of protein in the fish fed the extruded diets (Coppens and Raanan) 
compare with those fed the un-extruded ones (farm-made diets) are in agreement with the 
findings of Ma et al. (2015).  
 
The higher crude fibre digestibility coefficient than that of crude carbohydrate observed 
in this study could be due to the natural feeding habit of tilapia that consists mainly of 
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plant material (Pullin, 1983). O. aureus was observed to digest highly fibrous feedstuffs 
such as alfalfa meal (Mgbenka and Lovell, 1987). Crack and cook processing method 
improved the digestibility of crude fibre (Jimoh et al., 2010; Adeparusi and Jimoh, 2002).  
Fibre digestibility of O. niloticus fed lima bean diet was improved with toasting and 
autoclaving (Adeparusi and Jimoh, 2002). Hence, it was expected in the current study 
that Raanan like Coppens should have yielded higher crude fibre ADC than what was 
observed. This might probably be due to the higher ash content of Raanan (Table 4.4). 
The same reason could explain why the apparent dry matter digestibility coefficient of 
Raanan was significantly lower than that of Coppens although both diets were extruded. 
High ash content of diet is known to decrease dry matter ADCs (Bureau et al., 1999).  
The comparatively low ADCs of ash recorded in all the dietary treatments could be due 
to the fact that fish do not need high quantity of minerals from their diets (Adeparusi and 
Komolafe, 2006).       
 
Lipid digestibility in all the dietary treatments was high (81.46 % - 93.90 %) and the 
values were found to be in line with what were reported by Jimoh et al. (2010) for O. 
niloticus and Hossain et al. (1992) for rainbow trout.  Andrew et al. (1978) reported that 
the ability to digest fat appears to be influenced by temperature and the level of fat in the 
diet. The high lipid digestibility by O. niloticus in the farm-made diets shows that the 
palm oil used in the formulation and production of the diets was well utilized. This is a 
good phenomenon since lipid can also have a sparing effect on protein. It also suggests 
that plant oil which is cheaper could be a better alternative to animal oil in tilapia diet. 
 
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The high apparent carbohydrate digestibility coefficients (65.44 % - 85.94 %) recorded in 
this study were in agreement with the observation of Popma (1982) that warm water fish 
like O. niloticus absorbs 60 % or more of raw corn starch . The result however deviated 
from the low carbohydrate digestibility recorded by Jimoh et al. (2010) as well as 
Adeparusi and Jimoh (2002) for O. niloticus fed lima bean diets. The digestibility of 
carbohydrates has been shown to vary with their complexity, source, treatment and level 
of inclusion in the diet (Jimoh et al., 2010; Cho and Slinger, 1979; Lovell, 1977; Phillip, 
1972). The result of the present study agrees with the observation of Lovell (1988) that 
tilapia have ability to digest carbohydrate relatively well in feedstuff but not as well as fat 
or protein. In this study, the ADCs of fat and protein for all the dietary treatments were 
higher than their corresponding values for carbohydrate. Digestibility of carbohydrate 
was high in O. niloticus fed farm-made diet A, although highest in Coppens. This would 
lead to maximum utilization of available protein as a result of protein sparing-action of 
carbohydrate. This could probably explain why the final carcass protein deposition of O. 
niloticus fed farm-made diet A was significantly high.   
 
The apparent digestibility coefficients of gross energy recorded in this study except in 
Raanan were higher than the values observed by Jimoh et al. (2010) and Fagbenro (1998) 
of jackbean meal diets fed to O. niloticus. Lovell and Durve (1982) observed that cooking 
improved gross energy digestibility. However, this was not shown in the Raanan diet, as 
the non-heat treated farm-made diets recorded higher values than the former. The least 
digestibility of energy in Raanan in this study could be due to the low energy content of 
the diet as indicated by analysis. The extrusion of the commercial diets was expected to 
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improve their digestibility compare to the farm-made ones which were not heat-processed 
in any form.    
 
The apparent digestibility coefficients of dry matter, carbohydrate, fibre, ash and gross 
energy of farm-made diet A were higher than those of farm-made diet B. This could 
possibly due to the inclusion of lysine and methionine in diet A.    
 
