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EFFECT OF DIETARY FIBRE LEVELS AND PARTICLE SIZE ON BROILER 
PERFORMANCE, GUT MORPHOGENESIS AND IMMUNE STATUS 
 
 
BY 
HENNEH EUNICE AGYEI 
(10488974) 
 
 
A THESIS SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES IN PARTIAL 
FULFILLMENT OF THE AWARD OF THE DEGREE OF MASTER OF PHYSIOLOGY 
IN ANIMAL SCIENCE 
 
 
DEPARTMENT OF ANIMAL SCIENCE 
 
 
DECEMBER, 2020  
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ABSTRACT 
The study investigated the effect of increasing dietary fibre levels and varying maize particle size 
on nutrient digestibility, growth performance, gut morphogenesis and immune status of broilers. 
Three hundred Cobb 500 broiler chicks were randomly allocated to six dietary treatments in a 2 X 
3 factorial arrangement (two maize particle sizes and three levels of wheat bran inclusion). Each 
treatment was replicated five times with ten broilers per replicate and the trial lasted for 49 days. 
Treatments 1 (T1), 2 (T2; control diet) and 3 (T3) contained fine maize particles with treatments 
4 (T4), 5 (T5) and 6 (T6) containing coarse maize particles. Birds on T1 and T4, T2 and T5, and 
T3 and T6 were fed 6, 8 and 10% wheat bran respectively from day one to 21. Wheat bran inclusion 
from day 22 to 42 increased to 13, 15 and 17% for birds on T1 and T4, T2 and T5, and T3 and T6 
respectively. There were no significant differences (p≥0.05) in nutrient digestibility among 
treatments. Overall, average daily feed intake increased for broilers on T4 (107.15g) with no 
dietary treatment effect being observed on average daily gain and final body weight. However, 
broilers fed coarse maize particles were the most efficient in converting feed to gain. The relative 
empty gizzard weight of broilers fed coarse maize particles was significantly higher (p≤0.05) than 
that of broilers fed fine maize particles. No significant differences (p≥0.05) were observed in 
relative carcass weights, caecal short-chain fatty acid concentrations, haematological indices and 
serum glucose content. Averagely, concentration of acetic acid in the caecum (8147.14 µg/g) was 
the highest compared with the other short-chain fatty acids. Results of this study indicate that birds 
can tolerate diets containing up to 17% (finisher phase) WB with fine or coarse maize particles 
without any adverse effect on growth, gut health and immune status. Feed manufacturers can 
include up to 17% WB (finisher phase) with fine or coarse particles in broiler diets in order to cut 
down feed cost with no adverse effect on broiler performance and gut health.
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DEDICATION 
I dedicate this work to the blessed memory of my gifted mentor, Dr. Thomas N. N. Nortey, 
Senior lecturer, Department of Animal Science, School of Agriculture, College of Basic and 
Applied Sciences, University of Ghana for sowing in me seeds of academic and lifetime 
excellence. With God’s grace, I will surely make these seeds blossom. God richly bless you 
and your family. 
In addition, I dedicate this work to my outstanding parents, Mr and Mrs Agyei Henneh for your 
relentless love, sacrifices, guidance and readiness to always make life and schooling 
comfortable for me. Your amazing roles in this extraordinary journey is a memorial to me to 
strive harder to do more with what I have. God richly bless you and your efforts. 
 
  
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ACKNOWLEDGMENT 
My unrivalled praise, honour and greatest appreciation go to the Lord God Almighty, for His 
love, grace, mercies and immense provision which have seen me through this study. By His 
grace, all hurdles and obstacles were surmounted with timeless lessons been learnt. Thank you 
Lord. 
I am highly indebted to my well-abled mentor and past principal supervisor of blessed memory, 
Dr. Thomas N. N. Nortey, Senior lecturer, Department of Animal Science, University of 
Ghana, for his vote of confidence, foresightedness concerning this research work and pushing 
me even in my course work. Your invisible strength, encouragement and discipline truly 
spurred me on in completing this work. May our dear Lord Almighty bless you and your caring 
family.  
Also, I am extremely grateful to my principal supervisor, Dr. Leonard K. Adjorlolo, Senior 
Research Fellow, Department of Animal Science, University of Ghana, for taking me on as his 
student at a very short notice. Your encouragement and coaching helped shape this research 
work into a meaningful one. Again, I am very grateful to Dr. James E. Futse, my co-supervisor 
and Senior lecturer, Department of Animal Science, University of Ghana, for his counsel in 
putting this work together. God bless them. I am also thankful to all lecturers at the Department 
of Animal Science, University of Ghana. God bless you; your work is very much appreciated. 
To my parents, Mr and Mrs Agyei Henneh, your love, unrelenting support, and counsel during 
this work is what every student needs. Thank you for all your prayers and care which covered 
me. God bless you both. To my siblings and entire family, you shared in my joys and lows 
during this journey and covered me materially and prayerfully. I am enormously grateful to 
you all. 
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My deepest appreciation goes to Mr Henry Nortey, Miss Bernadette Nortey, Miss Doris Nortey 
and the entire Nortey family for your love, prayers, motivation and assistance in all aspects. 
May my gratitude for your lives be a reason for God to keep showing you everlasting kindness. 
Also, my gratitude goes to the A.G. Leventis Foundation Scholarship Scheme of the College 
of Basic and Applied Sciences, for their financial support towards this work. Likewise, I am 
thankful to Assisting Management in the Poultry and Layer Industries, AMPLIFIES-Ghana, 
for their logistical support. I am very thankful to Dr. Frank Idan for aiding me in my data 
analysis. God bless you for all your counsel.  
I am especially indebted to Mr Kenneth Aweye and Mr Titus Kale for their graceful support 
during my field work and thereafter. Indeed you made the research work enjoyable, God richly 
bless you. To all the staff of Livestock and Poultry Research Centre (LIPREC), especially my 
family at the Feed mill and Slaughter house, I am extremely grateful for your support and 
motivation. God richly bless you.  
To the staff at the Nutrition and Microbiology laboratories and entire departmental staff of 
Animal Science, God bless you for aiding in the success of this work. To my fellow students 
at the Nutrition laboratory, thank you for supporting me with your care and prayers. My fellow 
graduate students of Animal Science, I appreciate all you did. God bless you. 
Last but not least, to Miss Rose Owusu-Bremang, it has been a journey but we made it by 
God’s grace working through our loved ones. Thank you for all the moments and God bless 
you.  
 
  
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TABLE OF CONTENTS 
DEDICATION .......................................................................................................................... iv 
ACKNOWLEDGMENT............................................................................................................ v 
LIST OF TABLES .................................................................................................................... xi 
LIST OF PLATES ................................................................................................................... xii 
LIST OF TABLES .................................................................................................................. xiii 
CHAPTER ONE ........................................................................................................................ 1 
INTRODUCTION ......................................................................................................................... 1 
1.1. Hypothesis ......................................................................................................................... 4 
1.2. Objectives .......................................................................................................................... 4 
CHAPTER TWO ....................................................................................................................... 5 
LITERATURE REVIEW .......................................................................................................... 5 
2.1. The Ghanaian poultry industry ................................................................................................ 5 
2.2. The Impact of Feed Formulation on Broiler Growth and Feed Cost ......................................... 6 
2.3. Dietary Fibre........................................................................................................................... 7 
2.3.1. Types of dietary fibre ........................................................................................................... 8 
2.3.1a. Oligosaccharides ............................................................................................................ 8 
2.3.1b. Analogous carbohydrates - Resistant starch (RS) ............................................................ 9 
2.3.1c. Lignin .......................................................................................................................... 10 
2.3.1d. Non-Starch Polysaccharides (NSP) ............................................................................... 10 
2.3.1d.1. Cellulose ................................................................................................................... 11 
2.3.1d.2. Non-cellulosic NSPs .................................................................................................. 11 
2.3.1d.3. Pectins....................................................................................................................... 12 
2.3.2. Classification of Dietary fibre ............................................................................................ 13 
2.3.2a. Classification based on solubility and viscosity of dietary fibre ..................................... 13 
2.3.2a.1. Soluble Dietary fibres (SDF) ...................................................................................... 14 
2.3.2a.2. Insoluble fibres (IDF) ................................................................................................ 15 
2.3.2b. Classification based on Fermentability .......................................................................... 15 
2.3.3. The Role of Dietary Fibre in Monogastric Nutrition ........................................................... 16 
2.3.3a. Effect of Dietary Fibre on Voluntary Feed Intake .......................................................... 18 
2.3.3b. Effect of Dietary Fibre on Nutrient Digestibility ........................................................... 18 
2.3.4. The Gut Microbiota and Dietary Fibre Fermentability in Poultry ........................................ 20 
2.3.4a. End products of Dietary Fibre Fermentation ................................................................. 22 
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2.3.5. Dietary Fibre as a Potential Prebiotic in Poultry Nutrition................................................... 23 
2.3.5a. Effect of Dietary Fibre on the Production of Short Chain Fatty Acids (SCFAs) ............. 28 
2.4. Particle Size .......................................................................................................................... 31 
2.4.1. Importance of Dietary Particle Size in Poultry Nutrition ................................................. 31 
2.4.1a. Factors that Influence Dietary Particle Size in Poultry Nutrition .................................... 32 
2.4.1b. Effect of Grinding on Feed Utilisation in Poultry Nutrition ........................................... 33 
2.4.2. Effect of Dietary Particle Size on Growth Performance .................................................. 34 
2.4.3. Effect of Dietary Particle Size on Microbial Profile ............................................................ 36 
2.4.4. Effect of Dietary Particle Size on the Production of SCFAs ................................................ 37 
2.4.4a. Impact of Short-Chain Fatty Acids on Nutrient Utilization and Digestibility ..................... 38 
2.4.4b. Impact of Short-Chain Fatty Acids on Gut Morphology .................................................... 39 
2.5. Wheat bran as a dietary fibre source ...................................................................................... 41 
2.5a. Influence of Particle Size and Wheat Bran on Butyric Acid Production ............................ 41 
2.6. Nutritional immune modulation as an alternative to antibiotic usage in broiler production ..... 43 
2.7. Haematological response of broilers to wheat bran as a dietary fibre source in broiler diets ... 45 
2.7.1. Blood haematological indices and what they imply ......................................................... 45 
CHAPTER THREE ................................................................................................................. 48 
MATERIALS AND METHODS ............................................................................................. 48 
3.1. Experimental Site.................................................................................................................. 48 
3.2. Particle Size Analysis ........................................................................................................... 48 
3.3. Maize Particle Size Distribution ............................................................................................ 51 
3.4. Experimental Diets ............................................................................................................... 52 
3.5. Experimental Birds, Experimental Design and Housing ......................................................... 53 
3.6. Management of Experimental Birds ...................................................................................... 55 
3.7. Data Collection ..................................................................................................................... 57 
3.7.1. Growth Trial .................................................................................................................. 57 
3.7.2. Carcass Characteristics Analysis and Caecal pH Measurement ....................................... 58 
3.7.3. Blood Sampling ............................................................................................................. 58 
3.7.3.1. Determination of Haematological Indices .................................................................... 59 
3.7.3.2. Differential White Cell Count ...................................................................................... 59 
3.7.3.3. Serum Glucose Determination ..................................................................................... 59 
3.7.4. Gut morphological analysis ............................................................................................ 60 
3.7.5. Analysis of Caecal Short-Chain Fatty Acids Concentrations ........................................... 61 
3.7.6. Microbial Population ...................................................................................................... 62 
3.7.7. Apparent Nutrient Digestibility Trial .............................................................................. 63 
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3.8. Economics of Production ...................................................................................................... 63 
3.9. Chemical Analysis ................................................................................................................ 64 
3.10. Statistical Analysis .............................................................................................................. 64 
CHAPTER FOUR .................................................................................................................... 66 
RESULTS ................................................................................................................................ 66 
4.1. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Mortality ..................................................................................................................................... 66 
4.2. Effect of dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Apparent Nutrient Digestibility .................................................................................................... 66 
4.3. Effect of dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Overall Growth Performance (day one to day 42) ........................................................................ 66 
4.4.1. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Growth Performance during the Starter Phase (day one to day 21) ............................................... 70 
4.4.2. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Growth Performance during the Finisher Phase (day 22 to day 42) ............................................... 72 
4.5. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Relative Weights of Carcass Parameters ...................................................................................... 73 
4.6. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Relative Organ Weights ............................................................................................................... 74 
4.7. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Caecal Short-Chain Fatty Acids Profile and Concentration (SCFAs) ............................................ 74 
4.8. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Caecal pH and Microbial Count ................................................................................................... 78 
4.9. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Intestinal Morphometric Measurements ....................................................................................... 80 
4.10. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Blood Haematological Indices and Serum Glucose ...................................................................... 82 
4.11. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Immune Status ............................................................................................................................. 83 
4.12. Economics of Production .................................................................................................... 85 
DISCUSSION .......................................................................................................................... 86 
5.1. Percentage mortality ............................................................................................................. 86 
5.2. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Apparent Nutrient Digestibility .................................................................................................... 87 
5.3. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Overall Growth Performance (day one to day 42) ........................................................................ 88 
5.5. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Growth Performance during the Finisher Phase (day 22 to day 42) ............................................... 92 
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5.7. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Relative Organ Weights ............................................................................................................... 94 
5.8. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Caecal Short-Chain Fatty Acids (SCFAs) Profile, pH and Microbial Population........................... 96 
5.9. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on the 
Jejunal and Ileal Morphology ....................................................................................................... 98 
5.10. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size Blood 
Haematological Indices and Serum Glucose ................................................................................. 99 
5.11. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size on 
Immune Status ........................................................................................................................... 101 
CHAPTER SIX ...................................................................................................................... 103 
CONCLUSIONS AND RECOMMENDATIONS ................................................................ 103 
6.1. Conclusions ........................................................................................................................ 103 
6.2. Recommendations ............................................................................................................... 104 
REFERENCES ...................................................................................................................... 106 
 
 
 
 
 
  
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LIST OF TABLES 
 
Figure 2. 1: Components of carbohydrates (Dai and Chau, 2017) ............................................ 7 
Figure 2. 2: Components of dietary fibre (Dhingra et al., 2021) ............................................... 9 
Figure 2. 3: Classification of non–starch polysaccharides (Choct, 2015) ............................... 11 
Figure 2. 4: Classification of dietary fibre based on fermentability (Papanikou, 2016) .......... 16 
Figure 2. 5: Dietary fibre fermentation end products (Lindberg, 2014) .................................. 23 
Figure 2. 6: Mechanisms by which dietary fibre & SCFAs work as a prebiotic (Pourabedin 
and Zhao, 2015) ....................................................................................................................... 27 
Figure 2. 7: Effect of particle size on nutrient digestion, growth and gut health in poultry 
(Kheravii et al., 2018) .............................................................................................................. 36 
Figure 2. 8: Effect of SCFAs on gut morphology (Scheppach, 1994) ..................................... 40 
Figure 3. 1: Particle size distribution of maize ground using a 6mm screen ........................... 51 
Figure 3. 2: Particle size distribution of maize ground using an 8mm screen ......................... 52 
Figure 4. 1: Trends in average daily feed intake ...................................................................... 69 
Figure 4. 2: Trends in average daily gain ................................................................................ 69 
Figure 4. 3: Trends in feed conversion ratio ............................................................................ 70 
Figure 4. 4: Propionic acid concentration in caecal content .................................................... 76 
Figure 4. 5: Acetic acid concentration in caecal content ......................................................... 76 
Figure 4. 6: Butyric acid concentration in caecal content ........................................................ 77 
Figure 4. 7: Caecal pH values .................................................................................................. 78 
Figure 4. 8: Interactive effect of dietary fibre level (using wheat Bran as a DF source) and 
maize particle size on caecal microbial count .......................................................................... 79 
  
  
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LIST OF PLATES 
Plate 3. 1: Screens used in the milling of maize ...................................................................... 49 
Plate 3. 2: A Rotap machine with 7 sieves ............................................................................... 49 
Plate 3. 3: Brooding period ...................................................................................................... 56 
Plate 4. 1: Histopathogical images of the jejunal segments of birds on dietary treatments ..... 81 
Plate 4. 2: Histopathogical images of the ileal segments of birds on dietary treatments ......... 82 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
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LIST OF TABLES 
Table 2. 1: Examples of non-cellulosic NSPs, their properties and food sources ................... 12 
Table 2. 2: Nutrient composition of some common cereal grains and co-products (g/kg 
DM) .......................................................................................................................................... 17 
Table 2. 3: Chemical composition of wheat bran .................................................................... 42 
Table 3. 1: Sieve and sieve agitator (s) arrangement ............................................................... 50 
Table 3. 2: Experimental diets ................................................................................................. 53 
Table 3. 3: Percentage composition of the dietary treatments fed during the starter phase (day 
one to day 21)........................................................................................................................... 54 
Table 3. 4: Percentage composition dietary treatments fed during the finisher phase (day 22 to 
day 42) ..................................................................................................................................... 55 
Table 3. 5: Gradient time program for HPLC analysis ............................................................ 62 
Table 3. 6: Cost of feed ingredients on a per kilogram basis ................................................... 64 
Table 4. 1:Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle 
size on dry matter, organic matter and crude protein digestibility .......................................... 67 
Table 4. 2: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle 
size on overall growth performance (day 1 to day 42) ............................................................ 68 
Table 4. 3: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle 
size on growth performance during the starter phase (day 1 to day 21) .................................. 71 
Table 4. 4: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle 
size on growth performance during the finisher phase (day 22 to day 42) .............................. 72 
Table 4. 5: Effect of dietary fibre level (using wheat Bran as a DF source)  and maize particle 
size on relative weights of carcass parameters ........................................................................ 73 
Table 4. 6: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle 
size on relative organ weights .................................................................................................. 75 
Table 4. 7: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle 
size on caecal short-chain fatty acids concentration ................................................................ 77 
Table 4. 8: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle 
size on caecal pH and microbial population ............................................................................ 79 
Table 4. 9: Effect of dietary fibre level (using wheat Bran as a DF source)  and maize particle 
size on morphology of the jejunum and ileum ......................................................................... 80 
Table 4. 10: : Effect of dietary fibre level (using wheat Bran as a DF source)  and maize particle 
size on blood haematology and glucose levels ........................................................................ 83 
Table 4. 11: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle 
size on white blood cell differentials and immune relative organ weight (expressed as a 
percentage of live weight) ........................................................................................................ 84 
Table 4. 12: Cost of feed per kilogram of dietary treatments (GHȼ) ....................................... 85 
Table 4. 13: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle 
size on feed cost variables (GHȼ) ............................................................................................ 85 
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LIST OF ABBREVIATIONS 
  
     
 AA Acetic Acid 
    
ADFI Average Daily Feed Intake 
    
ADG Average Daily Gain 
    
AFI Alternative Feed Ingredients 
    
ANF Anti-Nutritional Factor 
     
BA Butyric Acid 
     
BW Body Weight  
     
CD Crypt Depth 
     
CF Crude Fibre 
     
CP Crude Protein 
   
DDGS Dried Distillers Grains with Solubles 
     
DF Dietary Fibre 
     
DM Dry Matter 
     
EE Ether Extract 
    
FOS Fructo-Oligosaccharides 
    
GIT Gastro-Intestinal Tract 
    
GOS Galacto-oligosaccharides 
    
GSD Geometric Standard Diameter 
     
HCL Hydrochloric Acid 
     
HCT Haematocrit 
     
HGB Haemoglobin 
 
HPLC High-Performance Liquid Chromatography-Ultraviolet Detection 
  
MCH Mean Corpuscular Haemoglobin 
  
MCHC Mean Corpuscular Haemoglobin Concentration 
     
MCV Mean Cell Volume 
    
MOS Mannan-Oligosaccharides 
   
NCP Non-Cellulosic Polysaccharides 
    
NFE Nitrogen Free Extracts 
    
NSP Non-Starch Polysaccharides 
     
OM Organic Matter 
     
PA Propionic Acid 
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PCV Packed Cell Volume 
     
RBC Red Blood Cell 
     
RS Resistant Starch 
    
SCFA Short-Chain Fatty Acids 
   
SDF Soluble Dietary Fibre 
   
TNSP Total Non-Starch Polysaccharides 
    
TOS Total Oligosaccharides 
   
VFA Volatile Fatty Acids 
      
VH Villi Height 
     
WB Wheat Bran 
     
WBC White Blood Cell 
 
  
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CHAPTER ONE 
INTRODUCTION 
Poultry meat and their associated products are the leading protein choice in human nutrition 
internationally (Mottet and Tempo, 2017). Consequently, in most developing countries, the poultry 
sub-sector is one of the fastest growing sectors in the agricultural industry (Adeyonu et al., 2021). 
This rapid growth is attributed to factors such as urbanization, continuous rise in global population 
and increase in purchasing power (Borda-Molina et al., 2018). For instance, about 130 million tons 
of chicken was projected to be produced globally in 2020 to match the demands of the growing 
world population (FA0, 2020). Again, according to Alexandratos and Bruinsma (2012), the 
production of poultry meat will increase by 121% by 2050 in order to prevent food scarcity. 
Additionally, Mottet and Tempio (2017) stated that, the comparative ease in the day-to-day 
management of poultry also makes it a preferred enterprise by smallholder farmers.  
Researchers are constantly searching for intervening measures to increase production efficiency 
while maximizing profit (Yegani and Korver, 2008). These intervening measures such as increased 
broiler growth rates and feed efficiency are essential as they can potentially offset some of the 60–
70% feed cost (Cooper and Songer, 2009). However, these advances made in growth rates and 
feed efficiency of broilers have made maintaining their health status very demanding (Cooper et 
al., 2013). This is due to the possible increase in the incidence of diseases and infections, which 
can lead to the loss of profit. Several studies have indicated the maintenance of the gut 
(gastrointestinal tract, GIT) ecosystem as an effective way of enhancing broiler health and optimal 
performance (Thursby and Juge, 2017; Jha et al., 2019). The gut is responsible for digestion and 
absorption of nutrients, pathogen destruction and immune system development (Dittoe et al., 
2018). Traditionally, the inclusion of antibiotics in broiler diets helped maintain the gut ecosystem 
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(Huyghebaert et al., 2011). However, incidence of microbial resistance and antibiotic residues in 
chicken have been associated with the long-term use of antibiotics in animals (Mathew et al., 
2007). The inclusion of feed ingredients which have the ability to create a favourable environment 
for the growth of beneficial bacteria while maintaining gut integrity and health has been 
recommended as an alternative nutritional strategy to the use of antibiotics (Rinttilä and Apajalahti, 
2013; Borda-Molina et al., 2018). This implies that, the objective of feed formulation must be 
geared towards enabling broilers achieve their optimum growth performance while boosting gut 
health (Ghaffari et al., 2007).  
Currently, the concept of alternative feed ingredients (AFIs) inclusion in broiler feed has been 
largely considered as a way to reduce broiler production cost, boost gut health while maximizing 
optimum growth and profit (Nortey et al., 2013). This is because these AFIs are readily available, 
less costly and are not consumed by humans. Agro-industrial/feed processing by-products such as 
wheat bran, cassava root meal, cocoa pod husks, corn cobs and sorghum barley brewer’s spent 
grain are examples of AFIs (Nortey et al., 2013; Nortey et al., 2015). The use of agro-
industrial/feed processing ingredients partially in feed manufacture for broilers is widely practiced 
by Ghanaian smallholder and rural broiler farmers in order to reduce feed cost. Also, feed 
manufacturing companies are gradually embracing the use of AFIs (groundnut cake, palm kernel 
cake and fish meal) as replacements for major broiler feed ingredients (soybean meal, wheat and 
maize (5m editor, 2011). However, these AFIs are high in dietary fibre (DF). This limits their 
inclusion in broiler diets due to the absence of endogenous enzymes in broilers (Jha et al., 2019). 
Traditionally, all broiler diets contain an amount of DF due to the grains and legume-based feed 
ingredients used in broiler diets (Mateos et al., 2012). As such, commercial feed mills produce 
diets with about three percent crude fibre content (Mateos et al., 2012). 
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Dietary fibre is the indigestible portion in the cell walls of plant carbohydrates such as cereals, 
legumes and agro-industrial/feed processing by-products (Tiwari and Jha, 2017). Recent studies 
have shown the positive effects dietary fibre (DF) has on promoting optimum growth performance 
and gut health (Chawla and Patil, 2010; Jha and Berrocoso, 2016; Tiwari and Jha, 2017). In the 
area of gut health, microbial fermentation of dietary fibre (such as wheat bran) promotes high 
antioxidant activities, selective growth of beneficial bacteria (Bifidobacteria and Lactobacillus 
spp.) and the production of short-chain fatty acids (SCFAs) such as butyrate (Ahsan et al., 2016; 
Iseri, 2017). Butyrate inhibits the occurrence of gut disorders such as diarrhoea and coccidiosis, 
increases villi height, villi height to crypt depth ratio and promotes overall broiler growth 
performance (Bedford and Gong, 2018). On the other hand, dietary fibre is described as an anti-
nutritive factor (ANF) due to the negative effects it exerts nutrient utilization and voluntary feed 
intake (Jha et al., 2019) in monogastrics. However, these effects are largely influenced by fibre 
type, feed form and physiochemical properties (Jha and Berrocoso, 2016).  
According to Adibmoradi et al. (2016) and Zaefarian et al. (2016), manipulation of the ingredient 
particle size can help improve upon these negative effects of dietary fibre. Optimum growth 
performance has been associated with the inclusion of structural components such as coarse 
particles or whole grains of maize in monogastric diets (Xu et al., 2015a, Kheravii et al., 2018). 
Jiménez-Moreno et al. (2013) showed that, the development of digestive organs such as the 
gizzard, crop and proventriculus and overall gut development was enhanced by the inclusion of 
coarse feed particles in broiler diets. The development of these organs enhances nutrient 
digestibility through an increase in enzymatic activities and reverse contractions (Svihus, 2014). 
This results in an increase in feed efficiency and growth. There is the need to explore the 
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relationship between dietary fibre (wheat bran), particle size and their overall effect on gut health, 
nutrition and feed cost in broiler production.  
1.1. Hypothesis  
Feeding broilers diets with arabinoxylan-type fibre (wheat bran) and coarse maize particle sizes 
will improve growth performance, gut morphogenesis and immune status in broilers. 
1.2. Objectives  
The main objective of this study was to explore the effect of dietary fibre levels (using wheat bran 
(WB) as a dietary fibre source) and maize particle sizes on broiler growth performance, gut and 
immune health status. 
Specific objectives were to: 
1.  Evaluate the main and interactive effects dietary fibre levels (using wheat bran (WB) as a 
dietary fibre source) and maize particle sizes had on broiler: 
a. Nutrient digestibility  
b. Growth performance 
c. Carcass characteristics 
d. Caecal butyric acid concentration 
e. Caecal short-chain fatty acid profile 
f. Caecal microbial population and pH 
g. Gut morphology  
h. Haematological indices 
i. Serum glucose content 
j. Immune status   
2. Determine the cost effectiveness of such diets and implications for feed manufacturers 
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CHAPTER TWO 
  LITERATURE REVIEW 
2.1. The Ghanaian poultry industry 
About 80% the Ghanaian poultry industry is primarily made up of medium (120, 000 birds – 50, 
000 birds) and small scale (below 10, 000 birds) businesses with 20% being made up of privately 
owned large scale (over 50, 000 birds) commercial poultry farms (Anon, 2019). Normally, 
chickens (Gallus gallus domesticus) are reared for their meat, feathers, eggs and aesthetic value 
(USDA, 2017). In Ghana, chicken is the most consumed poultry meat followed by that of guinea 
fowls, ducks, turkeys and ostrich (USDA, 2017). Indigenous chicken production, serves as an 
emergency source of funds and food for most people living in the rural areas (Kryger et al., 2010). 
Patterns observed in the growing population and the emergence of new hotels, rest stops, eating 
joints and restaurants has led to a rise in the demand for chicken. (5m editor, 2011). However, the 
domestic production of chicken is declining due to the high demand for imported frozen chicken 
(Woolverton and Frimpong 2013). Reduced prices and pre-cut nature of imported frozen chicken 
makes them the preferred choice of local consumers. Annually, Ghana spends about GHȼ 2,150 
million in the importation of chicken and this supplies about 50% of the local demand 
(Appiakorang Jnr, 2019; Arhinful, 2020).  
In addition to the preference for imported frozen chicken, broiler production in Ghana is affected 
by a lot of consistent setbacks. High prices of feed ingredients have been a persistent factor 
affecting feed cost in broiler production in Ghana (Alabi et al., 2017). This is primarily because 
feed accounts for 60-70% of overall production (USDA, 2017). Globally, maize, soybean, millet 
and wheat are the conventional feed ingredients used in the preparation of broiler diets (Lindberg, 
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2014). These raw materials are also in high demand for human consumption resulting in a 
continuous competition between animals and humans for these cereals and grains (Donkoh et al., 
2003). In Ghana, maize, wheat bran and soybean meal form about 60, 6, and 20 percent 
respectively of broiler diets (Andam et al., 2017). Due to this, 30% of locally produced maize is 
used in the production of poultry (broiler) feed (FAO, 2014). 
2.2. The Impact of Feed Formulation on Broiler Growth and Feed Cost 
Feed ingredients used in broiler diets are variable based on factors such as breed, age, sex, purpose 
and strain of birds. Globally, maize, wheat, sorghum and millet serve as energy sources in broiler 
diets (Onu and Aniebo, 2011). In Ghana, locally available protein-based ingredients used in broiler 
diets include: fish meal, cotton-seed meal, kernel cake, copra cake, groundnut cake meal and 
soybean cake (USDA, 2017). Dietary manipulation of these feed ingredients must be geared 
towards making animal production more efficient and profitable (Makkar, 2016). Currently, 
various management and feeding strategies are being adapted by nutritionists to make this possible. 
Feeding strategies such as: the inclusion of treated unconventional feed resources in diets for 
monogastrics, phase feeding and the formulation of feed according to the breeders’ specifications 
have been employed (Makkarl., 2016). These feeding strategies aim at promoting optimum 
nutrient utilization to enhance animal performance. However, the ability of monogastrics to utilize 
feed is largely dependent on factors such as: (1) how well diets are formulated and (2) the 
nutritional composition of their feed (Adeola et al., 2016).  
The inclusion of dietary fibre (DF) is limited in broiler diets due to its negative effect on 
bioavailability of nutrients (Walugembe et al., 2015). Generally, all broiler diets contain an amount 
of dietary fibre due to the grains and legume-based feed ingredients used in the manufacture of 
broiler feed. According to Mateos et al. (2012), feed manufacturing companies include up to 3% 
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crude fibre in broiler diets. This is due to the absence of endogenous enzymes suitable for the 
digestion and utilization of fibre.  
2.3. Dietary Fibre 
Indigestible carbohydrates can be referred to as dietary fibre (Mudgil and Barask., 2013). Dietary 
fibre is basically the non-starch polysaccharides (NSPs) and lignin components present in plant 
cell walls (Lindberg, 2014). However, resistant starch and oligosaccharides are also termed as 
dietary fibre because of their similar physiological characteristics as lignin and NSPs (Perry and 
Ying, 2016) (Figure 2.1). Dietary fibre was originally referred to as roughage, bulk, or ballast 
before 1965 and measured as ‘crude fibre’ (Chawla and Patil, 2010). Scientists such as McCance 
and Lawrence later modified this definition to describe roughage as the indigestible part of plant-
based foods obtained after a process of solvent, dilute acid and dilute alkali extraction is carried 
out (Dai and Chau, 2017). 
 
 
 
 
 
 
 
 
Figure 2. 1: Components of carbohydrates (Dai and Chau, 2017) 
 
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However, the term ‘dietary fibre’ was introduced by a British physician, Eben Hipsley in 1953 
where he defined it as the non-digestible constituents of the plant cell wall which is unavailable 
for digestion (Hipsley, 1953; Chawla and Patil, 2010; Phillips and Cui, 2011). The Codex 
Alimentarius Commission on Nutrition and Foods for Special Dietary Uses (CCNFSDU) accepted 
an official definition of DF in 2009 (Codex Alimentarius, 2009). Dietary fibre was officially 
defined as “carbohydrate polymers with 10 or more monomeric units, which are not hydrolyzed 
by endogenous enzymes in the small intestine of humans, and which are either edible carbohydrate 
polymers naturally occurring in the food, or carbohydrate polymers which have been obtained 
from raw food materials by physical, enzymatic or chemical means or synthetic carbohydrate 
polymers.” The commission on the other hand, indicated that based on scientific evidence, 
qualified national authorities may approve descriptions ‘b’ and ‘c’ (Codex Alimentarius 
Commission, 2009). However, points ‘b’ and ‘c’ are subject to approval from the qualified national 
authorities based on scientific evidence that proves the physiological effect of dietary fibre on 
health. (Codex Alimentarius Commission, 2009).  
2.3.1. Types of dietary fibre  
The components of DF can be grouped under total non- starch polysaccharides (TNSPs), 
oligosaccharides, analogous carbohydrates (such as resistant starch), associated NSPs substances 
and lignin (Dhingra et al., 2012) (Figure 2.2). 
2.3.1a. Oligosaccharides 
These are digestion-resistant carbohydrate polymers with 3-9 monosaccharide units (Capuano, 
2017). Examples of oligosaccharides include fructo-oligosaccharides (FOS), inulin, polydextrose, 
xylosaccharides and resistant maltodextrins and galacto-oligosaccharides (Hamaker and Tunchul, 
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2014; McCleary, 2014). They are absent in the plant cell walls hence were not initially classified 
as dietary fibre until 2009. Fructo-oligosaccharides (FOS) and inulin are collectively known as 
fructans (Mensink et al., 2015). They are usually found in fruits and vegetables such as bananas, 
onions, garlic, wheat, asparagus and artichokes (Links, 2018).   
Dietary fibre
Non-starch Oligosaccharides Lignins Substances Analogous 
polysaccharides associated with carbohydrates
NSP and lignin 
complex 
Polyfructoses (Inulin, 
Oligofructans), 
galactooliogosugars
Non-cellulosic Resistant starch, 
polysaccharides synthesized Waxes, 
carbohydrates, 
saponins, 
indigestible 
tannins, cutin, 
dextrins
suberin, 
Cellulose phytates
Figure 2. 2: Components of dietary fibre (Dhingra et al., 2021) 
 
Another common oligosaccharide is galacto-oligosaccharides (GOS). They are made up of 
polymers of galactose and a terminal glucose with 2-10 degrees of polymerization (Holscher, 
2017). Some natural sources of GOS include leguminous seeds and plants such as soybeans, peas, 
cowpea, lentils and lupines (Kao et al., 2016). They can also be produced from lactose (Rodriguez-
Colinas et al., 2012). 
2.3.1b. Analogous carbohydrates - Resistant starch (RS) 
Total plant starch is classified by its digestive rates into: quickly digestible, slowly digestible and 
resistant starch (Dai and Chau, 2017). Resistant starch describes the indigestible part of starch, 
which remains undigested 120 minutes after ingestion (Fuentes‐Zaragoza et al., 2011) as 
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illustrated in Figure 4. Resistant starch is made up of amylose and amylopectin granules which 
form linear molecules bonded by α‐1, 4‐D‐glucan linkages (Haralampu, 2000). Whole grains, 
seeds and barley are sources of RS. 
2.3.1c. Lignin 
It is a complex and multiple-branched polymer formed through dehydrogenative polymerization 
of phenylpropane units into p-hydroxyphenyl, guaiacyl and syringyl polymers (Wang et al., 2019). 
Lignin is not a polysaccharide but it is considered a component of dietary fibre due to its constant 
association with cell wall polysaccharides such as cellulose and hemicellulose (Zhao et al., 2020). 
During plant growth, lignin binds directly or indirectly to cellulose or hemicellulose through sugar 
residues and ferulic acid (Davin et al., 2008). Lignin serves as a protective barrier for plant cell 
walls due to its rigidity (Rinaldi, 2017).  
2.3.1d. Non-Starch Polysaccharides (NSP) 
Non-starch polysaccharides (NSP) are complex non-digestible carbohydrates that make up about 
90% of primary and secondary plant cell walls and are bonded together by α or β-glycosidic 
linkages (Knudsen, 2014). Due to this, they function as structural polysaccharides and normally 
occur together with other compounds such as proteins (Albersheim et al., 2011). Cellulose, pectins 
and hemicellulose are examples of NSPs, which occur in large amounts in plant cell walls. Others 
such as fructans, glucomannans and galactomannans are known as plant storage polysaccharides 
and occur in smaller quantities (Navarro et al., 2019). Most cereals such as wheat, maize and 
sorghum contain NSPs. Figure 2.3 shows NSPs classification. 
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Figure 2. 3: Classification of non–starch polysaccharides (Choct, 2015) 
2.3.1d.1. Cellulose 
Cellulose is the most abundant NSPs found in plants cell walls with small quantities in every plant 
tissue such as the endosperm and cotyledon (Knudsen, 2014). It is made up of linear chains linked 
together by β-1–4 bonds. Usually, cellulose molecules are arranged in a defined manner within 
microfibrils (Lavanya et al., 2011; Moon et al., 2011).  
 
2.3.1d.2. Non-cellulosic NSPs 
Non-cellulosic NSPs are a group of structural polymers with pyranoside sugars held together by 
1-4 linkages (Sinha et al., 2011). These NSPs differ from one other based on the degree of 
branching and their uronic acid content (Căpriţă, et al., 2010). Examples include mannans, mixed-
linked β-glucans, xyloglucan and arabinoxylans (Moreira and Filho, 2008). Table 2.1 shows some 
examples of non-cellulosic NSPs and their properties. 
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2.3.1d.3. Pectins 
Pectins have an α-1-4 glycosidic backbone chain linked to D-galacturonic acid units (Wefers et 
al., 2014). Their gel–like nature gives them the ability to act as intercellular cement and are the 
second most abundant polysaccharides found in fruits and vegetables (Zaragoza et al., 2010). 
Pectins can be grouped into arabinogalactans (legumes and rapeseeds), arabinans (cereal products) 
and galactans (citrus) based on structure and, or degree of substitution (Wefers et al., 2014).  
 