5.14 Cost Effectiveness of Diets 
The cost-effectiveness analyses of the various diets in this study indicated that the farm-
made diets were more profitable than the commercial ones, and the amino acid 
supplemented diet was the most profitable whilst Coppens was the least profitable. These 
findings are consistent with other studies which indicated that nutritionally balanced 
farm-made fish diets were cost-effective in the production of O. niloticus in semi-
intensive fertilized ponds (Opiyo et al., 2014; Gabriel et al., 2007; Liti et al., 2005). 
However, the results of the present study are in disagreement with that of Nguyen (2013) 
who observed that although using farm-made diets appears to be the cheaper option, and 
switching to them reduces production costs, they are less efficient in terms of growth and 
FCR; thus, in terms of real production costs (cost/kg fish produced), they are more 
expensive to use. His study demonstrated that the total cost of production using farm-
made diets was US$0.88/kg fish, whereas it was US$0.79/kg fish for farmers using 
commercially manufactured diets or a combination of commercially manufactured and 
farm-made diets (Nguyen, 2013).  The findings of the current study also contradict that of 
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this researcher, who reported that although reverting to farm-made diets may reduce diet 
costs, farmers need to recognize that there will be a concomitant reduction in profits. 
 
In the present study, even though the Raanan was highest in extrapolated fish yield (7, 
920 kg ha-1 yr-1) it was 26.26 % less profitable than farm-made diet A (5, 407.99 kg ha-1 
yr-1) and 23.23 % less profitable than farm-made diet B which gave the least yield (4, 
856.00 kg ha-1 yr-1). Diet A was 135.85 % more profitable than Coppens (5, 096 kg ha-1 
yr-1) and diet B was 130.19 % more profitable than Coppens.  The least profit of Coppens 
was likely due to the high cost of the diet without commensurate increase in yields when 
compared to Raanan. It was more profitable to feed Nile tilapia with either the 
supplemented or unsupplemented amino acid or vitamin/mineral premixes diet than an 
equal mixture of the unsupplemented diet and Raanan. In this study, there were no 
significant differences between the growth rate and feed efficiency of the farm-made 
diets and the Coppens which was the most expensive diet among all. Hence, the use of 
the two types of diets to raise a fish to market size of 200 g by Ghanaian standards 
(Agbo, 2008) may last over the same culture period. This suggests that using the farm-
made diets will reduce the production cost of Nile tilapia and consequently increase the 
profit margin of the fish farmer. This will immensely benefit the small and medium scale 
semi-intensive farmers who constitute the majority of fish farmers in Ghana.       
 
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CHAPTER 6.0 CONCLUSION AND RECOMMENDATIONS 
6.1 Conclusion      
The results of this study showed that in all, 32 feed ingredients and 5 feed 
supplements/additives were being used by small-scale pond fish farmers in Ashanti, 
Brong-Ahafo, Central, Volta and Western Region to produce farm-made fish diets. Some 
of these ingredients were being used in all the regions surveyed whilst others are peculiar 
to one or two regions. There were both inter- and intra- regional differences in the price 
per kilogramme of almost all the ingredients. Ingredients such as Bean (Phaseolus 
vulgaris) husks, Bean (Phaseolus vulgaris) leaves, Birds (dead poultry), Brewery waste, 
Cassava (Manihot esculenta) leaves, Kitchen wastes and Potato (Solanum tuberosum) 
leaves were being sourced at no cost.  
 
The largest usage of farm-made fish diets was found in the Ashanti Region. However, the 
diets were found not to be nutritionally balanced as the producers did not follow standard 
feed formulation protocol so as to produce balanced diets that meet the nutritional 
requirements of the target fish. Of the 138 farmers using fish diets in all the regions 
surveyed, 37.7 % used commercial diets, 26.8 % used farm-made diets whilst 35.5 % 
used both.  
 
Only 3 major commercial fish diets (Raanan, Coppens and Biomar) out of about 16 
commercial fish diets (Agricare, Alleraqua, Aquafeed, Aquaxcel, Beacon Hill, Bioaqua, 
Biomar, Coppens, Multi Feed, Nicoluzzi, Pirá, Proaqua, Raanan, Skretting, Tilalia and 
Zeigler) currently available in the country were being used in the five regions (Ashanti, 
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Brong-Ahafo, Central, Volta and Western) surveyed. Raanan was most used and it 
constituted about 86.2 % of all used commercial diets.  Biomar was least used (about 2.0 
%). The price per kilogramme of the commercial fish diets was influenced by brand, 
crude protein content and location. Those with higher crude proteins were more 
expensive although of the same brand. The highest usage of commercial fish diets was 
observed in the Western Region whilst the least was in the Ashanti Region.  
 
The largest (48.2 %) portion of farmers in Ashanti used both commercial and farm-made 
fish diets in their production. Some of the farmers who used the two types either fed them 
to the fish alternatively or fed them at different stages of the culture period. They used the 
expensive commercial ones as starter diet (i.e. feeding them to the fish at the fingerling 
stage) and used the farm-made diets as the finisher (i.e. at the juvenile till the fish are 
ready for harvesting). Some farmers for un-affordability of the commercial fish diets used 
the farm-made diets throughout the culture period. This practice was very prevalent in the 
Ashanti. Most of the farm-made diets consisted of ingredients that were not combined in 
a specified proportion to produce diets.  Some were raw agricultural wastage that was 
directly fed to the cultured fish. The practice of extensive culture system was highest in 
the Volta. About 33.3 % of the respondents in the region fed their fish with neither 
commercial nor farm-made diets at any given time. These farmers were observed to 
maintain large earthen ponds/reservoirs.    
 
The proximate compositions analyses of the two most commonly used commercial fish 
diets in the present study together with results from other researchers revealed that not all 
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commercial fish diets available on the Ghanaian market are good enough to enhance 
good growth of O. niloticus as the chemical analyses of the nutritional compositions 
indicated that some of the parameters were different from what the producers declared on 
the labels of their feed bags.  
 
The costs associated with the use of commercial fish diets by small-scale pond fish 
farmers are high,  and in terms of fish growth and economic returns, the use of 
appropriately prepared farm-made diets will be a better alternative. The most obvious 
observation was the relatively poor performance of Coppens although it was the most 
expensive. Therefore, cost of commercial fish diets cannot necessarily be translated into 
good quality. The farm-made diet A which was supplemented with amino acids, 
vitamin/mineral premixes has the best prospects based on growth performance, nutrient 
utilization and economic benefits. Amino acids unsupplemented farm-made diets could 
be used to produce acceptable fish growth and feed conversion ratios of Nile tilapia in 
semi-intensive production systems, where autotrophic and heterotrophic food material 
may supply the deficient amino acids. Simple heat processing of the unsupplemented diet 
(B) under field conditions as suggested by Agbo (2008) will improve on the performance 
of the diet and thereby reducing the cost of fish diet production since the additional cost 
of including supplements will be eliminated.   
 
The highest (165.0 g) weight gain was observed in the fish fed Raanan whilst the least 
(107.8 g) occurred in fish fed farm-made diet B. There was no significant difference in 
specific growth rate among all dietary treatments. The feed conversion ratio (FCR) 
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ranged from 2.92 to 3.26, with Raanan recording the least and farm-made diet B the 
highest. There were no significant differences in feed intake and protein efficiency ratio 
among treatments. Energy retention ranged from 8.32 to 15.32 % with fish fed Raanan 
being significantly higher and those fed Coppens being significantly lower. The crude 
protein of whole body proximate analyses of the harvested fish from the dietary 
treatments ranged from 16.20 to 18.46 % and analyses indicated that fish fed farm-made 
diet A was significantly (ANOVA, p < 0.05) higher whilst there was no significant 
difference between fish fed farm-made diets B and E. The fat contents of the treatments 
ranged from 3.04 to 4.20 % with diet B and Coppens being significantly higher. The 
gross energy of all the dietary treatments was similar and they ranged between 5.47 to 
5.95 kJ g-1.  
 
The apparent digestibility coefficients of the nutrients in both the farm-made and 
commercial diets in this study were high (> 60.0 %). Digestibility was found to be 
affected by the chemical composition of the diets and their treatments. Digestibility of 
nutrients was relatively lower in diets with relatively high ash content. Digestibility of 
nutrients in the farm-made diet supplemented with amino acids was higher than the 
unsupplemented diet. Digestibility of protein was highest in the commercial diets due to 
the extrusion of the diets since extrusion or heat processing in general is known to 
increase digestibility of nutrients. Among the nutrients, the apparent digestibility 
coefficients of lipid were found to be the highest in all the treatments whilst carbohydrate 
was found to be the least.  
 