Table 2. 1: Examples of non-cellulosic NSPs, their properties and food sources 
Polysaccharide Monomeric Description Food 
Residue Sources 
Arabinoxylans β-D-xylopyranosyl a. β-(1 → 4)-linked xylose units replaced Wheat, rye, 
α-L- at the O-2 or O-3 position with barley, oat, 
arabinofuranosyl arabinose  rice, 
b. They differ based on the ratio of sorghum 
arabinose: xylose  
c. Ratio of arabinose-xylose influences 
their viscosity 
Mixed-linked β- Glucose a. β-(1 → 3) and β-(1 → 4) linkages Oat and 
glucans present  barley 
b. They are a characteristic of the order 
of Poales such as grasses 
c. Interact with cellulose microfibrils at 
the subaleurone and endospermic cell 
wall  
Galactomannans Galactose, a. Serve as storage polysaccharides in Locust 
Mannans the endosperm of leguminous seeds bean, 
b. Ratio of galactose: mannan influences arabic, tara 
their viscosity and solubility and guar 
c. Viscous nature of some gum  
galactomannans promotes slower 
gastric emptying hence increasing 
satiety 
d. Retains water in seeds hence 
promoting effective seed germination 
e. Replacement for fat in may food 
products since it is noted for the 
unique fat-rich mouth feel 
 
 
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2.3.2. Classification of Dietary fibre 
Each dietary fibre type has its own distinctive physical, chemical, structural and physiochemical 
properties (Daou and Zhang, 2014). Hence, their inclusion in the diets of animals causes different 
physiological effects in the body. Some ways by which dietary fibre is classified include: 
1. Origin or source: plants, native or synthetic sources 
2. Site of digestion: stomach, colon and small intestines. 
3. Products of fermentation: acetic, propionic, valeric, fumaric, lactic acids 
4. Applications: food, pharmaceutical industries (Stephen et al., 2017) 
The physiochemical properties of fibre results in beneficial physiological effects. Ways by which 
dietary fibre can be classified based on their physiochemical properties are as follows:  
5. Structure: linear or nonlinear molecular polysaccharides  
6. Solubility in a buffer at a defined pH: water or alkaline/acids 
7. Viscosity in water or in the digestive system 
8. Fermentability pattern: rate of fermentation and short-chain fatty acids’ profile 
9. Bulking effect (Chawla and Patil, 2010) 
 
2.3.2a. Classification based on solubility and viscosity of dietary fibre 
Solubility of dietary fibre refers to its ability to dissolve in water, a buffer or an enzyme solution 
prepared to suit the aqueous enzyme environment of the digestive system (Elleuch et al., 2011; 
El Khoury et al., 2012). The solubility of dietary fibre depends on factors such as chemical 
(random or orderly arrangement) configuration, physical structures and interactions with other 
dietary fibre types (such as lignocellulosic complex), the presence of a substitution group 
(COOH or SO2), temperature and ionic strength (Choct, 2015). Dietary fibre types with orderly 
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arranged molecules plus less branching is more stable in the solid form than in a solution 
(Guillon and Champ, 2000). Highly branched dietary fibres (gum acacia) and ionic groups have a 
high solubility level (Dhingra et al., 2012).  
The viscosity of fibre refers to its resistance to flow (Guillon and Champ, 2000). It is determined 
by the ratio of shear stress (C): shear rate (c), where an increased shear rate results in an 
increase/decrease solubility (Elleuch et al., 2011). The type and concentration of water-soluble 
fibre influences viscosity (Theuwissen and Mensink, 2008). 
2.3.2a.1. Soluble Dietary fibres (SDF) 
Soluble DFs include pectins, galactomannans gums, mucilages, oligosaccharides (including 
fructooligosaccharides; FOS), β- glucans (oat and barley grains), alginate, and psyllium (Maziarz, 
2013). Also, they are gummy in water and are known to ferment well in an aqueous enzyme 
solution (Esposito et al., 2005). Some water-soluble DFs are viscous in nature while some are not 
(Choct, 2015). Water-soluble dietary fibres with low-molecular weights are highly soluble in water 
and have low viscosity (Dhingra et al., 2012). Such dietary fibres also have short polymer chains, 
which are highly branched at irregular intervals. Water-soluble dietary fibres play a major role in 
maintaining the stability of serum lipid concentration (Surampudi et al., 2016). High viscous 
water-soluble dietary fibres easily dissolves in water but have a slower rate of movement (Dikeman 
and Fahey, 2006). They form gels when in water which thickens the digesta content making 
movement very slow in the gastro-intestinal tract. This results in a delay in gastric emptying 
increasing total transit time in the gastro-intestinal tract. Low nutrient digestion and absorption is 
associated with viscous soluble dietary fibres (Brennan, 2005). Arabinoxylans and mixed linked 
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beta-glucans such as starchy endosperm and aleurone layer of wheat, rye and barley are examples 
of viscous water-soluble dietary fibres (Stephen et al., 2017). 
 
2.3.2a.2. Insoluble fibres (IDF)  
Insoluble fibres refer to indigestible carbohydrates which do not dissolve in water or an aqueous 
enzymatic solution due to the hydrogen bonds that exist between them (Dai and Chau, 2017). 
Figure 2.4 shows the different ways by which IDF can be classified (Papanikou, 2016). Cellulose, 
some hemicelluloses, resistant starch and lignin are examples of insoluble dietary fibre (Williams 
et al., 2017). They have a high water absorbing quality, which promotes a good bulking effect. 
The addition of wheat bran, whole grains and vegetables to a diet increases the rate of passage in 
the gastro-intestinal tract (Kheravii et al., 2018). This goes a long way to maintain the normal 
motility of the gastro-intestinal tract (Ho et al., 2012). 
 
2.3.2b. Classification based on Fermentability  
Fibre fermentability refers to the ability of the beneficial gut microbiota to break down fibre into 
essential products in the gut (Leech, 2017). Examples include beta-glucans, oligofructose, inulin, 
guar gums and pectins. Fermentable fibres promote growth of beneficial microbiota through the 
production of short-chain fatty acids. (Parnell and Reimar, 2012). Some insoluble fibres are 
fermented to some extent as shown in figure 2.4. This is possible based on how porous and 
available the surface area of these insoluble fibres are at a moment. The porosity and availability 
of dietary fibre depends on the chemical structure and source of fibre (Capuano, 2017). The 
hydrogen bonds between the polymers of insoluble fibres (hemicellulose, cellulose and lignin) 
make it increasingly difficult for the microbial degradation (Williams et al., 2017). 
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2.3.3. The Role of Dietary Fibre in Monogastric Nutrition 
Low voluntary intake, reduced nutrient digestibility and utilization as well as overall poor growth 
performance have been associated with the inclusion of DF sources in monogastric diets (Nortey 
et al., 2015). However, most feed ingredients such as cereals and legumes contain a very 
significant amount of dietary fibre (Table 2.2). In addition, poultry often peck at their litter 
materials (example wood shavings) which contain some amount of fibre (Choct, 2015). Recent 
studies have highlighted the positive effects dietary fibre has on monogastrics and nutritive ways 
by which the undesirable effects of dietary fibre can be mitigated (González-Alvarado et al., 
2010; Lindberg, 2014; Choct, 2015; Kheravii et al., 2018). 
 
Figure 2. 4: Classification of dietary fibre based on fermentability (Papanikou, 2016) 
 
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Dietary fibre is known to enhance intestinal mucosa integrity, gut morphology, physiochemical 
properties of digesta and overall gut health (Canibe and Bach Knudsen, 2002; Molist et al., 2012; 
Liu et al., 2012).  
Also, dietary fibre reduces the expression of some immune indicators which may be attributed to 
the presence of stressors and inflammation in the gut (Teng and Kim, 2018; Tiwari et al., 2018). 
As such, inclusion of moderate levels of dietary fibre in monogastric diets is highly 
recommended in recent times. Strategies such as particle size manipulation and supplementation 
of exogenous enzymes have been used in many studies to reduce the negative effects associated 
with DF intake in monogastrics (Anadón et al., 2019). The effect of DF on the physiology of 
monogastrics depends largely on the physical, chemical and physico-chemical properties of the 
fibre used, the level of inclusion in the diet among other reasons (Holscher, 2017). 
Table 2. 2: Proximate nutrient composition of some common cereal grains and co-products 
(g/kg DM) 
 Wheat1 Corn1 Sorghum1 Wheat bran2 Barley2,3,4 DDGS1 
Starch 618 620 690 222 587 86 
Cellulose 13 17 15 72 39 58 
NCP       
Soluble 19 25 4 29 56 34 
Insoluble 62 38 47 273 88 158 
NSP       
Arabinoxylan 81 17 17 238 12 61 
β-glucan 8 6 1 24 43 63 
Mannose 2 2 1 5 2 9 
Galactose 3 8 3 9 2 14 
Uronic acids 4 8 4 15 2 16 
Total NSP 95 81 66 374 167 192 
Lignin 18 8 16 75 35 32 
Dietary Fibre 112 89 83 449 202 322 
DM = dry matter, NCP = non-cellulosic polysaccharides; NSP = non-starch polysaccharides; 
DDGS = distilers dried grains with solubles; 1Jaworski et al. (2015); 2Knudsen (1997); 3According 
Holtekjølen et al. (2006); 4According to Jha et al. (2011) 
 
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2.3.3a. Effect of Dietary Fibre on Voluntary Feed Intake  
The level, nature and type of dietary fibre included in monogastric diets affect voluntary feed 
intake of monogastrics (Ratanpaul et al., 2019). Early gut fill and satiety could be reasons for low 
voluntary feed intake (Ndou et al., 2013). Viscous and soluble fibres may lead to low voluntary 
feed intake by increasing the period of chewing and saliva production (Howarth et al., 2001). In 
order to break down bulky fibres, monogastrics will have to chew ingested feed for a relatively 
longer period of time. The prolonged stay of the ingested feed in the mouth increases the amount 
of saliva produced.  This can result in early satiety which may affect the level of energy intake. 
When feed formulated has low energy values, an early satiety will cause a decrease in energy 
intake below the required level (Burton-Freeman, 2000). However, a well-balanced diet with a 
fibrous component may be beneficial to layers in promoting general performance and production 
(Gurbuz et al, 2011; Martínez  et al., 2015). In a study conducted in barrows using sugar beet pulp, 
a lower voluntary feed intake was recorded when the inclusion of sugar beet pulp was higher than 
35.0% (Zhang et al., 2013). Also, the movement of bulky and viscous fibres along the walls of the 
stomach may cause an increase in the secretion of gastric juices (Benelam, 2009). This may lead 
to a distension of the stomach causing a feeling of satiety through afferent vagal signals sent to the 
nervous system (Burton-Freeman, 2000). 
2.3.3b. Effect of Dietary Fibre on Nutrient Digestibility 
Even though dietary fibre is not digested by endogenous enzymes, their presence in broiler diets 
can negatively or positively influence digestion and nutrient utilization (Tiwari et al., 2018). 
However, this is subject to factors such as age, breed, level of inclusion, type and nature of fibre 
(Jha and Berrocoso, 2015).  
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The type and nature of dietary fibre may affect digesta viscosity, transit time and faecal bulk 
(Zhang et al., 2013). For instance, soluble dietary fibre has a high-water holding capacity which 
delays gastric emptying and reduces nutrient absorption (Serena et al., 2008). On the other hand, 
insoluble fibre may bind to organic compounds, increase gut transit time resulting in a higher 
portion of digesta moving to the hindgut (Montagne et al., 2003). Dietary fibre can also form 
complexes with organic compounds, thus preventing their digestion and absorption. Also, the 
movement of some types of dietary fibre such as rice hulls may cause an abrasive effect on the 
intestinal wall leading to losses of endogenous cells and lumen nutrients (Mateos et al., 2012). 
This may reduce the rate of absorption as the number of endogenous cells and pores which make 
up the villi is reduced. With respect to age, nutrient digestibility in mature animals may be higher 
than that in young animals (Lindeberg, 2014). This may be due to the fact that, the gastro-intestinal 
tract (GIT) of matured animals may be well adapted to the fibrous nature of the feed (Le Goff et 
al., 2002). As such, the rate of digestion and fermentation (in the hindgut) will be higher in the 
mature animals compared to the younger animals. According to Jha et al. (2019), the level of fibre 
inclusion in a diet is inversely related to the level of digestion and nutrient utilization. 
However, recent studies have indicated that, the presence of structural components such as 
dietary fibre can enhance nutrient digestibility in broilers (Kimiaeitalab et al., 2017). This can be 
attributed to their positive effects on development of digestive organs such as the gizzard, crop 
and proventriculus (Jiménez-Moreno et al., 2013). This results in an increase in enzymatic 
activities (secretion of cholecystokinin and pepsin), secretion of HCL and reverse contractions 
which are key indicators of enhanced nutrient digestibility (Svihus, 2014). Also, gut motility is 
improved which encourages better mixing of digesta with digestive juices (González-Alvarado et 
al., 2007). In a study carried out by Jiménez-Moreno et al. (2013), coarse fibrous diets fed to 
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broilers positively affected the secretion and efficacy of digestive enzymes. This was attributed 
to a longer retention time in the gizzard, which led to an effective breakdown of the structural 
components. Bacterial fermentation in the crop was enhanced as well as protein digestibility 
(Afsharmanesh and Pourreza, 2005; Classen et al., 2016).  
Knowledge about the suitable inclusion rate, type of fibre, age and other dietary components 
gives the nutritionist the opportunity to formulate diets that can mitigate the negative effects of 
dietary fibre and enhance their beneficial effects on nutrient digestibility in broilers. 
2.3.4. The Gut Microbiota and Dietary Fibre Fermentability in Poultry 
The microbiota plays various roles in the gastro-intestinal tract and are often referred to as the 
‘forgotten organ’ (O'Hara and Shanahan, 2006). The microbiota of the gut refers to commensal 
and pathogenic bacteria (Montagne et al., 2003). An optimum intestinal microbiota has a higher 
ratio of commensal bacteria to pathogenic bacteria or at most a balance (Thursby and Juge, 2017). 
Commensal bacteria include species belonging to: Lactobacillus, Streptococcus, Bifidobacteria, 
Bacillus and Saccharomyces (Kabir, 2009). They have the ability to act and protect their host by 
preventing the colonization and invasion of pathogenic bacteria (Listeria spp., Salmonella spp., C. 
perfringens and Campylobacter jejuni) (Mor-Mur and Yuste, 2010; Khan et al., 2019). Pathogenic 
bacteria are infectious microorganisms, which cause diseases (Montagne et al., 2003). Gut 
microbes secretes enzymes, which acts on the fibre substrates. Cellulolytic bacteria secrete 
cellulase to act on cellulose (Karmakar and Ray, 2011) while amylolytic bacteria secrete amylase 
to act on starch (Gopinath et al., 2017).  
Fibre fermentability refers to the ability of the beneficial microbes to break down indigestible fibre 
sources to produce short chain fatty acids and other metabolites (Jha and Berrocoso, 2015). In the 
absence of fibre-degrading endogenous enzymes, dietary fibre is degraded and fermented by the 
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gut microbial population. Even though fibre fermentation may occur along the gut, it largely occurs 
in the caeca where there is a dense population of microbes (Kheravii et al., 2018). The principles 
of bacterial fermentation have been widely studied than those of other microbes. Studies suggest 
two different groups of bacteria exist in the gut based on their mode of operation: free-living 
bacteria and substrate-dependent bacteria (Vermeulen et al., 2018). During fermentation, 
substrate-dependent bacteria form a colony around fibrous particles by adhering to their surfaces 
in order to ferment them (Hamaker and Tuncil, 2014). Strains of bacteria such as Lactobacillus 
spp., Enterococcus spp. and Streptococcus spp. have been identified in the upper gut of broilers 
with Lactobacillus spp. forming about 80-90% of the microbial population (Rinttilä and 
Apajalahti, 2013). The dominance of Lactobacillus spp. may be due to their ability to exist in a 
highly acidic environment such as the crop. Gong et al. (2008) reported Lactobacillus aviaries and 
Lactobacillus salivarius as the dominant bacteria species found in the upper gut of broilers. In the 
caeca of chickens, bacteria from the orders, Clostridiales, Bacteroidales and Lactobacillales, have 
being identified (Torok et al, 2011). Furthermore, it was observed that these bacteria disappeared 
after sometime due to reasons such as: (1) high rate of bacterial washout, (2) high pH and (3) rapid 
flow of digesta (Torok et al, 2011).  
Fermentation of arabinoxylans, pectin and soluble β-glucans usually occurs in the proximal colon 
and caecum with that of cellulose occurring at the distal part of the colon (Quinn, 2017). This may 
be an indication that dietary fibre fermentation is site-specific which could be due to the presence 
of particular strains of bacteria. Bacterial fermentation in the lower gut in very efficient as 
undigested feed residues from the upper gut are used as substrates (Williams et al., 2017). Hence, 
there is relatively little competition between the host and lower gut microbes for the same feed 
resources. As such, feeding monogastrics with fibrous diets will rather provide suitable substrates 
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for the metabolic activities of lower gut microbiota while providing the host animal with end 
products of fermentation such as SCFAs (Den Besten et al., 2013). In the absence of complex 
indigestible polysaccharides, the lower gut bacteria ferment indigestible protein sources in order 
to obtain energy. This leads to the production of toxins and carcinogens (protein fermentation) and 
phenols, indoles and ammonia (amino acid fermentation). The presence of these can be harmful to 
the health of the monogastric animal. Hence, addition of dietary fibre to monogastric diet is 
essential to maintain efficient metabolic processes and gut health. 
2.3.4a. End products of Dietary Fibre Fermentation 
End products of bacteria fermentation vary based on the source and physiochemical properties of 
the dietary fibre (Jha and Berrocoso, 2016). However, short chain fatty acids (SCFAs) or volatile 
fatty acids (VFAs), gases such as hydrogen (H2), carbon dioxide (CO2) and methane (CH4) are 
generally produced as end-products of fibre fermentation (Jha and Berrocoso, 2015). Figure 2.5 
shows the process of dietary fibre fermentation and the end products produced. The most common 
SCFAs produced are: acetate, succinate, propionate, butyrate and lactate. Acetate contributes about 
60% of the total SCFAs produced with butyrate and propionate making about 15 and 25% (Jha et 
al., 2019). Growing pigs and gestating sows derive 15% and 30% of their energy requirements 
from SCFAs (Bedford and Gong, 2018). 
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Figure 2. 5: Dietary fibre fermentation end products (Lindberg, 2014) 
 