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In the present study, even though the farm-made diet B had the least yield of 4, 856.00 kg 
ha-1 yr-1, it was about double the productivity of 2, 500 kg ha-1 yr-1 by Ghanaian small-
scale fish farmers (Awity, 2005). This was against the background that the current study 
was carried out in hapas with a stocking density of 2 fish m-2. Hence, under semi-
intensive culture systems commonly practised in earthen ponds in Ghana where fish 
stocking could be up to 4 fish m-2, the performance of diet B could be up to about four 
times the current production levels of small-scale pond fish farmers in the country. 
Further, farmers could increase yield and their profit margin by combining feeding with 
fertilizing. 
 
The use of the farm-made and commercial diets to feed O. niloticus did not result in any 
disease condition in the present study.  All the external and internal organs and structures 
observed in the harvested fish were without any abnormality and the fish were in good 
health and condition. Hence, all the diets used in the present study will be suitable for 
commercial production of O. niloticus. The diets did not have any negative impact on 
water quality. All the measured water quality parameters monitored during the study 
were found to be within acceptable range for tilapia.   
 
The results of the present study have revealed that selection of appropriate ingredients to 
formulate and prepare nutritionally balanced farm-made fish diets is cost effective and 
will boost growth of aquaculture in rural areas where semi-intensive aquaculture is 
mainly practised in Ghana. In the current study, the production cost of a kilogramme of 
the two farm-made fish diets were 1.93 and GHS 2.07 whilst a kilogramme of the two 
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commercial ones were 3.25 and GHS 5.00. In this study, the use of farm-made diets in 
tilapia production was between 23.23 to 135.85 % more profitable than the use of 
commercial diets. The least growth performance of fish fed commercial diet over those 
fed farm-made diet was 5.92 % whilst the highest was 33.71 %. The findings are also in 
agreement with other studies which indicated that local production of fish diets is very 
critical to the development and sustainability of aquaculture in sub-Saharan Africa.  
 
It was more profitable to feed Nile tilapia with farm-made diets not supplemented with 
amino acid and vitamin/mineral premixes than mixing an equal amount of it with Raanan. 
In the present study, the use of the unsupplemented diet gave a higher profit index (1.22) 
than (1.01) when it was mixed with Raanan in a ratio of 1:1. Hence, farmers will make a 
higher profit and cut back on production cost when they use appropriately prepared farm-
made diets than mixing a prepared diet with a commercial one as it was observed during 
the regional survey.  
 
6.2 Recommendations for Research and Policy 
The following recommendations are being made based on the findings of the present 
study: 
6.2.1 Research 
1. A nationwide survey should be conducted to cover all the 10 Regions in the 
country to identify potential fish feed ingredients apart from what are being used 
currently. This should be based on their availability, price and nutritional value.  
 
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158 
 
2. Other alternatives of animal origin with high crude protein levels and relatively 
low cost such as blood, meat and bone meal, offal and other slaughter wastes as 
well as bran of various feed ingredients which are not consumed by humans must 
be given serious consideration.  
 
3. Further research into the possibility for including different kinds of locally 
available feed ingredients preferably those unsuitable for direct human 
consumption so as to meet the growing demand of fish diets for aquaculture 
expansion in the country. 
 
4. Future studies should investigate the nutrient compositions of all commercial fish 
diets available on the Ghanaian market and compare the values with those 
declared by the manufacturers.  
 
5. In the present study, growth trials of the experimental fish were carried out in 
hapas as against the semi-intensive system commonly practised in earthen ponds 
by small-scale fish farmers in Ghana. Hence, similar study should be carried out 
under field conditions in earthen ponds. Under the pond condition the stocking 
density could be increased to 4 fish m-2 as against 2 fish m-2 that was used in this 
study.  
 
6. The growth performance of Nile tilapia should be evaluated when fed with the 
farm-made fish diets in fertilized earthen ponds as well as unfertilized earthen 
ponds.  
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7. The growth performance of Nile tilapia should also be evaluated when fed with 
the farm-made and the commercial fish diets used in the current study to culture 
fish in fish cages. 
 
8. The farm-made fish diets, particularly the one which was not supplemented with 
essential amino acids and vitamin/mineral premix should be processed by heating 
before being fed to Nile tilapia. The diets may also be extruded if possible so as to 
assess their performance. 
 
6.2.2 Policy 
1. As the costs of most of the ingredients used in farm-made fish diets were cheaper 
during the rainy season, farmers should acquire such ingredients in bulk when 
they are in season. Hence, there is an urgent need to improve the storage methods 
employed by feed ingredient dealers, diet manufacturers and farmers so as to 
preserve the nutrient quality and content of ingredients prior to usage and fish 
diets prior to feeding. 
 
2. Fish farmers should cultivate some of the needed ingredients so as to reduce the 
cost of farm-made fish diet production.  
 
3. For fish farmers to produce good quality farm-made fish diets, there should be 
regular training of fish farmers on how to formulate and produce nutritionally 
balanced high quality fish diets.  
 
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4. To increase aquaculture production and make it more attractive to prospective fish 
farmers, the government must assist fish farmers by subsidizing  the cost of 
locally fabricated feed manufacturing machines (particularly extruding and 
pelleting machines) so as to make it affordable to fish farmers.   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Viola, S. (1989). Production of commercial feeds for warm water fish, p. 143-162. In M. 
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APPENDIX I 
INFORMED CONSENT FORM 
STUDY TITLE: Evaluation of Farm-Made and Commonly Used Commercial Fish Diets 
by Small Scale Pond Fish Farmers in Five Selected Regions of Ghana, for Nile Tilapia 
(Oreochromis niloticus L.) 
 
INVESTIGATOR: Francis Assogba Anani  
 
ADDRESS: CSIR-Water Research Institute, ARDEC, Akosombo. P.O. Box AB 139 
Akosombo.  
 
PURPOSE: The survey is to gather information on types of commercial fish feeds used by 
small-scale pond fish farmers in Ghana and fish feed ingredients they use in 
compounding on-farm fish feeds. 
 
DESCRIPTION OF PROCEDURE: If you are willing to participate in this survey, you will 
be asked to provide information on your age, level of education, marital status, average 
monthly income, culture practice, feed and feeding, productivity, production constraints 
and socioeconomic benefits including food security. You don’t need to provide your 
name.  
 
ELIGIBILITY: To qualify for participation, you must be a small-scale (i.e. production 
level of 10 to below 50 metric tons per annum) pond fish farmer. 
 
INCONVENIENCE: You will spend some time to complete the questionnaire. You are not 
compelled to answer the entire questionnaire or to complete the interview. 
 
BENEFITS: The results of the survey will be used to produce cost-effective diets that will 
cut back the production cost of cultured fish and increase profit margin of small-scale fish 
farmers in the country. 
 
CONFIDENTIALITY: Any information you will provide will be kept strictly confidential. 
Your consent form will be kept separate from the data. The data will not be available to 
any other than the researcher. The information may be used in presentations and/or 
research paper. However, your name will never be used in any case. 
 
VOLUNTARY PARTICIPATION: participation in this survey is optional. You will not be 
penalized in any way if you opt out. 
 
QUESTIONS: All your questions about the study are always welcome. For further 
information concerning your participation in this survey, you can contact the principal 
supervisor: Prof. Francis K. E. Nunoo on 0242 981 547 or the principal investigator, 
Francis A. Anani on 0242 139 634. 
 
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VOLUNTEER’S AGREEMENT: The above document describing the importance of the 
study on the commercial fish feeds used by small-scale pond fish farmers in Ghana and 
the feed ingredients they used in compounding on-farm fish feeds has been read and 
explained to me. I have been given the opportunity to ask any questions concerning my 
participation in the survey and answers have been given to my satisfaction. I agree to 
participate as a volunteer.  
 
 
………………………………….                               ……………………………………      
                  DATE                                                                    SIGNATURE/MARK OF VOLUNTEER 
 
 
IF ANY VOLUNTEER CANNOT READ THE FORM, A WITNESS MUST SIGN HERE: 
 
I was present when the importance of the survey was read to the volunteer. All questions 
were answered and the volunteer agreed to take part in the study.  
 