2.3.5. Dietary Fibre as a Potential Prebiotic in Poultry Nutrition 
The incidence of enteric diseases is of a great worry to farmers due to their associated high 
mortality rate, low productivity and contaminated poultry products (Hajati and Rezaei, 2010; 
Ayeh-Kumi et al., 2016). Research findings over the years have conclusively pointed to the crucial 
role gut microbiome play in promoting growth and maintaining optimal health in poultry 
(Montagne et al., 2003; Jha et al., 2019; Yegani and Korver, 2008; Yadav and Jha, 2019). 
Composition of broiler diets has been established as a primary source by which gut microbiome 
can be modulated (Yadav and Jha, 2019). Consequently, the inclusion of prebiotics in poultry diets 
is increasingly becoming popular due to their beneficial effect on gut microbiome (Ricke et al., 
2020). Recent findings have proven their role as growth and gut health promoters making 
prebiotics a potential substitute for antibiotic use in poultry nutrition (Solis-Cruz et al., 2019).  
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Gibson and Roberfroid originally defined prebiotic as a “non-digestible feed ingredient that 
beneficially affects the host by selectively stimulating the growth and or activity of some beneficial 
bacteria in the colon, and thus improves host health” (Gibson et al., 1995; Ganguly, 2015). 
However, in 2010, Gibson and his colleagues redefined prebiotics as “a selectively fermented 
ingredient that allows specific changes, both in the composition and or activity of the 
gastrointestinal microbiota that confers benefits” (Gibson et al., 2010). Prebiotics must be 
fermentable by intestinal microbiota, resistant to gastrointestinal absorption, gastric acidity and 
hydrolysis by endogenous enzymes (Gibson et al., 2004). One critical characteristic of a prebiotic 
is its ability to enhance the selective growth and metabolism of indigenous intestinal microbiota. 
Prebiotics do not introduce novel forms of bacteria but rather serve as a substrate for the already 
existing ones. The inclusion of non-digestible carbohydrates in poultry diets have reportedly 
enriched the counts and diversity of gut microbiome such as Lactobacilli and Bifidobacteria 
(Gibson and Roberfroid, 1995; Singh et al., 2017). Currently, the possible effects of prebiotics on 
other beneficial microbes such as butyrate-producing microbes have been reported even though 
the exact mode of action is yet to be fully understood (Thomas et al., 2015). 
Most prebiotics are plant-based (Slawinska et al., 2019). They are primarily dietary fibres; 
predominantly oligosaccharides of galactose, fructose or mannose but favourable effects of certain 
proteins, lipids and peptides on gut microbiome (Hajati and Rezaei, 2010) have been reported. 
Examples of specific prebiotics include: stachyose, fructooligosaccharide (FOS), 
transgalactooligosaccharide (TOS), inulin, RS, glucooligosaccharide, xylooligosaccharide, 
isomaltooligosaccharide, lactulose, soybean oligosaccharide, polydextrose, lactosucrose and NSPs 
such as β-glucans (Propulla, 2008; Pourabedin and Zhao, 2015; Hutkins, et al., 2016; Ricke, 2018). 
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Natural plant sources such as tomato, garlic, leek, chicory and honey also exert prebiotic effects 
(Ganguly, 2013).  
Basically, dietary fibre as a prebiotic is indigestible by gut endogenous enzymes as only about 20 
endogenous enzymes glucosidases have been discovered to digest some starch polysaccharides 
(Holscher, 2017). Hence most dietary fibre remains undigested till it reaches the caeca where it 
undergoes possible microbial fermentation (Józefiak et al., 2004). Gut bacteria (predominantly 
Bacteriodes) through the symbiotic relationship that exist between the microbiota and the host 
mostly carry out microbial fermentation (Holscher, 2017). When dietary fibre is consumed by a 
host, it functions as biological agent, which serves as a substrate for microbial growth and 
metabolism. The host in turn benefits from the fermentative end products such as SCFAs. The gut 
microbes are able to ferment DF due to their genetic nature that allows them to produce 
carbohydrate-active enzyme (CAZymes) such as glycoside hydrolases, glycosyltransferases, 
polysaccharide lyases, and carbohydrate esterases (Flint et al., 2012). These enzymes are activated 
based on the substrate binding site available on the undigested DF. The substrate-binding site 
available is influenced by the properties of DF such as chemical structure. Physiochemical 
properties such as the extent of fermentability are influenced by how soluble or viscous the fibre 
type is (Elleuch et al., 2011; McRorie and Fahey, 2013). Hemicellulose, cellulose and lignin are 
insoluble, less viscous hence less fermentable as compared to soluble fibre. Due to their less 
viscous nature, gut transit time is quicker therefore lowering the extent of microbial fermentation. 
In their work, Abazari et al. (2016) observed an increase in the counts of Lactobacillus spp. when 
broilers were fed rice husks. On the other hand, oligosaccharides, fructans, resistant starch, pectins 
and β-glucans are highly viscous and very soluble, hence, are easily fermentable. Feeding birds 
infected with E. tenella soy soluble carbohydrates increased the counts of lactic acid bacteria 
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leading to their survival (Lan et al., 2005). In addition, fibre levels in a particular diet significantly 
influences the growth and diversification of the microbial community (Mateos et al., 2012). 
A lot of theories about how dietary fibre work as prebiotics have been reported, even so, these 
mechanisms are not exclusive (Figure 2.7). Generally, the production of SCFAs triggers a series 
of actions such as a low pH, which in turn enhances the rate of digestion and nutrient utilization. 
Specific mode of actions employed by gut microbes include: 
a. Bacteria antagonism: Beneficial bacteria inhibit the growth of pathogenic bacteria through 
competition for limiting nutrients and production of toxins (such as curvacin. nisin, and 
bifidocin) (Ricke, 2003; Solis-Cruz et al., 2019). As a result, the gut microbiota population 
shifts more towards the non-pathogenic bacteria. For instance, Fukuda et al., (2011) 
established a primary relationship was established between the survival of mice infected 
with enterohaemorrhagic E. coli 0157: H7 and the increase in counts of Bifidobacterium 
species (Fukuda et al., 2011). In addition, acid-intolerant pathogens such as Salmonella, E. 
coli, and C. perfringens survive at a pH range of 5.4-7.2. However, the production of 
SCFAs by beneficial microbes can lower the pH to about 5 or even below, which indirectly 
inhibits the growth of pathogenic bacteria. Butyric, acetic and propionic acids directly 
destroy pathogenic bacteria by attacking their cell structures (cell wall and cytoplasmic 
membrane) and inhibiting their cellular functions related to cell synthesis and development 
(Ricke, 2003; Fernández-Rubio et al., 2009).  
b. Stimulation of immune system: The increase in beneficial bacteria, prevention of pathogen 
adherence to intestinal mucosa and increase in immunoglobulin protection are some 
immunological effects linked with oligosaccharides (Seifert and Watzl, 2007). Dietary 
supplementation of fructooligosaccharide-inulin reduced the counts of viable Salmonella 
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enteritidis and decreased inflammasome activation (Babu et al., 2012; Pourabedin and 
Zhao, 2015).  
 
 
 
 
 
 
 
 
 
 
 
 
Figure 2. 6: Mechanisms by which dietary fibre & SCFAs work as a prebiotic (Pourabedin 
 
and Zhao, 2015) 
 
Also, initial stages of Clostridium perfringens infection was contained by feeding broilers 
mannan-oligosaccharides. The mannan-oligosaccharides helped induce a T-helper type-1 
cell-associated control pathway, which is responsible for producing proteins that promote 
the production of antibodies and phagocytosis. According to Buzás et al. (2006), an agonist 
relationship exists between dietary fibre and toll-like receptors which aides in the control 
of pathogens and their activities. 
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c. Improved intestinal morphological structure: Increased villi height, reduced crypt depth 
and villi height to crypt depth ratio (VH: CD) in different parts of broiler gut (Chen, 2003; 
Rehman et al., 2007) have been associated with the presence of DF in broiler diets. The 
increase in villi height and VH: CD improves gut development, which enhances nutrient 
digestion and absorption (Jha et al., 2019). In studies conducted by Loddi (2003) and 
Pelicano et al. (21005), longer villi height was observed when birds were fed MOS. In 
addition, Johansson et al. (2008) indicated a relationship between the dietary 
supplementation of prebiotics and multiplication of intestinal goblets cells; goblet cells are 
needed for the production of mucins. Mucins attach themselves to pathogens while 
preventing their attachment to intestinal mucosa. 
2.3.5a. Effect of Dietary Fibre on the Production of Short Chain Fatty Acids (SCFAs) 
Also, short-chain fatty acids (mostly butyric, acetic, propionic, valeric) are produced along the gut 
through the microbial fermentation of indigestible fractions of a diet (Holscher et al, 2015). Short-
chain fatty acids are organic compounds with a carboxyl functional group having the chemical 
structure, R-COOH (Haq et al., 2017). Unlike pathogenic bacteria, beneficial bacteria are able to 
produce SCFAs (Jamroz et al., 2002). They serve as a source of energy for gut microbiota with 
about 90-99% used or at times absorbed back into the gut (Ruppin et al., 1980). Acetic acid 
positively affects the blood-brain barrier and serves as a source of energy for muscle tissue in the 
liver (Perry et al., 2016). Propionic acid is usually used as a substrate for gluconeogenesis (De 
Vadder et al., 2014). Butyric acid is a preferred source of energy for metabolic activities of 
colonocytes and enterocytes. Again, an increase in butyric acid levels enhances gut mucosal health 
of monogastrics by inhibiting the occurrence of GIT disorders (Bedford and Gong, 2018). Feeding 
coarser particles or supplementation of a butyrate product improved body weight gain and feed 
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conversion ratio (FCR) of broilers significantly (Qaisrani et al., 2015). To add, butyric acid is also 
known to reduce hindgut protein fermentation because it suppresses protein-fermenting 
microbiota, especially the gram-negative population in broilers (Gunal et al., 2006). The reduction 
in the colonization of harmful bacteria in the digestive tract of broilers was attributed to the 
beneficial effect of SCFAs (Zhang et al., 2011 and Chamba et al., 2014). As stated earlier, the 
production of SCFAs lowers gut pH. This creates a concentration gradient enabling the diffusion 
of SCFAs into the cell walls of pathogenic bacteria to inhibit cellular synthesis and development. 
Generally, SCFAs: a) stimulate nutrient digestibility through the enhancement of proteolytic 
activities; b) boost beneficial bacteria growth through their bacteriostatic and bactericidal effects 
on harmful bacteria; c) promote digestive enzymatic processes; d) encourage gut health and e) 
lower intestinal pH (Mansoub et al., 2011; Papatsiros et al., 2013).  
Dietary composition is a major determinant of the efficiency and quantity of SCFAs produced in 
the gut (Papatsiros et al., 2013). Dietary fibre is a key component that largely influences the 
production of SCFAs due to their indigestible but fermentable nature. The production of SCFAs 
is one of the intermediate metabolic pathways by which gut microbiota utilizes dietary fibre as an 
energy source in animals (Hsieh et al., 2015). Due to their heterogeneous nature, they serve as a 
means by which a broad spectrum of SCFAs is produced. The varied dietary fibre compositions in 
plant-based diets was reported to have influenced the production of SCFAs in broilers (Tsukahara 
and Ushida, 2000). Additionally, the type of dietary fibre determines the composition of SCFAs 
produced (Gibson et al., 2010). Inclusion of dried distillers’ grains with solubles and wheat bran 
in broiler diets resulted in an increase in production of acetic, butyric and propionic acids in a 
decreasing order (Walugembe et al., 2015). Furthermore, fructans are noted for their direct effect 
on the production of acetate and indirect production of butyrate through microbial cross-feeding 
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(Holscher et al., 2015). Fermentable dietary fibres such as arabinoxylan-oligosaccharides, galacto-
oligosaccharides and inulin-type fructans largely influence the production of SCFAs. This may be 
due to the effect of increasing the counts of saccharolytic bacterial population (Gibson et al., 2010).   
Again, the level of DF included in a diet can influence the profile and concentration of SCFAs 
produced (Prasad and Bondy, 2019). This may be due to the linear increase in the proliferation of 
beneficial bacteria and their fermentative processes as the level of DF increases (Kheravii et al., 
2018). However, in testing for the effect of DF levels on the production of SCFAs, Bogusławska-
Tryk et al. (2015) observed an increase in levels of SCFAs in the caecum and ileum when 
lignocellulose was fed at 0.5% as compared to 0.25 and 1% inclusion rates. Likewise, Walugembe 
et al. (2015) observed a reduction in butyric acid levels in broilers fed diets containing up to 80 
g/kg each of WB and dried distillers’ grains with solubles (DDGS) as compared to those fed 0% 
fibre. The lack of increase in SCFAs despite the increasing levels of DF in the two studies 
mentioned above was attributed to the effect of the fibre type used, insoluble fibre, on gut transit 
time. Insoluble fibre is known to reduce gut transit time, which may have reduced the extent of 
fermentation. Total SCFAs and butyric acid levels were elevated when birds were fed diets with 
3% WB in a study conducted by Shang et al. (2020). The inconsistencies observed from these 
reports can also be attributed to the differences in breed, age or stage of gastro-intestinal 
development of birds (Kheravii et al., 2018). Again, consistency in the daily intake of a fibre type 
may affect SCFAs production (Den Besten et al., 2013). Work done by Heo et al. (2014) showed 
that fermentation of raw potato starch (resistant starch) was possible in pigs when dietary 
treatments were fed consistently for 21 days. This may be due to a progressive change in the 
microbial profile in response to the type of fibre fed over the period of time. Hence, changing an 
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insoluble fibre-based monogastric diet abruptly to a soluble fibre-based diet might decrease the 
amount of SCFAs produced due to a change in microbial profile. 
2.4. Particle Size   
Particle size refers to the fineness or coarseness of an ingredient or feed (Amerah et al., 2007a). It 
is expressed as geometric mean diameter (Nir et al., 1994a). Any variation in particle size 
distribution is known as geometric standard deviation (GSD; Sgw) which helps to establish a range 
of variation and determines uniformity (Amerah et al., 2007a). Addo et al. (2012) reported that a 
smaller geometric standard deviation indicates a high uniformity. Particle size distribution of feed 
or feed ingredient can be determined by dry or wet sieving (Ruhnke et al., 2015; Kalivoda et al., 
2017). Usually, dry sieve analysis is usually carried out on feed samples while wet sieve analysis 
can be performed on feed samples, excreta or digesta (Ruhnke et al., 2015). 
2.4.1. Importance of Dietary Particle Size in Poultry Nutrition 
 
Birds and layers consume diets based on their taste, visual, tactile and olfactory stimuli (Picard et 
al., 2002). According to Gentle (1979), birds use their mechanoreceptors (found on their beaks) to 
differentiate between particle sizes. For instance, chicks are attracted to and prefer larger and 
brightly coloured feed particles (Schiffman, 1968; Oppong-Sekyere et al., 2012). However, their 
preferences tend to change within the course of their growth (Nir et al., 1989) and according to 
Gentle (1979), this may be influenced by the growth in size of a bird’s gape. These characteristics 
of a bird’s physiology makes the knowledge about particle size in poultry diets essential in 
achieving the desired growth performance and productivity. 
In previous years, little attention has been given to the role particle size plays in feed manufacturing 
and its subsequent effect on the optimal growth and productivity of poultry. However, based on 
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the physiological needs of the monogastric animal, the optimal ingredient particle size will 
enhance efficient nutrient utilization and productivity (Nir and Ptichi, 2001). This may be because 
of the influence of particle size on the surface area available for enzymatic action (Addo et al., 
2012). For example, researchers have established a link between larger particles in mash diets and 
higher rate of amylase activity and bile acid concentration (Svihus., 2011). This may be due to the 
longer grinding and transit time, which encourages better digestion. Yegani and Korver (2008) 
reported the need to provide monogastrics diets with uniformly distributed particles in order to 
optimize performance. Betscher et al. (2010) attributed the improved morphological structure, gut 
health and broiler performance to the positive effect of diet structure and a well-distributed feed. 
Again, dietary particle size affects the development of digestive (Zaefarian et al., 2016) organs 
and an optimal performance of the GIT is crucial in a bird’s performance (Mateos et al., 2012). 
According to Nir and Ptichi (2001), dietary particle size of mash diets influences the extent of 
grind by the gizzard, hence directly affects gizzard weights of birds. Excessive milling and thermal 
treatments to produce pelleted or highly processed feed may limit the role particle size plays in 
animal production (Ruhnke et al., 2015). 
2.4.1a. Factors that Influence Dietary Particle Size in Poultry Nutrition 
Feed and ingredient processing are important in broiler nutrition as the final product can improve 
or destroy the digestive physiology and health of the animal (Yegani and Korver, 2008). Generally, 
the desired target size of feed, normally influenced by age of the animal, determines the conditions 
for the grinding processes (Oppong-Sekyere et al., 2012). The age of the animal is considered in 
relation to the stage of their GIT development. Traditionally, grains fed to day-old chicks up to 
three weeks are reduced to fine particles while those for birds above three weeks are ground to a 
coarse texture (Mateos et al., 2012). Also, the type of mill, screen size and speed (of hammers or 
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rollers) influence the particle size of feed (Schofield, 2005; Amerah et al., 2007a). Hammer mills 
produce more regular-sized particles, which are influenced by screen size and hammer speed 
(Koch, 1996). Roller mills, on the other hand, produce a higher proportion of medium to coarse 
particles with a less amount of fines (Nir and Ptichi, 2001). This is influenced by the type of 
corrugation on these rollers. Characteristics of grains such as endosperm hardness, moisture 
content, type of grain, maturity and size determine grinding conditions (Amerah et al., 2007a; 
Kiarie and Mills, 2019). Regular and finer particles are identified with the milling of softer 
endosperms (Carré et al., 2005). A better broiler growth performance is linked to harder 
endosperms when manufacturing mash diets as they give coarser and irregular particles (Pirgozliev 
et al., 2003). Again, cost increases as the extent of grinding increases and this tends to influence 
grinding conditions to a larger extent (Wondra et al., 1995).  
2.4.1b. Effect of Grinding on Feed Utilisation in Poultry Nutrition 
Grinding of some feed ingredients is an inevitable step in the feed manufacturing process (Oppong-
Sekyere et al., 2012). Usually, commercial protein-based ingredients (soybean meal, meat meal 
and canola cake) are pre-processed and are available at an already determined particle size 
(Amerah et al., 2007a). However, the extent of particle size reduction of carbohydrate-based 
ingredients such as cereals and legumes differ per feed mill as they come as raw grains. Hence, 
they have to be ground at individual feed mills to achieve a desired size (Oppong-Sekyere et al., 
2012). Reducing the size of feed ingredients lessens segregation of nutrients during handling and 
makes mixing easier (Pacheco et al., 2018). Particle size reduction is a two-step process that 
involves the splitting of the outer coat to expose the endosperm of a seed (Amerah et al., 2007a; 
Oppong-Sekyere et al., 2012). It is usually done by using hammer or roller mills. According to 
Anguita et al. (2006), grinding conditions are specific to grain sizes, maturity, crystallinity and 
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brittleness. Over the years, feed millers have preferred fine grinding in order to increase surface 
area for the efficient work of digestive enzymes. In pigs, potential negative effects associated with 
fine grinding include development of ulcers in the oesophageal region and increased susceptibility 
to the colonization of harmful bacteria (Nir et al., 1994b). However, the inclusion of structural 
components such as coarse or whole grains in monogastric diets have received much attention 
(Ferket and Gernat, 2006). This is due to the effects on intestinal morphology, microbiota profile 
and better peristalsis movement (Amerah et al., 2007b). The impact of coarse or fine grinding is 
affected by the feed form; mash, crumbled or pelleted diets. The optimum particle size of 
monogastric diets based on maize or sorghum ranges from 600-900μm (Nir et al., 1994a; Amerah 
et al., 2007a). 
2.4.2. Effect of Dietary Particle Size on Growth Performance 
 