 
………………………………….                               …………………………………… 
                   DATE                                                                              SIGNATURE OF WITNESS 
 
 
 
I certify that the nature and purpose of the potential benefits and the inconvenience 
associated with participating in this survey has been explained to the above individual. 
 
 
 
………………………………….        …………………………………………......... 
                       DATE                                  SIGNATURE OF PERSON WHO OBTAINED CONSENT 
 
 
 
 
 
 
 
 
 
 
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APPENDIX II 
Fish Feeds and Feed Ingredients Survey 
Department of Marine and Fisheries Sciences, UG, Legon 
 
The purposes of this survey are to gather the following information: 
1. Types of commercial fish feeds used by small-scale pond fish farmers in Ghana; 
2. Fish feed ingredients used by small-scale pond fish farmers in compounding on-
farm fish feeds in Ghana. 
The results of the survey will be used to produce cost-effective diets that will cut back the 
production cost of cultured fish and increase profit margin of small-scale fish farmers in 
the country. 
Please, take some time to complete this questionnaire. 
 
 
 
Questionnaire Identification Code (     )                           
Date…….……………………………….                           
 
 
 
 
 
 
 
 
 
 
 
 
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I. LOCATION 
1. Region: …………………………………………………………………………………. 
2. District: …………………………………………………………………………………. 
3. Name of Village/Locality: ……………………………………………………………… 
 
II. BIO-DATA 
4. Gender:…………………………………………………………………………………. 
5. Age:……………………………………………………………………………………… 
6. Educational level:………………………………………………………………………...                                                                            
 
III. LIVELIHOOD/HOUSEHOLD 
7. Are you married?                           Yes                                     No   
8. How many spouses do you have? ………………………………………………………. 
 9. How many children do you have? ……………………………………………………...  
10. Do you have any other occupation(s) aside from fish farming?      Yes                   No   
11. If Yes, state it/them…………………………………………………………………….. 
12. Does your household have the following?        (Tick appropriate boxes)   
      i. Electricity                           ii. Fixed phone (line)                      iii. Television                
      iv. Fridge                               v. Radio                                           vi. Computer                
      vii.  Internet connection (of any sort)                                            viii. Mobile phone                                                                                                                                                                                                                                   
13. What is your average monthly income?........................................................................... 
 
IV. CULTURE PRACTICE 
14. Which of these culture practices do you engage in?      (Tick the appropriate box)   
 i. Extensive                                    ii. Intensive                     iii. Semi-intensive                              
15. Do you use fertilizer in your ponds?       Yes                                No  
16. If Yes, why?..................................................................................................................... 
17. If Yes, what type? ……………………………………………………………………... 
18. If No, why?...................................................................................................................... 
19. Do you feed your fish every day?           Yes                                 No 
20. If No, which days you don’t feed them and why? …...................................................... 
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21. How many times do you feed your fish in a day? …………………………………….. 
22. What quantity of feed do you give the fish per day?....................................................... 
23. How do you determine this?............................................................................................ 
 
V. PRODUCTIVITY 
24. What type(s) of fish do you culture? …………………………………………………. 
25. Why do you culture this/those type(s) of fish? ……………………………………….. 
26. How many ponds do you have?....................................................................................... 
27. What are the sizes of your smallest and largest ponds and the number and type of fish 
       you put in each 
Type of pond Size  Types of fish No. of fish 
Smallest    
Largest    
 
28. Where do you obtain your fingerlings from? ……………………………………….. 
29. If you produce your own fingerlings, where do you obtain your brood stocks (parent 
fish) from?............................................................................................................................ 
30. Is/Are your source(s) of fingerling supply reliable?   Yes                       No  
31. If No, why?...................................................................................................................... 
32. What average size (g) of fingerlings do you stock?......................................................... 
33. At what size (g) do you harvest the stocked fish?........................................................... 
34. Why do you harvest the fish at that size? ……………………………………………. 
35. How long does it take for the stocked fish to reach the size at harvest? ……………… 
36. What is your average annual production level in metric tons?........................................ 
 