There are inconsistencies in the reports of studies carried out on the influence of feed particle size 
on broiler growth performance (Amerah et al., 2007a; Jacobs et al., 2010; Chewning et al., 2012; 
Oppong-Sekyere et al., 2012). The response of broilers to feed particle size is influenced by rearing 
systems, type of grain,  age of bird,  phase at which a particle size is fed, feed form and the stage 
of GIT development (Jacobs et al., 2010; Kheravii et al., 2018). 
Broiler diets must be formulated to improve GIT development right from day one in order to 
achieve an optimal growth performance (Rubio et al., 2020). Previous studies have indicated that 
feeding broilers larger particles stimulates a better development of digestive organs such as crop, 
proventriculus and gizzard (Naderinejad et al., 2016; Kiarie and Mills, 2019). Consequently, this 
enhances an efficient breakdown and absorption of nutrients. Similarly, Nir et al. (1995) reported 
that feeding larger particle sizes to broilers stimulates better development of the gizzard which 
enhances physical and chemical activities; and this can potentially improve nutrient utilization. In 
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addition, optimal nutrient digestion occurs from one to about day 14 in broilers. Hence, strategies 
geared towards improving weight gain potential for a good market weight must be initiated during 
this period (Batal and Parsons, 2002). Rubio et al. (2020) observed no improvement in feed 
conversion ratio when broilers were fed coarser (1,664μm) corn particles during the finisher phase 
(day 28 to day 42). This was attributed to poor development of the GIT during the starter phase 
(day 1 to day 27) such that the birds were unable to effectively utilize the coarser particles during 
the finisher phase. They further indicated that particle size of corn (average of 650μm) fed to the 
birds from day one to 28 may have not been structurally adequate to prepare the GIT for the corn 
particle size fed from day 28 to 42 (1,664μm). On the other hand, Xu et al. (2015a) demonstrated 
a decrease in growth performance when birds were fed coarse particles (1642μm) from day one. 
Feed additives such as premixes are finer, hence can be rejected during feed intake by birds due to 
their selective preference for larger feed particles. Hence, Xu et al. (2015a) attributed the decline 
in growth performance to the consumption of less balanced nutrients. Also, the impact of dietary 
particle size on growth performance can be influenced by the type of rearing system used (Rubio 
et al., 2020). In rearing systems such as deep litter system, structural components such as litter 
(wood shavings) are used as bedding materials in cages. According to Xu et al. (2017), the 
ingestion of wood shavings by broilers reared in a deep-litter system elicits similar effects as the 
consumption of large feed particles; that is mechanical stimulation of the gizzard. On the other 
hand, this is not so in birds reared in a battery cage system due to the absence of a bedding material 
(wood shavings). As such, dietary particle size manipulation must be done considering the 
presence or absence of other structural components in the environs of broilers to avoid negatively 
affecting growth performance. Figure 2.8 shows how particle size of broiler diets triggers a series 
of biological effects. Due to the complex nature of dietary fibre and coarse feed particles, the 
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secretion of digestive enzymes increases in order to break down the complex structure of dietary 
fibre or coarse feed particles. This creates a favourable acidic environment for microbial 
fermentation and seeding of beneficial bacteria. Consequently, nutrient utilization and absorption 
is increased with short chain fatty acids increasing as well.  
2.4.3. Effect of Dietary Particle Size on Microbial Profile  
Primarily, the mode of action by which particle size changes gut microbial profile is primarily 
based on alterations in gizzard activity, gut pH and digesta transit time (Zaefarian et al., 2016). 
 
 
 
 
 
 
 
 
Figure 2. 7: Effect of particle size on nutrient digestion, growth and gut health in poultry 
 (Kheravii et al., 2018) 
As stated earlier, providing broilers coarse feed particles enhances the mechanical activity of the 
gizzard, which triggers the release of digestive enzymes resulting in an acidic environment 
(Engberg et al., 2002). Coupled with the increased digesta transit time, the survival rate of acid-
intolerant pathogenic bacteria (such as E. coli and S. enterica serovar Typhimurium) present in 
feed will be reduced (Svihus, 2014). 
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Also, the acidic environment creates an opportunity for an increase in early seeding of beneficial 
bacteria such as Lactobacilli, Streptococci and Coliform spp. in upper gut (Fuller, 2001). An early 
abundance of non-pathogenic bacteria stimulates the release of compounds such flavonoids (Sulek 
et al., 2014). Flavonoids are critical in maintaining gut integrity and in the stimulation of immune 
responses (Sulek et al., 2014). Inclusion of coarsely ground maize (>1000μm) in broiler diets 
elevated the counts of Lactobacillus spp. and Bifidobacteria spp. but reduced the numbers of 
Campylobacter spp., E. coli and Bacteroides spp. (Jacobs et al., 2010; Singh et al., 2014). 
A fast gut transit time is associated with feeding finer or smaller particles, which reduces nutrient 
digestion and utilization due to the shorter digesta retention time (Amerah et al., 2007b; Kheravii 
et al., 2018). As a result, a greater proportion of digesta accumulates in the distal gut, which can 
be harmful to the host depending on the nature of diet (Kiarie and Mills, 2019). If a soluble diet is 
fed, a lower amount of energy will be made available to the host. This is because the microbes will 
use some of the energy generated for their own metabolic activities (Lan et al., 2005). Hindgut 
protein fermentation leads to the production of toxic compounds such as phenols, amines, 
ammonia and thiols (Timbermont et al., 2011). These compounds create a suitable gut 
environment for the growth of pathogenic bacteria such as Clostridium spp. (Timbermont et al., 
2011).  
2.4.4. Effect of Dietary Particle Size on the Production of SCFAs  
Recent reports indicate a possible effect of dietary particle size on SCFAs production. According 
to Kheravii et al. (2018), the inclusion of large fibrous particles in broiler diets, extends digesta 
passage rate in the foregut while lowering the pH in the crop. This initiates early microbial 
fermentation of DF in the foregut which improves gut health. Bogusławska-Tryk et al. (2015) 
reported early proliferation of Lactobacillus spp. in the crop of broilers when lignocellulose was 
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added to their diets. The early reduction of pH in the crop is essential to the inhibition of pathogenic 
bacteria in the gut (Classen et al., 2016). According to Van Immerseel et al. (2006), SCFAs remain 
longer in un-dissociated forms in a low environmental pH, which enhances their antimicrobial 
properties.  
2.4.4a. Impact of Short-Chain Fatty Acids on Nutrient Utilization and Digestibility 
Nutrient digestion and utilization occur in the gut, hence, a proper functioning gut is essential for 
optimal growth performance of broilers (Jha et al., 2019). The gut is the ultimate hub of a host’s 
immunity; hence if the gut is healthy, available nutrients and metabolites will be geared towards 
growth and development (Montagne et al., 2003). A positive link between the levels of SCFAs in 
the distal gut and broiler growth performance has been established (Singh et al., 2012; Park et al., 
2013). This may due to the positive influence of SCFAs on the development of microscopic 
structures in the small intestines, digestive enzyme secretions, maintenance of intestinal epithelial 
integrity, defense systems and reduction in pathogenic virulence (Guilloteau et al., 2010). Kiarie 
et al. (2014) concluded that the higher levels of acetic and butyric acids in birds fed wheat-based 
diets may have elicited a higher growth performance as compared to birds fed corn-based diets. 
Additionally, via the peptide YY pathway, SCFAs are able to influence nutrient digestion and 
utilization (Park et al., 2013). The peptide YY is a hormone synthesized and secreted in the distal 
ileum and colon in response to the presence of SCFAs in the intestinal lumen. The release of the 
hormone causes ileal brake, where appetite and feed intake are reduced, leading to a delayed gastric 
emptying (Cuche et al., 2000). The extended digesta retention time can promote a better digestion 
and absorption of nutrients in the small intestines (Cuche et al., 2000). The effect of the peptide 
YY hormone on nutrient digestibility and utilization has been demonstrated in rats (Cherbut et al., 
1998) and piglets (Cuche et al., 2000). The ability of SCFAs to regulate intestinal flow goes a long 
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way to promote efficient nutrient digestion and utilization (Pan and Yu, 2014). Inclusion of fibrous 
feed ingredients in broiler diets away from the traditional dietary composition of easily digestible 
components results in the generation of ‘extra’ energy from SCFAs which can improve feed 
conversion ratio (Lan et al., 2005). Due to their acidic nature, the presence of SCFAs in the gut 
increases the rate of protein synthesis by triggering the release of enzymes such as pepsin 
(Muramatsu et al., 1988). 
2.4.4b. Impact of Short-Chain Fatty Acids on Gut Morphology 
Enterocytes and colonocytes are examples of cells that make up the epithelium covering the small 
intestines and colon respectively. Colonocytes are instrumental in the absorption of water, sodium, 
and chloride from undigested feed materials (Hamer et al., 2010). Many factors are identified with 
healthy guts but the morphology of the small intestines structures (villi and crypts) are baseline 
indicators (Wang and Peng, 2008). The villus is noted for its role in digestion and absorption of 
nutrients; hence a longer villus is ideal as it increases the luminal absorptive area of the small 
intestines (Laudadio et al., 2012). On the other hand, the crypt, which serves as the site for growth 
and multiplication of enterocytes, must be shallow (Oliveira et al., 2008). A shallow crypt reflects 
a healthy set of villi, indicating a lower need for the synthesis of new enterocytes for villi growth. 
Therefore, energy can be used for the development of other structures (Miles et al., 2006). Previous 
studies have proven the positive effects of SCFAs, especially butyric acid, on the development of 
gut structure and its functioning (Guerra-Ordaz et al., 2013; Khatibjoo et al., 2018) (Figure 2.8). 
Butyric acid stimulates the occurrence of metabolic activities such as cellular differentiation in the 
epithelium, which may result in an increase in intestinal tissue weight (Fukunaga et al., 2003; 
Rinttilä and Apajalahti, 2013). Kien et al. (2007) observed a linear increase in villi height (VH), 
crypt depth (CD) and villi to crypt depth ratio (VH: CD) of piglets as butyrate levels rose with age. 
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This was attributed to the anti-peristaltic movement of butyrate from the caecum into small 
intestines, which influenced cell proliferation.  
Butyric acid also preserves gut integrity by protecting tight junction proteins to avoid the ‘leaky 
gut’ situation (Sun and O'Riordan, 2013). On the other hand, acetic acid is responsible for effective 
blood flow in the colon and reduces apoptosis (Scheppach, 1994). It also promotes efficient ileal 
motility and mucin production (Liu et al., 2017).  
 
Mucosal 
blood 
flow
Mucus 
Prevention release, 
of colitis SCFAs cellular 
differentiation
Mucosal cell 
proliferation
Figure 2. 8: Effect of SCFAs on gut morphology (Scheppach, 1994) 
 
Some researchers believe that the influence of SCFAs and the microbial community on gut 
structure and function are not exclusive (Liao et al., 2020). This may be due to the spatial 
heterogeneity of microbial communities along the gut (Gong et al., 2007). According to Choi et 
al. (2014), the composition of the microbial communities at every point along the gut may 
pronounce a distinct effect on gut morphology structure. This interaction is significant as farmers 
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can regulate and promote good intestinal development in broilers through dietary manipulation 
(Liao et al., 2020).  
2.5. Wheat bran as a dietary fibre source 
Wheat bran is an insoluble (arabinoxylan and cellulose) DF with about <5% of soluble components 
(β-glucans) (Onipe et al., 2015). It is an agro-industrial by-product obtained after the processing 
of wheat grains (Triticum aestivum L.) into flour (Vermeulen et al., 2018). Based on the variety of 
wheat and the milling process, about 10-19% of WB can be obtained from the kernel while the 
production of wheat offal can yield about 50% WB (Ash, 1992). Annually, about 150 million 
tonnes of WB are gathered as by-products globally (Wanzenböck et al., 2018). Wheat bran is 
highly rich in minerals (iron, zinc and phosphorus), vitamins (thiamin and riboflavin) and bioactive 
components (ferulic acid, flavonoids, and carotenoids) (Andersson et al., 2014; Onipe et al., 2015). 
The chemical composition of WB is shown in Table 2.3. Even though it has a higher oil content 
than the whole grain, it has a lower energy value (Chalamacharla et al., 2018). This necessitates 
the inclusion of oil to WB-based diets to supplement the dietary energy levels. 
2.5a. Influence of Particle Size and Wheat Bran on Butyric Acid Production 
 
In a study conducted by Kjølbæk et al. (2020), the degradation of arabinoxylan-ferulic acid 
linkages in WB resulted in the production of butyric acid as the dominant SCFA in the colon. 
Courtin et al. (2008) and Akhtar et al. (2012) reported positive influences of WB-derived 
arabinoxylans on gut microbial composition, anti-inflammatory effects and intestinal barrier 
function in broilers. 
 
 
 
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Table 2. 3: Chemical composition of wheat bran 
Parameter Composition 
Dry matter (% as fed) 83.6-90.3 
Crude fibre (% DM) 6.3-14.7 
Crude protein (% DM) 14.1-20.5 
Ash (% DM) 4.0-7.3 
Ether extract (% DM) 2.1-5.7 
Neutral detergent fibre (% DM) 32.4-56.5 
Acid-detergent fibre (% DM) 8.4-17.6 
Lignin (% DM) 1.9-5.3 
Starch (Polarimetry) (% DM) 11.1-35.4 
Gross energy (MJ/kg DM) 18.0-19.9 
Heuzé et al. (2015) 
 
  
Additionally, an improvement in growth performance and phosphorus utilization in broilers was 
attributed to the effect of WB phytate (Cavalcanti and Behnke, 2004). On the other hand, the 
phytate effect of WB can be limited when WB-based diets are pelleted. This can be attributed to 
the negative effect of heat treatment on phytate (Cavalcanti and Behnke, 2004). The microbial 
fermentation of WB is very beneficial to the host due to its positive effects on microbial cross-
feeding (Deroover et al., 2017). As mentioned earlier, WB is a very good source of butyrate due 
to its arabinoxylan component (Kjølbæk et al., 2020). However, in the absence of indigenous 
butyrate-producing microorganisms, primary degraders such as Bifidobacteria and Lactobacillus 
spp. feed on WB to produce acetic and lactic acids respectively (De Maesschalck, et al., 2015). 
However, in the presence of Faecalibacterium and Roseburia, acetic and lactic acids can then be 
converted into butyric acid (Moens et al., 2016). Hence, a broad spectrum of SCFAs is produced.  
Vermeulen et al. (2018) identified the effect of WB on cross-feeding and the growth of beneficial 
bacteria in broilers.  
Post-weaning diarrhoea, a common cause of mortalities in newly weaned piglets is caused by E. 
coli and Salmonella five to ten days after weaning (Lu et al., 2018). Molist et al. (2012) fed E. coli 
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K88-challenged piglets with coarsely ground WB. A reduction in the severity of diarrhoea, an 
increase in butyric acid and a decrease in E. coli K88 adhesion were observed. The results obtained 
may be as a result of the reduction effect of butyric acid on the counts of Salmonella and 
Enterobacteria in the gut (Bedford and Gong, 2018). In poultry, the occurrence of Salmonellosis 
causes great economic losses as well as severe infections in humans (Antunes et al., 2016). 
Salmonellosis is caused by Salmonella enterica, serovars Enteritidis or Typhimurium (Dar et al., 
2017). Evidence from studies conducted have proven the antimicrobial role WB plays in the 
reduction of the incidence of Salmonellosis. Salmonella Typhimurium post-challenge and pH were 
reduced when whole wheat was supplemented in broiler diets (Jha et al., 2019). The inclusion of 
arabinoxylo-oligosaccharides (a derivative of partial hydrolysis of WB) in the diets of broilers 
significantly increased the number of Bifidobacteria in the caeca (Eeckhaut et al., 2008). 
According to Belenguer et al. (2006), Bifidobacteria uses arabinoxylans as substrates for the 
production of butyric acid. Due to their lignified and insoluble nature, the inclusion of large or 
moderate particles of WB in monogastric diets is important to promote the growth of beneficial 
bacteria (Zaefarian et al., 2016). Large or moderate particle sizes of WB will increase retention 
time and enhance fermentation (Mateos et al., 2012). 
2.6. Nutritional immune modulation as an alternative to antibiotic usage in broiler 
production  
Nutritional immune modulation refers to the manipulation of the development, maintenance and 
response of the immune system via nutrients and non-nutritive components of feed (Korver, 2012; 
Swaggerty et al., 2019). It is a management tool that exploits how the over or undersupply, balance 
or imbalance of nutrients affects immune response. For instance, the oversupply of selenium in 
broiler diets leads to toxicity, which compromises the immune system (Peng et al., 2011). The use 
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of a single immune measurement as a marker for accessing nutritional effectiveness on immunity 
has been reported to be less effective (Koutsos and Klasing, 2014).  
As a result, recent studies are indicating the need to consider supplementing broiler diets with 
components that enhance the performance of gut microbial community and mucosal immune 
system. Enhancing gut health is a sure way of promoting the overall wellbeing of the immune 
system. The concept of gut health encompasses a diet which provides sufficient nutrients, mucosa 
that maintains gut integrity, and a microbial community that maintains a balanced, healthy 
environment (Montagne et al., 2003). Also, the guts of pigs and poultry contain about 70% of the 
body’s immune cells (Celi et al., 2019), hence the need to promote gut health. An interactive 
relationship between the immune system and the gut microbiota has been reported (Oakley and 
Kogut, 2016). 
Prebiotics such as dietary fibre have been considered in this regard due to their effect on leucocytes 
(Koutsos and Klasing, 2014). For instance, mannanoligosaccharides (MOS) have the ability to 
elevate immune signals in birds (Teng and Kim, 2018). These immune influences may be strongly 
correlated to the beneficial influence of DF on the gut microbiome and mucosal surface (Sunkara 
et al., 2011). Again, the inclusion of β-glucan in the diets of pullets prevented the colonization oby 
Salmonella enteritidis in the visceral organs (Chen et al., 2008). The inclusion of butyrate in chick 
diets improved mucosal modulation, which led to a better growth performance and a lower 
colonization of Salmonella (Van Immerseel et al., 2004). The weights of the spleen, thymus and 
Bursa of Fabricus were increased in birds fed sodium-butyrate supplemented diets (Sikandar et al., 
2017). The thymus medulla and germinal centre area increased indicating a possible influence on 
the systemic immune system of the birds. Similarly, Eshak et al. (2016) observed an increase in 
bursa weights when broilers were treated with sodium butyrate. An effective interaction between 
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the immune system of monogastrics and the microflora of the gut maintains homeostasis and 
reduces the potential occurrence of diseases (Chassaing et al., 2014). 
2.7. Haematological response of broilers to wheat bran as a dietary fibre source in broiler 
diets 
The haematological status of a bird is an indication of its physiological, clinical and nutritional 
health condition (Olabanji et al., 2007). Largely, diets, drugs or environmental effects may 
influence the health status of the bird (Adamu et al., 2006). The haematological status refers to the 
numbers and morphology of blood cellular components and their calculated indices (Merck 
Manual, 2012). In feeding trials, haematological assessment reflects how test diets affect overall 
broiler performance, positively or adversely (Olabanji et al., 2007). When haematological values 
fall within the normal reference range, they indicate the test diet is nutritionally adequate to support 
all the required metabolism of the bird (Togun et al., 2007). Low or high values demonstrate either 
extremely high or inadequate amounts of some dietary components (Bawala et al., 2007). In a 
study by Idan, (2019), increasing levels of WB up to 12% did not have any adverse effect on the 
haematological indices of broilers. Furthermore, Martínez et al. (2015) reported no significant 
change in the levels of haemoglobin and haematocrit when up to 200g/kg WB was included in the 
diet of pullets. Also, the inclusion of 5% and 10% of neem kernel cake to broilers did not affect 
haematological indices apart from red blood cells (Frimpong, 2013).  
2.7.1. Blood haematological indices and what they imply 
The red blood cells (RBCs) are haemoglobin carriers and are involved in the transport of oxygen 
and carbon dioxide in the body (Waugh and Grant, 2001). Dietary protein levels, iron, copper, 
vitamin B2, B6, B12 and folic acid directly affect red blood cells (Nyaulingo, 2013). Low count 
of RBCs indicates a reduced amount of oxygen transport to the tissues as well as low transport of 
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carbon dioxide to the lungs for exhalation (Isaac et al., 2013). Blood haemoglobin is the protein 
pigment in RBCs that contains iron (Onyishi et al., 2017). It is significant in the diagnosis of 
anaemia and poor heart, liver or marrow function (Olagunju et al., 2013). Packed cell volume 
(PCV) or haematocrit (Ht/Hct) is the percentage of RBCs in the blood (Nyaulingo, 2013). It is 
related mainly to the transport of oxygen in the blood. A high Hct indicates an abnormal production 
of RBCs, dehydration or a reduced plasma volume (Chineke et al., 2006). A high or normal Hb 
and Hct is associated with a better feed conversion efficiency in broilers (Mitruka and Rawnsley, 
1977). The mean corpuscular volume (MCV) denotes the average volume of individual RBCs 
(Onyishi et al., 2017) A MCV value above the normal reference range implies a microcytic 
condition due to a larger shape of the RBCs. On the other hand, a lower MCV suggests the RBCs 
are smaller in shape (Jain, 1993). This parameter can be influenced by the environmental 
conditions or genotype of birds (Onyishi et al., 2017). Mean corpuscular haemoglobin (MCH) 
refers to the average mass of haemoglobin found in a red blood cell (Nyaulingo, 2013).  It is 
directly affected by the Hb count of the blood (Onyishi et al., 2017). Mean corpuscular 
haemoglobin concentration (MCHC) also indicates the levels of haemoglobin in an amount of 
packed red blood cells (Aster, 2004). Blood platelets are responsible for blood clotting. A low 
platelet concentration suggests a large amount of blood will be lost in case of injury (Merck 
Manual, 2012).  
The white blood cells (WBCs) are responsible for fighting infections through phagocytosis and 
the production of antibodies (Soetan et al., 2013). They are sustained by amino acids and they 
indicate how well the bird responds to stressful conditions (Lumeij, 1997).  An increase in WBC 
levels suggests the occurrence of inflammation, trauma or toxicity while a decrease reflects 
swelling or a chronic infection (Hidanah et al., 2018). White blood cells can be further categorized 
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into differentials, which add up to 100 – eosinophils, basophils, heterophils, lymphocytes and 
monocytes. Eosinophils are responsible for dealing with parasitic invasion and their effects 
(Irizaary-Rovira, 2004). Basophils respond to allergic reactions by secreting histamine and control 
antigen invasion (Vleck et al., 2000). Heterophils have antibacterial abilities and elevated levels 
of heterophils reflect the occurrence of leukaemia, parasitic or bacterial infections (Mitchell and 
Johns, 2008). However, in extreme cases of bacterial infections or haematopoietic cell diseases, 
heterophil counts are low (Latimer and Bienzle, 2000). Lymphocytes produce antibodies to fight 
chronic antigenic stimulations (Hidanah et al., 2018). The heterophil to lymphocyte (H: L) ratio is 
basically used as a stress indicator (Cotter, 2015). A higher percentage of monocytes in the blood 
indicates a large number of dead cells. Monocytes normally differentiate into macrophages and 
are responsible for phagocytosis, tissue repair, secretion of microbicidal factors, pro-inflammatory 
and anti-inflammatory cytokines (Abbas et al., 2014; Bayona et al., 2017). 
 
 
  
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CHAPTER THREE 
MATERIALS AND METHODS 
3.1. Experimental Site  
The trial was conducted at the Livestock and Poultry Research Centre (LIPREC), School of 
Agriculture, College of Basic and Applied Sciences, University of Ghana, Legon. LIPREC is 
located in the Greater Accra Region of Ghana, specifically on latitude 05040’N and longitude 
00016’W. It is about 8 km off the Legon-Aburi road from the ‘Ritz Junction’ at Madina and within 
the Coastal Savannah zone. LIPREC has a natural rangeland with mainly fire resistant shrubs, trees 
and tussock plants on it (Osei-Amponsah, 2010). Averagely, it has a temperature of 26.9°C but 
fluctuates between 24.8°C to 28.3°C in August and February respectively (Osei-Amponsah et al., 
2014). The research centre experiences a bimodal rainfall pattern comprising of major and minor 
seasons. The major season occurs between mid-March to July with the minor season occurring 
between mid-August to November. LIPREC has an annual rainfall range of 1280-1709 mm with 
a mean rainfall of 785 mm (Osei-Amponsah, 2014). At 1500 h, relative humidity is between 58 to 
83.7% but is slightly lower midmornings. 
 
3.2. Particle Size Analysis 
Particle size analysis was carried out at the Nutrition laboratory, Animal Science Department, 
School of Agriculture, University of Ghana. Samples of maize ground with a hammer mill fitted 
with 6 and 8 mm screens (Plate 3.1) were obtained and used for the analysis.  
 
 
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A: 6 mm screen B: 8 mm screen 
 
Plate 3. 1: Screens used in the milling of maize 
 
A Ro-tap sieve shaker (Model RX-29, W. S. Tyler Industrial Group, Mentor, OH) (Plate 3.2) which 
operates simultaneously by a mechanical and circular motion with a stack of sieves (13 in this 
case) that separates feed particles based on their sizes was used (Kalivoda et al., 2017). 
 
 
 
 
 
 
 
 
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Plate 3. 2: A Rotap machine with 7 sieves 
 
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The protocol for standard particle size analysis, ANSI/ASAE S319.4 as described by Kalivoda et 
al. (2017) was followed.  
Each sieve was weighed individually with sieve agitators (rubber balls and bristle sieve cleaners) 
to obtain a tare weight. Sieve agitators ensured the equal flow of the maize particles through the 
sieve openings (Table 3.1). Approximately 100g (± 5) of sample was weighed, mixed with 0.5g of 
dispersion agent (Model SSA-58, Gilson Company, Inc., Lewis Center, OH) and poured on the 
top sieve. The dispersion agent ensured uniform dispersion and prevented the maize particles from 
binding onto sieve screen surfaces. The sieve stack was then placed inside the Ro-tap machine and 
run for 15 minutes. 
Table 3. 1: Sieve and sieve agitator (s) arrangement 
U.S. sieve number Sieve opening (µm) Sieve agitator (s) 
6 3,360 None 
8 2,380 None  
12 1,680 3 rubber balls  
16 1,190 3 rubber balls  
20 841 3 rubber balls  
30 595 1 rubber ball; 1 bristle sieve cleaner 
40 420 1 rubber ball; 1 bristle sieve cleaner 
50 297 1 rubber ball; 1 bristle sieve cleaner 
70 210 1 rubber ball; 1 bristle sieve cleaner 
100 149 1 bristle sieve cleaner 
140 105 1 bristle sieve cleaner 
200 74 1 bristle sieve cleaner 
270 53 1 bristle sieve cleaner 
Pan - None 
(Kalivoda et al., 2017) 
 
 At the end of the run, the sieve stack was removed and each sieve weighed together with their 
sieve agitator (s). The weight obtained represented the residual sample, which was used to calculate 
the geometric mean diameter (dgw) and the geometric standard deviation (Sgw). Formulas as stated 
by Kalivoda et al., (2016) were used in these calculations.  
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3.3. Maize Particle Size Distribution 
The particle size distribution for maize samples ground using 6mm and 8mm screens are shown 
respectively in Figures 1 and 2. 
 The particle size of maize ground using a 6mm screen averaged 725μm with a geometric standard 
deviation (GSD) of 3.18μm. The highest proportions of the particle size distribution were retained 
on the 1700μm (17.23%) and 1800μm (18.80%) sieves. 
0.2
725μm ± 3.18μm 
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
3350 2360 1700 1180 850 600 425 300 212 150 106 75 53 37
Sieve opening, μm
Figure 3. 1: Particle size distribution of maize ground using a 6mm screen 
 
For maize ground using an 8mm screen, most particles were collected on the 2360μm (20.58%) 
and 1700μm (17.43%) sieves.  
The geometric mean average was 1178μm with a geometric standard deviation (GSD) of 3.07μm.  
 
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Retained particles on sieves, %
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0.25
1178μm ± 3.07μm
0.2
0.15
0.1
0.05
0
3350 2360 1700 1180 850 600 425 300 212 150 106 75 53 37
Sieve opening, μm 
Figure 3. 2: Particle size distribution of maize ground using an 8mm screen 
 
These maize particle sizes ranges were used in the formulation of the experimental diets. 
3.4. Experimental Diets  
In this trial, wheat bran was used as the dietary fibre source and its inclusion increased among 
treatments and per phase (Table 3.2). 
During the brooding period (one week), a common broiler starter was fed to all birds, which 
contained 8% wheat bran (WB) with fine maize particles. Subsequently, six dietary treatments 
were fed in a two-phase feeding regime comprising of a starter (three weeks) and finisher (three 
weeks) phase (Tables 3.2). To create the experimental treatments concerning the two different 
maize particle sizes, treatment 1 (T1), treatment 2 (T2) and treatment 3 (T3) were processed to 
contain fine maize particles whereas treatment 4 (T4), treatment 5 (T5) and treatment 6 (T6) 
contained coarse maize particles. These particle sizes were maintained for both phases.  
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Retained particles on sieves, %   
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During the starter phase, T1, T2 and T3 were formulated to contain 6, 8 and 10%WB. The WB 
inclusion rate for treatments 4, 5 and 6 followed the same inclusion rate as T1, T2 and T3. With 
the finisher phase, T1 and T4 contained 13% WB with T2 and T5 containing 15% WB. Treatments 
3 and 6 were formulated to contain 17% WB.  
 
Table 3. 2: Experimental diets 
  Level of wheat bran (%) 
Treatment Particle size Starter  Finisher 
(μm) 
1 Fine 6 13 
2 Fine 8 15 
3 Fine 10 17 
4 Coarse 6 13 
5 Coarse 8 15 
6 Coarse 10 17 
 
All diets were formulated to meet the recommended broiler nutrient requirements according to 
Cobb 500 specifications (Cobb 500, 2018). In addition, the dietary treatments were in a mash form 
and formulated to be isonitrogenous and isocaloric. The composition, calculated nutrient contents 
and analysed chemical composition of dietary treatments are shown in Table 3.3 and 3.4. 
 
3.5. Experimental Birds, Experimental Design and Housing 
A total of three-hundred-day-old mixed sex broiler chicks were obtained from a prominent 
commercial hatchery. 
 
 
 
 
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Wheat Table 3. 3: Percentage composition of the dietary treatments fed during the starter phase (day 
one to day 21) 
 Treatment 
Ingredients (%) T1 T21 T3 T4 T5 T6 
6%WB 8%WB 10%WB 6%WB 8%WB 10%WB 
+Fine +Fine +Fine +Coarse +Coarse +Coarse 
Wheat bran 6.00 8.00 10.00 6.00 8.00 10.00 
Maize 55.50 52.60 49.70 55.50 52.60 49.70 
Soybean meal 36.00 35.90 35.80 36.00 35.90 35.80 
Salt 0.50 0.50 0.50 0.50 0.50 0.50 
Oyster shell 0.55 0.55 0.55 0.55 0.55 0.55 
L-Lysine 0.15 0.15 0.15 0.15 0.15 0.15 
DL-Methionine 0.15 0.15 0.15 0.15 0.15 0.15 
Dicalcium phosphate 0.20 0.20 0.20 0.20 0.20 0.20 
Toxin binder 0.20 0.20 0.20 0.20 0.20 0.20 
Broiler premix2 0.25 0.25 0.25 0.25 0.25 0.25 
Vegetable oil 0.50 1.50 2.50 0.50 1.50 2.50 
Total 100.00 100.00 100.00 100.00 100.00 100.00 
Calculated analyses       
ME3 (MJ/kg) 3218.7 3218.3 3217.9 3218.7 3218.3 3217.9 
Crude protein (%) 23.22 23.22 23.23 23.22 23.22 23.23 
Analysed composition      
Dry matter (%) 86.66 87.79 86.72 87.02 86.17 86.71 
CP (% of DM)4 26.63 26.69 27.15 26.73 27.05 27.10 
CF (% of DM)5 3.14 3.19 3.44 3.17 3.50 3.75 
EE (% of DM)6 4.51 4.46 4.21 4.37 4.49 4.49 
Ash (% of DM)7 4.10 4.16 2.27 3.61 2.12 3.74 
1Control diet 
2Vitamin premix supplied the following kilogram per diet: vit A, 10,000 IU; vit D3, 2000 IU; vit E, 10 IU; 
vit K, 3 mg; riboflavin, 4.4 mg; cobalamin, 0.05 mg; pantothenic acid, 8 mg; niacin, 16.5 mg; choline, 175 
mg; folic acid, 0.5 mg; Mg, 2.3 mg; Fe, 30.5 mg; Zn, 50 mg; Co, 0.27 mg. 
3Metabolizable energy 
 
These were assigned to six treatment diets. There were five replications, ten birds per replicate and 
fifty birds per treatment. The experiment was set up in a 2 x 3 factorial arrangement to access the 
interactive effects between maize particle sizes (fine/coarse) and levels of fibre (wheat bran) 
inclusion [(starter: 6, 8 and 10%; finisher: 13, 15 and 17%)] in broilers. The birds were completely 
randomized into thirty wire mesh-sided concrete floor pens (ten birds per pen) with short walls 
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measuring about 2ft walls. The dimensions for each pen were 1m x 1m, hence, each pen had a 
stocking density of one bird per 0.1m2. 
 
Table 3. 4: Percentage composition dietary treatments fed during the finisher phase (day 22 to day 
42) 
 Treatment (kg) 
Ingredients (%) T1 T21 T3 T4 T5 T6 
13%WB 15%WB 17%WB 13%WB 15%WB 17%WB 
+Fine +Fine +Fine +Coarse +Coarse +Coarse 
Wheat bran 13.00 15.00 17.00 13.00 15.00 17.00 
Maize 59.00 56.10 53.20 59.00 56.10 53.20 
Soybean meal 25.00 24.90 24.80 25.00 24.90 24.80 
Salt 0.50 0.50 0.50 0.50 0.50 0.50 
Oyster shell 0.55 0.55 0.55 0.55 0.55 0.55 
L-Lysine 0.15 0.15 0.15 0.15 0.15 0.15 
DL-Methionine 0.15 0.15 0.15 0.15 0.15 0.15 
Dicalcium phosphate 0.20 0.20 0.20 0.20 0.20 0.20 
Toxin binder 0.20 0.20 0.20 0.20 0.20 0.20 
Broiler premix2 0.25 0.25 0.25 0.25 0.25 0.25 
Vegetable oil 1.00 2.00 3.00 1.00 2.00 3.00 
Total 100.00 100.00 100.00 100.00 100.00 100.00 
Calculated analyses       
ME3 (MJ/kg) 3123 3122 3122 3123 3122 3122 
Crude protein (%) 19.35 19.36 19.36 19.35 19.36 19.36 
Analyzed composition      
Dry matter (%) 87.22 86.42 86.96 87.65 86.85 87.56 
CP (% of DM)4 23.43 22.19 22.89 23.63 22.24 23.71 
CF (% of DM)5 4.20 4.50 4.78 4.48 4.54 4.80 
EE (% of DM)6 4.17 4.44 4.24 3.18 4.02 4.28 
Ash (% of DM)7 5.12 3.60 4.42 4.78 4.54 4.55 
1Control diet 
2Vitamin premix supplied the following kilogram per diet: vit A, 10,000 IU; vit D3, 2000 IU; vit E, 10 
IU; vit K, 3 mg; riboflavin, 4.4 mg; cobalamin, 0.05 mg; pantothenic acid, 8 mg; niacin, 16.5 mg; choline, 
175 mg; folic acid, 0.5 mg; Mg, 2.3 mg; Fe, 30.5 mg; Zn, 50 mg; Co, 0.27 mg. 
3Metabolizable energy 
 
3.6. Management of Experimental Birds  
Day-old broiler chicks (Cobb 500; initial average body weight, 43.86g) were brooded for one 
week, which served as an acclimatization period (Plate 3.3). Antibiotics and vitamins were 
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administered through water for two days and a common starter diet was fed for the brooding 
period. Coal-heated clay pots served as a source of heat for the chicks during the brooding period. 
Individual chick weights at d7 (between 151 – 207g; average weight, 180g) were used as a baseline 
to aid in the allocation of the birds to randomized pens.  
 