VI. PRODUCTION CONSTRAINTS 
37. What are the challenges (difficulties) you are facing as a pond fish farmers? 
i. ……………………………………………..      ii. ……………………………………… 
iii…………………………………………….       Iii………………………………………     
38. Do you think you have sufficient knowledge in fish farming?   Yes                    No 
39. If Yes, how did you acquire the knowledge?  (Tick the appropriate box) 
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       Apprenticeship                                  Expert training    
       On the job experience                       Formal education/training  
 
VII. FISH FEEDS 
40. Do you use commercial or on-farm produced fish feeds or both? …………………… 
      If you only produce your own feeds, skip to 48 
41. If you use commercial feed(s) then provide the following: 
 Brand name Price (GH¢)/CP (%) Wt. (kg) per bag  
i.    
ii.    
iii.    
iv.    
v.    
 
42. Why do you use this/these brand(s) of feed(s)?............................................................... 
43. State the crude protein (CP) levels of the commercial feeds you use and the categories 
of fish you feed these with: 
 CP of Feed Used Category of Fish Fed (i.e. fry, fingerlings, Juveniles, table-sized, brood stocks) 
i.   
ii.   
iii.   
iv.   
 
44. Which of these factors do you consider when buying commercial fish feeds?     
       (Tick appropriate boxes)                          i. Ingredients used     
    ii. Cost                                                         iii. Expiry date           
   iv. Others (specify)…………………………….……………………………….. ……… 
45. Why do you use commercial feeds instead of producing your own fish feeds? 
     (Tick appropriate boxes)                          i. You do not know how  
    ii. Lack of machinery/equipment              iii. Non-availability of necessary ingredients           
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   iv. Others (specify)…………………………….……………………………….. ……… 
46. Do you wish to produce your own fish feeds in the future?  Yes             No              
47. If No, why? ……………………………………………………………………………. 
      Skip to 66 
48. Why do you produce your own feed?.............................................................................. 
49. Have you had any training in fish feed formulation and production?    Yes              No                                 
50. If Yes, where did you have the training?  (Tick the appropriate box) 
       Apprenticeship                                  Expert training    
       On the job experience                       Formal education/training  
51. Which ingredients do you use to produce your feed? 
   i………………………………………..              ii ……………………………………… 
   iii………………………………………             iv……………………………………… 
   v……………………………………… .            vi............................................................. 
52. Where do you obtain your ingredients from and how much does a bag of each go for? 
 Ingredient Source Price per bag 
(GH¢) 
Net Weight 
(kg) 
i.     
ii.     
iii.     
iv.     
v.     
vi.     
 
 
53. Do you have any knowledge on anti-nutritional factors (ANFs) in feed ingredients? 
                                 Yes                               No  
54. Do you use any additives/attractants in your feeds?    Yes                                      No  
55. If Yes, why?..................................................................................................................... 
56. If Yes, name them: 
      i……………………………………………..    ii……………………………………… 
     iii…………………………………………….    iv……………………………………... 
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57. What are the crude protein (CP) levels of feeds you produce and the corresponding  
       categories of fish you feed each type with? 
 CP of Feed Used Category of Fish Fed (i.e. fry, fingerlings, Juveniles, table-sized, brood stock) 
i.   
ii.   
iii.   
iv.   
v.   
 
58. What are the factor(s) that influence your choice of ingredients used in feed    
       production?  
    (Tick as many boxes as appropriate)     
  i. Affordability                                ii. Availability                               iii. Cost                                                                                                                                                     
  iv. Nutrient composition                 v. Seasonality                                                                              
  vi. Others (Specify)………………………………………………………………………  
59. Do you Process your ingredient(s) in any way before usage?   Yes               No   
60. If Yes, by what means?      (Tick as many boxes as appropriate)     
    i. Boiling                  ii. Roasting                    iii. Steaming              iv. Milling          
    v. Others? (Specify) …………………………………………………………………… 
61. Do you run any chemical analysis on the ingredients used?  Yes                    No   
62. Name the equipment/tools you use in producing the feed(s) 
 
 Equipment/Tool What it’s used for 
i.   
ii.   
iii.   
iv.   
v.   
 