 
 
 
 
 
 
 
A: Set-up for brooding period B: Birds at brooding period 
 
Plate 3. 3: Brooding period 
 
At the start of the experiment, each pen was filled with new wood shavings. These shavings were 
changed periodically in order to maintain good hygiene. A plastic feeding tube and waterer were 
placed in each pen. Birds had ad-libitum access to clean water and feed throughout the experiment. 
The birds in each replicate (experimental unit) were collectively fed pre-determined amounts of 
feed. The feeders were shaken at least once a day. Sunlight and electric lamps served as sources 
of light. The temperature of the house was maintained at 32 oC to 33oC, 29oC and 27oC from day 
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1 to day 7, day 8 to day 14 and day 15 to day 42 respectively. Standard vaccinations and all 
recommended prophylactic measures were duly followed throughout the entire period. Birds were 
vaccinated such Newcastle and Gumboro with medications such as coccidiostat being provided. 
3.7. Data Collection 
3.7.1. Growth Trial 
The growth trial lasted 42 days. Initial and weekly body weights (BW) (d0, 7, 14, 21, 28, 35 and 
42) of birds per pen (10 birds) were taken and used to calculate average daily gain (ADG) using 
formula A.  
A. 
Total body weight gained
ADG (g) =  
Number of days × Number of birds in a pen
 
Weekly amounts of feed given and feed refused were recorded and used in the computation of feed 
disappearance and average daily feed intake (ADFI) using formula B.  
B. 
Total amount of feed offered − residual feed
ADFI (g) =  
Number of days × Number of birds in a pen
 
Feed conversion ratio was calculated by dividing ADFI by ADG of broilers (c). Mortalities were 
recorded daily and used to adjust feed conversion ratio. 
C. 
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ADFI
FCE =  
ADG
Finally, percentage mortality (P.E.) was calculated using formula D. 
 
D.  
Total number of dead birds
P. E. (%) = { } x100 
Total number of experimental birds
 
3.7.2. Carcass Characteristics Analysis and Caecal pH Measurement 
At the end of the experiment (day 43), one bird of average body weight in each pen (replicate) was 
randomly selected (five birds per treatment) for carcass traits and caecal pH measurement.  
On day 43 the live weight of each bird was taken and recorded as the final weight. Birds were 
slaughtered by the severance of the carotid arteries and allowed to bleed out completely, then 
defeathered. Defeathered weights of the birds were taken after which organs of interest were 
harvested and weighed. Weights of organs such as the gizzard, crop, intestines, kidney, liver, 
thymus and spleen were taken. After the removal of the viscera, the weights of the carcass, breast, 
thigh and wings were also recorded. 
The caeca of each bird were excised and their contents pooled into a container. The pH of the 
caecal content was measured using a Milwaukee SM101 pH meter. 
3.7.3. Blood Sampling  
On day 43, five birds (one per replicate) of average weight from each treatment were selected for 
the determination of haematological profile and glucose levels. Two mls of blood was drawn from 
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wing vein using a sterile needle into Ethylene diamine tetra acetic acid (EDTA) vacutainer tubes. 
Blood samples were placed on ice and transported to the laboratory for blood analysis.  
3.7.3.1. Determination of Haematological Indices 
The URIT-5250Vet Haematology Analyzer was used in determining/calculating the following 
blood parameters: red blood cells (RBC), haemoglobin (HGB), haematocrit (HcT), mean 
corpuscular volume (MCV), mean cell haemoglobin (MCH) and mean cell haemoglobin 
concentration (MCHC).   
3.7.3.2. Differential White Cell Count  
Relative percentages of the various white blood cells (basophils, eosinophils, lymphocytes, 
monocytes and heterophils) present in the blood samples were determined manually. The protocol 
of Evatt et al. (1992) was used. A thin smear of a homogenous blood sample was made on a clean 
slide and waved to air dry. One volume of Leishman stain (for 1-2 minutes) and two volumes of 
buffered water (5-7 minutes) were applied on the smear consecutively and allowed to stand. The 
slide was then washed in excess buffer and allowed to stand for 2 minutes for effective 
differentiation. A drop of oil was used to mark a portion on the slide and the differential counting 
in 100 white blood cells was done using an oil immersion objective lens (40X) of a light 
microscope. 
3.7.3.3. Serum Glucose Determination 
Drops of blood from each bird were used to determine their glucose level using a Gold-Accu Blood 
Glucose Monitoring system (Changsha Sinocare Inc., China). 
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3.7.4. Gut morphological analysis 
After blood collection, birds were exsanguinated and allowed to bleed thoroughly from the jugular 
veins. Abdominal cavities were opened and their small intestines removed. Portions of the jejunum 
and ileum were taken for the analysis of intestinal morphological changes.  
Tissues from the jejunum (extends from pancreo-billiary duct to Meckel’s diverticulum) and ileum 
(extends from the Meckel’s diverticulum to the ileo-caecal valve) were taken from each bird. 
Samples were flushed, injected with 10% neutral formalin and immediately placed in containers 
filled with appropriate amount of fixative. This fixation step was necessary to preserve and protect 
the integrity of the tissues. Further intestinal morphometric examination was then carried out on 
the samples. The protocol of Hair bin Bejo (1990) was followed. The jejunal and ileal samples 
were sliced with a microbiome blade to display their mucosal surface. The formalin was then 
washed off by placing sliced samples under running water for about 30 minutes. The formalin-free 
samples were then dehydrated by immersing them in a series of ethanol solutions with increasing 
concentrations (70, 80, 90 and 100%) at an interval of 15 minutes each. Ileal and jejunal tissues 
were then immersed in 100% ethanol at intervals of 30 and 45 minutes apart. Tissue samples were 
further soaked in xylene, an intermediate solvent, at 20, 20 and 45 minutes apart, which enabled 
infiltration of molten paraffin wax at 60°C. The waxed samples were kept overnight and allowed 
to cool to solidification at 20°C. Using an ‘embedding centre’, the intestinal samples were blocked 
and sectioned at 6 μm thickness, at an angle of 5o using a microbiome.  Sections were fixed on glass 
slides, heated on water (40oC) to dryness and deparaffinized. They were then stained with 
haematoxylin and eosin and mounted on histological slides with cover slips. Using a binocular light 
microscope with a ToupView camera adaptor, the slides were examined. The villi height and crypt 
depth were then read using a binocular light microscope with a ToupView camera adaptor. The villi 
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height to crypt depth ratio was also calculated. Values from three well-oriented villi and crypts of 
each bird were measured in micrometres and the average taken. 
3.7.5. Analysis of Caecal Short-Chain Fatty Acids Concentrations 
Again, after the blood sampling, the caecal contents of the birds were pooled together per replicate 
and used for the analysis of short-chain fatty acid concentrations. The short-chain fatty acids 
(SCFAs) that were analysed included acetic, propionic and butyric acids. Caecal contents of the 
individual birds were gently squeezed into well labelled Eppendorf tubes and immediately placed 
on ice for transportation to the laboratory Samples were stored at 40C. Stock solutions of acetic, 
propionic and butyric acid were prepared at a concentration of 1000 mg/ml in 0.4% hydrochloric 
acid solution (HCL). Serial dilution was carried out for each standard to obtain five concentrations 
(100, 50, 25, 12.5 and 6.25 µg/ml) separately prior to HPLC analysis. Accurately, 0.5g of the 
caecal content were weighed into a tube and thoroughly mixed with 5mL of 0.4% HCL. The 
mixture was initially centrifuged at 4000rpm for 30 minutes and at 10,000rpm for 15 minutes. 
After the separation, the supernatant was loaded into an HPLC vial for analysis. 
Short-chain fatty acids concentrations were determined in caecal samples using the principle of 
high-performance liquid chromatography-ultraviolet detection (HPLC). The protocols of Reuter 
(2015) and Kim (2016) were followed. The HPLC analysis was carried out using an Agilent 1100 
system (Santa Clara, CA, USA), composed of degasser, quaternary pump, auto sampler, diode 
array detector (DAD), and HP ChemStation Software. Chromatographic separation was carried 
out on an ODS C18 (250 x 4.6 mm id., 5 μm particle size) analytical column maintained at 300C, 
20 µL injection volume and the wavelength monitored at 254nm. The reverse phase principle of 
HPLC was applied in the chromatographic separation. The mobile phase consisted of A: 10mM 
KH2PO4, which was adjusted to a pH of 2.4 using phosphoric acid and B: Acetonitrile. Table 3.5 
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shows the gradient time program used for the analysis. With the retention time and peak area 
generated, standard curves for acetic, propionic and butyric acid were obtained which served as a 
baseline for the determination of SCFAs levels in the caecal samples expressed in μg/g. 
 
Table 3. 5: Gradient time program for HPLC analysis 
Time  Flow rate %A1 %B2 
(minutes) (mL/min) 
0.0 1 80 20 
10.0 1 40 60 
12.5 1 40 60 
12.6 1 80 20 
15.0 1 80 20 
1Moble phase A: 10-mM KH2PO4 
2Mobile phase B: Acetonitrile 
 
3.7.6. Microbial Population 
The counts of Lactobacillus spp. and E. coli in caecal samples were analysed. Approximately 1g 
of the caeca contents were emptied in well-labelled sterile containers and stored at 40C pending 
further analysis. The modified protocol of Hu and Guo (2007) was followed. 
From each sample, 0.1g was weighed into sterile containers and diluted in a 1:10 ratio with saline 
solution (sodium chloride). Further serial dilutions (10-2 – 10-9) were carried out on the resulting 
homogenate using saline solution as a diluent. One hundred microliters of each homogenate per 
sample was plated on sterilized agar plates. Lactobacillus spp. were cultured on de man, Rogosa, 
Sharpe (M.R.S.) agar (CM0361, Oxoid LTD., Basingstoke, Hampshire, England) with the 
following components: peptone 10.0; ‘Lab-Lemco’ powder 8.0; yeast powder 4.0; Glucose 20.0; 
Sorbitan mono-oleate 1ml; Di-potassium hydrogen phosphate 2.0; Sodium acetate 2H2O 5.0; Tri-
ammonium citrate 2.0; Magnesium sulphate 7H2O 0.2; Manganese sulphate 4H2O 0.05 and agar 
10.0. E. coli growth was measured on Eosin methylene blue (E.M.B.) agar (M317-500G, HiMedia 
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Laboratories Pvt. Ltd., India) made up of: peptic digesta of animal tissue 10.00; Dipotassium 
phosphate 2.00; lactose 5.00; sucrose 5.00; eosin –Y 0.40; methylene blue 0.065 and agar 13.50. 
Lactobacillus spp. agar plates were incubated anaerobically at 350C while E. coli agar plates were 
incubated at 440C. Countable colonies were recorded and expressed as log10 cfu/g.  
3.7.7. Apparent Nutrient Digestibility Trial 
Three birds (replicates) from each treatment (18 birds in total) were selected and used for a one-
week digestibility trial. Each bird was placed in a clean and well- labelled metallic battery cage 
equipped with a nipple drinker and a feeding trough. An adaptation period of 4 days was allowed, 
followed by a withdrawal of feed for 12 hours. On the 5th, 6th and 7th days, birds were given 250g 
(average daily feed intake) of their respective diets while water was provided ad-libitum. For three 
consecutive days, total excreta collection was done after every 24-hour period (0800 h – 0800 h) 
and the excreta immediately frozen at -200C for further analysis. Daily refusals were recorded and 
used to compute daily feed intake. At the end of the 7th day, daily excreta samples of each replicate 
were thawed, pooled, and weighed. Samples were then dried at 550C in an air-flow type oven for 
five days followed by chemical analysis. The total tract apparent nutrient digestibility was 
calculated using the digestibility formula by Adeola (2000) as:  
Digestibility, % = 100 X Component intake – Component faeces 
      Component intake 
 
 
3.8. Economics of Production 
A feed cost analysis was carried out on all treatments based on the cost of individual feed 
ingredients (Table 3.6). Parameters such as cost of feed per kilogram (GH₵), total cost of feed 
consumed (GH₵), and total cost of feed per kilogram weight gain (GH₵), were calculated. Feed 
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costs per kg for each of the experimental diets were calculated based on the prevailing prices of 
the ingredients at the time of the experiment. 
Table 3. 6: Cost of feed ingredients on a per kilogram basis 
Ingredient Weight per bag (kg) Cost per bag (GH¢) Cost per kilogram (GH¢) 
Wheat bran 25 16.5 0.66 
Maize 50 85 1.7 
Soybean meal 50 140 2.8 
Dicalcium phosphate 25 95 3.8 
Oyster shell grit 50 25 0.5 
Salt 50 40 0.8 
Lysine 25 240 9.6 
Methionine 25 500 20 
Broiler premix 25 200 8 
Toxin binder 25 190 7.6 
Oil 24 165 6.88 
 
3.9. Chemical Analysis 
Representative feed and excreta samples were finely ground with a Retsch mill (Model ZM200, 
Retsch GmbH, Retsch-Allee 1-5, Haan Germany) fitted with a 0.5 mm sieve. Each sample was 
subjected to proximate analysis according to the Association of Official Analytical Chemist 
(AOAC, 1984) procedures to determine the dry matter (DM), crude protein (CP), ether extract 
(EE), crude fibre (CF) and acid-insoluble ash contents. The nitrogen free extract (NFE) was 
calculated using the formula: 
                        NFE= DM% - (CP% + CF% + Ash% + CF %) 
3.10. Statistical Analysis 
All data gathered were subjected to statistical analysis using the Generalized Linear Mixed Model 
(GLIMMIX) procedure of the Statistical Analysis System Institute (SAS) version 9.4 (SAS 
Institute, 1994). The main and interactive effects of particle size and levels of wheat bran on the 
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parameters mentioned were assessed. Significant mean differences were separated using Tukey’s 
test at a 5% probability level. 
 
 
 
 
 
  
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CHAPTER FOUR 
RESULTS  
4.1. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Mortality 
At the end of the experimental period, 17 mortalities out of 300 birds were recorded. This 
amounted to an overall percentage mortality of 5.67%. No evidence of treatment-related effects 
were observed. Post mortem autopsies carried out indicated yolk sac infection and chronic 
respiratory tract disease as causes of observed mortalities. 
4.2. Effect of dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Apparent Nutrient Digestibility 
The digestibility coefficients for dry matter (DM), organic matter (OM) and crude protein (CP) are 
shown in Table 4.1. The digestibility coefficients of DM, OM and CP averaged 74.86, 43.15 and 
70.15% across treatments. No main or interactive effect between WB level and maize particle size 
on any of the parameters were observed. 
4.3. Effect of dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Overall Growth Performance (day one to day 42) 
Table 4.2 shows the effect of dietary fibre level (using wheat Bran as a DF source) and maize 
particle size on growth performance from day 1 to day 42. A WB level effect (p=0.02) was 
observed on ADFI by day 42. The ADFI of birds on diets with 6/13%WB (104.55g) and 
10/17%WB (104.64g) was significantly higher (p≤0.05) than that of birds on 8/15%WB (94.90g). 
In addition, a significant effect (p≤0.05) on ADFI caused by an interaction between the WB level 
effect and maize particle size was observed.  
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Table 4. 1:Effect of dietary fibre level (using wheat Bran as a DF source) and maize 
particle size on dry matter, organic matter and crude protein digestibility 
Treatment %Wheat bran Maize  % 
Starter Finisher particle size Dry matter Organic matter Crude protein 
T1 6 13 Fine 73.61 32.82 69.54 
T2 8 15 Fine 74.83 45.48 70.23 
T3 10 17 Fine 74.05 46.30 71.00 
T4 6 13 Coarse 74.15 45.88 68.97 
T5 8 15 Coarse 81.28 51.28 74.08 
T6 10 17 Coarse 71.22 37.13 67.07 
Pooled SEM1   4.52 6.08 4.01 
                                                                                Main effect 
%Wheat bran     
 Starter Finisher     
 6 13  73.88 39.35 69.26 
 8 15  78.06 48.38 72.15 
 1 0 17  72.64 36.71 69.04 
SEM   2.26 4.30 2.84 
Maize particle size      
    Fine 74.16 41.54 70.26 
    Coarse 75.55 41.43 70.04 
SEM     1.85 3.50 2.32 
Source of variation P-value 
Wheat bran * Maize particle size 0.37 0.06 0.63 
Wheat bran   0.25 0.17 0.69 
Maize  particle size   0.60 0.98 0.95 
SEM1: Standard error of means 
 
Feed intake of birds on T4 [(coarse + 6/13%WB); 107.15g] and T6 [(coarse + 10/17%WB); 
106.73g] was significantly higher (p≤0.05)  that that of birds on T5 [(coarse + 8/15%WB); 89.29g] 
but similar (p≥0.05) to that of birds on T1 [(fine + 6/13%WB); 101.96g], T2 [(fine + 8/15%WB); 
100.49g] and T3 [(fine + 10/17%WB); 102.55g]. 
  
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Table 4. 2: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle size on 
overall growth performance (day 1 to day 42) 
   Grams 
Treatment %Wheat bran Maize particle Average daily Average  Feed  Final body  
Starter Finisher size feed intake daily gain conversion ratio weight 
T1  6 13 Fine 101.96ab 57.17 1.81ab 2578.4 
T2 8 15 Fine 100.49ab 57.25 1.76ab 2612.3 
T3 10 17 Fine 102.55ab 54.58 1.90b 2519.5 
T4 6 13 Coarse 107.15a 60.01 1.78ab 2695.9 
T5 8 15 Coarse 89.29b 54.64 1.66a 2531.8 
T6 10 17 Coarse 106.73a 60.66 1.77ab 2726.0 
Pooled SEM1  3.67 2.20 0.05 100.34 
                                                                               Main effect 
%Wheat bran      
 Starter Finisher       
 6 13 a 104.55  58.59 1.79 2637.2 
 8 15  94.90
b 55.95 1.70 2572.0 
 1 0 17  104.64
a 57.62 1.83 2622.8 
SEM 2.49 1.63 0.04 107.60 
Maize particle size 
  
  Fine 101.67 56.33 1.82
b 2570.1 
  Coarse 101.06 58.44 1.73
a 2651.3 
SEM 2.12 1.39 0.03 63.46 
Source of variation  P-value 
Wheat bran * Maize particle size 0.05 0.20 0.04 0.41 
Wheat bran 0.02 0.55 0.07 0.82 
Maize particle size 0.84 0.30 0.05 0.38 
SEM1: Standard error of means; Means in a column with different superscripts are significantly different at  
p ≤ 0.05 
 
There were no main or interactive effect (p≥0.05) between WB level and maize particle size on 
ADG and BW throughout the experimental period. However, maize particle size effect on FCR 
was significant (P=0.05) on FCR with birds fed coarse maize particles (1.73) being the most 
efficient in converting feed to gain as compared to birds fed fine maize particle sizes (1.82). In 
addition, a significant response (P=0.04) to the interaction between WB level and maize particle 
size on FCR was observed. Birds on T5 (1.66) were the most efficient in converting feed to gain 
at the end of the trial. Their FCR performance was similar (p≥0.05) to that of birds T1 (1.81), T2 
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(1.76), T4 (1.78) and T6 (1.77) but higher (p≥0.05) than that of birds T3 (1.90). Figures 4.1, 4.2 
and 4.3 illustrates the trend in ADFI, ADG and FCR from day 0 to day 42. 
180
160
140
120
100
80
60
40
20
0
1 2 3 4 5 6
Weeks
T1 (Fine + 6/13%WB) T2 (Fine + 8/15%WB)
T3 (Fine + 10/17%WB) T4 (Coarse + 6/13%WB)
T5 (Coarse + 8/15%WB) T6 (Coarse + 10/17%WB)
Figure 4. 1: Trends in average daily feed intake 
 
90
80
70
60
50
40
30
20
10
0
1 2 3 4 5 6
Weeks
T1 (Fine + 6/13%WB) T2 (Fine + 8/15%WB)
T3 (Fine + 10/17%WB) T4 (Coarse + 6/10%WB)
T5 (Coarse + 8/15%WB) T6 (Coarse + 10/17%WB)
Figure 4. 2: Trends in average daily gain 
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3
2.5
2
1.5
1
0.5
0
1 2 3 4 5 6
Weeks
T1 (Fine + 6/13%WB) T2 (Fine + 8/15%WB)
T3 (Fine + 10/17%WB) T4 (Coarse + 6/13%WB)
T5 (Coarse + 8/15%WB) T6 (Coarse + 10/17%WB)
Figure 4. 3: Trends in feed conversion ratio 
  
4.4.1. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle 
Size on Growth Performance during the Starter Phase (day one to day 21) 
The effect of diet on growth performance of during the starter phase is presented in Table 4.3. No 
WB level or maize particle size effect was observed on ADFI, ADG, FCR and BW by day 21. On 
the other hand, a significant interaction (p≤0.05) between WB level and maize particle size was 
observed on ADG, FCR and BW at the end of the starter phase. Birds on T4 [(coarse + 6%WB); 
48.81g] were the heaviest (p≤0.05) with birds on T5 [(coarse + 8%WB); 40.57g] having the least 
weight gain. The ADG values of T1 [(fine + 6%WB); 44.02g), T2 [(fine + 8%WB); 45.65g], T3 
[(fine + 10%WB); 44.88g] and T6 [(coarse + 10%WB); 45.23g] were similar (p≥0.05) to that of 
T4. 
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Also, birds on T4 (1.56) converted feed to gain efficiently during the starter phase and their 
performance was similar (p≥0.05) to that of birds on T1 (1.85), T2 (1.73), T5 (1.83) and T6 (1.82) 
but higher (p≤0.05) than that of birds on T3 (1.86). The interactive effect on BW (p=0.04) followed 
a similar trend as that of ADG and FCR with birds on T4 (1215.94g) and T2 (1152.00g) having 
the highest BW with birds on T5 (1057.60g) having the lowest.  
 