63. How do you store the feed you produce? ……………………………………………… 
64. Do the fish eat the feed you produce easily?................................................................... 
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65. Do your fish perform well on the feed you give them? 
                          Yes       No      
66. Are you available to be contacted for further information to advance the purposes of 
this study?          Yes                           No 
67. If Yes, kindly provide the following: 
i. Name:……………………………………………………………………………. 
ii. Phone Number:…………………………………………………………………... 
iii. E-mail:…………………………………………………………………………… 
68. COMMENTS:………………………………………………………………………….. 
……………………………………………………………………………………………… 
……………………………………………………………………………………………… 
……………………………………………………………………………………………… 
 ………………..……………………………………………………………………………. 
……………………………………………………………………………………………… 
                         
THANK YOU FOR YOUR TIME AND COOPERATION     
Francis A. Anani 
Researcher 
 
 
 
 
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APPENDIX III 
 
Mean living weight (±SD) for each treatment during growth trials 
Week Diet A (g) Diet B (g) Coppens (g) Raanan (g) Diet E (g) 
Initial 23.0 ± 2.0 23.2 ± 1.9 22.7 ± 1.9 22.6 ± 2.3 22.5 ± 2.2  
Second 33.1 ± 3.8 33.0 ± 4.4 32.7 ± 3.9 32.3 ± 3.2 31.9 ± 4.0 
Fourth  48.1 ± 6.0 48.9 ± 7.0 46.1 ± 7.0 46.6 ± 5.2 46.4 ± 6.2 
Sixth 56.7 ± 7.6 59.0 ± 9.1 54.6 ± 8.9 55.7 ± 6.4 55.8 ± 8.0 
Eighth  64.5 ± 9.1  66.3 ± 11.6 68.5 ± 13.8 67.1 ± 9.9 63.7 ± 11.1 
Tenth 77.7 ± 11.6 80.1 ± 14.8 87.1 ± 17.1 87.6 ± 14.0 78.8 ± 13.9 
Twelfth  94.1 ± 14.6 95.9 ± 17.0 107.9 ± 18.8 114.0 ± 19.2 97.8 ± 17.0 
Fourteenth  106.8 ± 15.3  106.3 ± 18.7 120.0 ± 20.0 138.1 ± 25.3 110.1 ± 19.2 
Sixteenth  115.7 ± 16.7 114.8 ± 20.17 128.9 ± 20.9 157.7 ± 29.8 121.3 ± 21.7 
Eighteenth  129.1 ± 19.2 125.2 ± 21.8 139.8 ± 24.0 176.1 ± 36.3  133.8 ± 27.1 
Twentieth  140.3 ± 23.4 131.0 ± 24.4 148.3 ± 25.4  187.6 ± 42.1 140.7 ± 28.5 
 
 
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APPENDIX IV 
 
Detailed Water Quality Parameter range for the various dietary treatments and open pond waters during growth trials 
 Diet A  Diet B  Coppens  Raanan  Diet E  Open Pond  
Temperature (oC) 27.58-29.83  27.66-29.78 27.71-29.76 27.72-29.76 27.69-29.82 27.76-29.82 
Dissolved Oxygen (mgL-1) 1.15-3.30 1.29-3.08 1.38-3.10 1.48-2.90 1.55-3.03 1.56-2.95 
Salinity (ppt) 0.03-0.04 0.03-0.04 0.03-0.04 0.03-0.04 0.03-0.04 0.03-0.04 
Ph 5.79-7.62  6.03-6.95 6.00-6.88 6.00-6.58 6.03-6.66 6.12-6.58 
Phosphate (mgL-1) 0.10-0.67  0.12-2.55 0.09-0.58 0.10-0.58 0.11-1.09 0.10-0.40 
Nitrate (mgL-1) 0.40-6.10 0.40-3.20 0.40-5.60 0.40-6.60 0.60-3.70 0.50-1.80 
Nitrite (mgL-1) 0.001- 0.086   0.001-0.040 0.002-0.111 0.001-0.113 0.002-0.012 0.003-0.007 
Ammonia (mgL-1) 0.07-0.50  0.11-0.51 0.10-0.52 0.10-0.50 0.08-0.49 0.16-0.49 
Alkalinity (mgL-1) 55.0-68.5 53.0-69.0 54.5-73.0 54.5-67.5 52.0-66.0 57.0-68.0 
Total Suspended solids (ppt) 21-70  22-75 22-61 22-60 18-70 20-85 
Total Hardness (mgL-1) 2.42-3.81  2.48-4.33 2.95-4.98 2.61-4.74 2.05-4.84 2.49-4.60 
 
 
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