Table 4. 3: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle size on 
growth performance during the starter phase (day 1 to day 21) 
   Grams 
Treatment %Wheat  Maize particle Average daily Average daily Feed conversion  Body 
Bran size feed intake gain Ratio weight 
T1  6 Fine 84.53 44.02ab 1.85ab 1104.6ab 
T2 8 Fine 79.06 45.65ab 1.73ab 1152.0a 
T3 10 Fine 84.83 44.88ab 1.86b 1128.4ab 
T4 6 Coarse 78.71 48.81a 1.56a 1215.9a 
T5 8 Coarse 76.26 40.57b 1.83ab 1057.6b 
T6 10 Coarse 85.00 45.23ab 1.82ab 1131.5ab 
Pooled SEM1  3.45 1.60 0.08 34.42 
                                                                        Main effect 
%Wheat bran       
 6  81.62 46.41 1.71 1160.3 
 8  77.66 43.11 1.78 1103.5 
  10  84.92 45.05 1.84 1130.0 
SEM 3.45 1.13 0.05 36.91 
Maize particle size 
  
  Fine 82.81 44.85 1.82 1128.3 
 C oarse 79.99 44.87 1.74 1134.1 
SEM 1.99 0.92 0.04 21.77 
Source of variation P-value 
Wheat bran * Maize particle size 0.70 0.02 0.04 0.04 
Wheat bran 0.13 0.14 0.22 0.35 
Maize particle size 0.33 0.99 0.21 0.85 
SEM1: Standard error of means; Means in a column with different superscripts are significantly different at 
p ≤ 0.05 
  
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4.4.2. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle 
Size on Growth Performance during the Finisher Phase (day 22 to day 42) 
The effect of WB level and maize particle size on growth performance during the finisher phase is 
shown in Table 4.4.  Maize particle sizes were kept constant with WB level increasing from 6, 8 
and 10% to 13, 15 and 17%. On an average, the ADFI, ADG, FCR, BW values across treatment 
were 120.99g, 69.64g, 1.78 and 2610.67g respectively. The values obtained on growth 
performance of birds during the finisher phase were comparable (p≥0.05) with no WB level, maize 
particle size or interactive effects being observed. 
Table 4. 4: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle 
size on growth performance during the finisher phase (day 22 to day 42) 
   Grams 
Treatment %Wheat  Maize particle Average daily Average daily Feed conversion  
Bran size feed intake gain Ratio 
T1  13 Fine 119.39 70.32 1.76 
T2 15 Fine 121.93 68.86 1.79 
T3 17 Fine 120.26 64.28 1.93 
T4 13 Coarse 130.75 70.53 1.93 
T5 15 Coarse 105.14 67.79 1.57 
T6 17 Coarse 128.46 76.08 1.72 
Pooled SEM1  5.82 3.89 0.11 
                                                                      Main effect 
%Wheat bran      
 13  125.07 70.43 1.84 
 15  113.54 68.33 1.68 
 1 7  124.36 70.18 1.83 
SEM 4.31 2.88 0.08 
 Maize particle  size     
  Fine 120.53 67.82 1.83 
  Coarse 121.45 71.47 1.74 
SEM 3.67 2.46 0.06 
Source of variation P-value 
Wheat bran * Maize particle size 0.07 0.27 0.16 
Wheat bran 0.14 0.86 0.26 
Maize particle size 0.86 0.31 0.34 
SEM1: Standard error of means    
  
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4.5. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Relative Weights of Carcass Parameters 
The effects of dietary treatments on carcass parameters are presented in Tables 4.5. By day 42, the 
average live, de-feathered and dressed weights of experimental birds were 3070.00, 2791.67 and 
2309.67g with no WB level or maize particle size been observed (P≥0.05). 
Table 4. 5: Effect of dietary fibre level (using wheat Bran as a DF source)  and maize particle size on relative 
weights of carcass parameters 
    grams %1 
Trt2 %WB3 PS6 Live Defeat.7 Dressed Breast Back Wings Thighs Drum Abd.8 
S4 Fi5 weight weight weight -sticks fat 
T1  6 13 F9 3084.0 2800.0 2356.0 37.09 18.01 10.03 13.24 12.14 0.53 
T2 8 15 F 3026.0 2748.0 2342.0 36.27 18.25 10.07 13.69 12.26 0.57 
T3 10 17 F 3224.0 2626.0 2252.0 35.57 19.32 10.96 14.43 12.61 0.58 
T4 6 13 C10 3030.0 2988.0 2206.0 34.10 18.52 10.81 14.36 13.13 0.69 
T5 8 15 C 2892.0 2678.0 2248.0 33.14 18.98 11.05 14.72 13.03 0.78 
T6 10 17 C 3164.0 2910.0 2454.0 35.14 17.51 10.79 14.51 12.75 0.70 
Pooled SEM11 173.66 96.93 209.85 28.13 13.78 7.10 10.09 8.53 0.87 
Main effect 
%Wheat bran  
 S Fi            
 6 13  3057.00 2894.00 2231.00 34.68 18.50 10.42 14.10 12.64 0.65 
 8 15  2959.00 2713.00 2295.00 34.70 18.61 10.56 14.21 12.65 0.67 
 10 17  3194.00 2768.00 2353.00 35.35 18.42 10.87 14.47 12.68 0.64 
SEM  122.80 68.54 148.39 19.89 9.74 5.02 7.14 6.03 0.61 
M aize p article size         
   F
 3111.33 2724.67 2269.33 36.31 18.53 10.36 13.79 12.34 0.56 
 C  3028.67 2858.67 2316.67 54.34 29.86 16.34 22.42 19.63 1.45 
SEM 100.26 55.97 121.16 16.24 7.96 4.10 5.83 4.93 0.50 
Source of variation  P-value 
WB * PS  0.97 0.19 0.56 0.49 0.34 0.41 0.40 0.39 0.37 
Wheat bran 0.41 0.18 0.85 0.46 0.38 0.45 0.45 0.42 0.40 
Maize particle size 0.57 0.10 0.78 0.44 0.32 0.32 0.31 0.31 0.22 
%1: Absolute weights were expressed as percentage of dressed weight; Trt2: Treatment; WB3 Wheat bran; S4: 
Starter; Fi5: Finisher; PS6: Maize particle size; Defeat7: Defeathered; Abd8: Abdominal fat; F9: Fine; C10: Coarse; 
SEM11: Standard error of the means 
 
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Furthermore, no interactive or main effects (p≥0.05) were observed on the relative weights of the 
breast, back, wings, thighs and drumsticks of all birds. No WB level (p=0.40) or maize particle 
size (p=0.22) effect on relative abdominal fat weight was observed. 
4.6. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Relative Organ Weights 
The full and empty intestines, empty crop, full proventriculus, full gizzard, heart and liver of 
experimental birds were not significantly (p≥0.05) affected by the level of WB and maize particle 
size as shown in Table 4.6. On the other hand, there was a significant interaction (p=0.02) between 
the level of WB and maize particle size on relative empty gizzard weight of birds. Birds on T4 
[(coarse + 6/13%WB); 2.00%] had heavier empty gizzards (p≤0.05) than birds on T1 [(fine + 
6/13%WB); 1.39%], T2 [(fine + 8/15%WB); 1.49%], T3 [(fine + 10/17%WB); 1.41%] and T5 
[(coarse + 8/15%WB); 1.57%] but similar (p≥0.05) to birds on T6 [(coarse + 10/17%WB); 1.80%]. 
Birds on T1 (fine + 6/13%WB; 1.39%) had the lowest empty gizzard relative weight. In addition, 
a maize particle size effect (p≤0.0001) on the relative empty gizzard weight was observed. Birds 
on coarse diets (T2, T5 and T6) had heavier empty gizzards than birds on fine diets (T1, T3 and 
T4).  
4.7. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Caecal Short-Chain Fatty Acids Profile and Concentration (SCFAs) 
Amongst the three caecal SCFAs analysed, acetic acid (approximately 8147.14 µg/g) was 
predominant in the caecal contents of all birds. This was followed by butyric (approximately 
128.96 µg/g) and propionic acids (approximately 73.29 µg/g). 
 
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Table 4. 6: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle size on 
relative organ weights 
    %1 
Trt2 %Wheat PS5 Empty Full Full  Empty Full  Empty Heart Liver 
bran Crop provent gizzard gizzard intest7 intest8 
S3 F4 6 
T1  6 13 Fine 0.38 0.49 2.75 1.39c 5.17 3.09 0.48 1.79 
T2 8 15 Fine 0.45 0.40 2.58 1.49bc 5.32 2.98 0.47 1.72 
T3 10 17 Fine 0.42 0.51 2.87 1.41bc 5.05 2.89 0.43 1.68 
T4 6 13 Coarse 0.43 0.49 3.31 2.00a 5.46 3.71 0.54 1.82 
T5 8 15 Coarse 0.43 0.36 2.82 1.57bc 4.81 2.98 0.44 1.65 
T6 10 17 Coarse 0.45 0.47 2.98 1.80ab 4.84 2.86 0.49 1.95 
Pooled SEM9  0.06 0.11 0.20 0.09 0.46 0.29 0.04 0.19 
  Main effect 
%Wheat bran          
 S F           
 6 13  0.41 0.49 3.03 1.69 5.32 3.40 0.51 1.80 
 8 15  0.44 0.38 2.70 1.53 5.06 2.98 0.46 1.69 
 10 17  0.44 0.60 2.93 1.61 4.95 2.87 0.46 1.82 
SEM 0.04 0.08 0.14 0.06 0.33 0.20 0.03 0.14 
M aize  particle size          
 Fine 0.42 0.54 2.73 1.43b   5.18 2.98 0.46 1.73 
  Coarse 0.43 0.44 3.03 1.79
a 5.04 3.18 0.49 1.81 
SEM 0.04 0.07 0.12 0.52 0.27 0.17 0.03 0.11 
Source of variation  P-value 
Wheat bran * Maize particle 0.88 0.44 0.53 0.02 0.69 0.45 0.45 0.67 
size  
Wheat bran   0.84 0.17 0.26 0.21 0.72 0.18 0.46 0.76 
Particle size  0.78 0.26 0.08 ≤.0001 0.71 0.40 0.43 0.63 
%1: Absolute weights expressed as percentage of live weight; Trt2: Treatment; S3: Starter phase; F4: 
Finisher phase; PS5: Maize particle size; Full provent6: Full proventriculus; Full intest7: Full intestines; 
Empty intest8: Empty intestines; SEM9: Standard error of the means 
 
Also, for each SCFAs, there was no interaction between WB level and maize particle size. Figures 
4.6, 4.7 and 4.8 show the observed trend in the concentration of acetic, propionic and butyric acids 
across treatments. 
Again, amongst treatments, there was no linear increase (p≥0.05) in concentration of any of the 
analysed caecal SCFAs in response to the increasing level of WB as shown in Table 4.5. There 
were some numerical increases in the concentration of acetic, propionic and butyric acid of birds 
fed coarse diets (T4, T5 and T6) (Table 4.7).  
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12000
10000
8000
T1: Fine + 6/13%WB 
T2: Fine + 8/15%WB 
6000
T3: Fine + 10/17%WB 
4000 T4: Coarse + 6/13%WB 
T5: Coarse + 8/15%WB 
2000
T6: Coarse + 10/17%WB 
0
T1 T2 T3 T4 T5 T6
Treatment
Figure 4. 5: Acetic acid concentration in caecal content 
 
140
120
T1: Fine + 6/13%WB
100
T2: Fine + 8/15%WB
80
T3: Fine + 10/17%WB
60 T4: Coarse + 6/13%WB
40 T5: Coarse + 8/15%WB
T6: Coarse + 10/17%WB
20
0
T1 T2 T3 T4 T5 T6
Treatment
Figure 4. 4: Propionic acid concentration in caecal content 
 
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Concentration, µg/g 
Concentration, µg/g, 
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200
180
160
T1: Fine + 6/13%WB
140
T2: Fine + 8/15%WB
120
100 T3: Fine + 10/17%WB
80 T4: Coarse + 6/13%WB
60 T5: Coarse + 8/15%WB
40 T6: Coarse + 10/17%WB
20
0
T1 T2 T3 T4 T5 T6
Treatment
Figure 4. 6: Butyric acid concentration in caecal content 
 
Table 4. 7: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle 
size on caecal short-chain fatty acids concentration 
                                                  µg/g 
Main effect Acetic acid Propionic acid Butyric acid 
%Wheat bran    
Starter Finisher    
6 13 9510.72 87.39 144.65 
8 15 6606.17 53.23 86.71 
10 17 8324.29 53.23 155.53 
SEM1 1 216.47  24.73  19.60 
Maize particle size 
 Fine 7872.48 68.43 116.22 
 Coarse 8421.63 78.14 141.71 
SEM 933.24 20.56 16.00 
Source of variation                                        P-value 
Wheat bran 0.26 0.26 0.63 
Maize particle size 0.70 0.70 0.75 
SEM1: Standard error of means    
 
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Concentration, µg/g 
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4.8. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Caecal pH and Microbial Count 
Figure 4.9 shows caecal pH values obtained from the interaction between WB level and maize 
particle size across treatments. There was no significant WB-effect (p=0.63) or maize particle size 
effect (p=0.82) on caecal pH (Table 4.8).  
6
5.84
5.9
5.8
5.69 T1: Fine + 6/13%WB
5.7 5.61
5.58 T2: Fine + 8/15%WB
5.53
5.6
T3: Fine + 10/17%WB
5.47
5.5
T4: Coarse + 6/13%WB
5.4 T5: Coarse + 8/15%WB
5.3 T6: Coarse + 10/17%WB
5.2
5.1
T1 T2 T3 T4 T5 T6
Treatment
Figure 4. 7: Caecal pH values 
  
Also, analysis of the caecal content showed a relative abundance of Lactobacillus spp. (average 
of 9.40 log10 cfu/ml) as compared to E. coli (average of 6.78 log10 cfu/ml) across treatment. 
No significant interactive effect (p=0.15) was identified as shown in Figure 4.10. In addition, there 
was no linear response in the count of E. coli and Lactobacillus spp. as the level of WB increased 
neither was the effect of maize particle size significant (p≥0.05) (Table 4.9). 
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pH
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14
12
10
T1 (Fine + 6/13%WB)
8 T2 (Fine + 8/15%WB)
6 T3 (Fine + 10/17%WB)
T4 (Coarse + 6/13%WB)
4
T5 (Coarse + 8/15%WB)
2
T6 (Coarse + 10/17%WB)
0
E. coli Lactobacillus spp.
Figure 4. 8: Interactive effect of dietary fibre level (using wheat Bran as a DF source) and maize particle size 
on caecal microbial count 
 
Table 4. 8: Effect of dietary fibre level (using wheat Bran as a DF source) and maize 
particle size on caecal pH and microbial population 
  log10 cfu/ml 
Main effect pH Escherichia coli  Lactobacillus spp. 
%Wheat bran 
Starter Finisher    
6 13 5.65 6.99 9.47 
8 15 5.63 7.19 9.35 
10 17 5.57 6.16 9.37 
SEM1   0 .45 0 .42 
Maize particle size 
Fine 5.59 6.89 9.07 
Coarse 5.65 6.66 9.72 
SEM 0.08 0.36 0.34 
Source of variation                         P-value 
%Wheat bran 0.63 0.25 0.98 
Maize particle size 0.82 0.66 0.19 
SEM1: Standard error of means    
 
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Colonies of microbes present, log10 cfu/ml  
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4.9. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Intestinal Morphometric Measurements 
Table 4.9 shows the effect of dietary treatments on morphological structures in the jejunum and 
ileum. Results obtained showed no significant effect of WB level and maize particle size on the 
villi height (VH), crypt depth (CD) and villi height: crypt depth (VH: CD) ratio in the jejunum and 
ileum.  
  
Table 4. 9: Effect of dietary fibre level (using wheat Bran as a DF source)  and maize particle size on 
morphology of the jejunum and ileum 
Parameter   Jejunum Ileum 
Treatment % Wheat bran Maize Villi Crypt VH:CD1 Villi Crypt VH:CD 
Starter Finisher particle height depth height depth 
size (μm) (μm) (μm) (μm) 
T1 6 13 Fine 801.25 156.39 5.58 726.42 297.56 4.68 
T2 8 15 Fine 669.57 132.13 5.18 596.66 141.39 4.24 
T3 10 17 Fine 625.73 157.25 4.51 587.37 146.56 4.46 
T4 6 13 Coarse 656.55 118.97 5.54 592.28 112.26 5.31 
T5 8 15 Coarse 740.56 144.59 5.29 671.75 121.38 5.62 
T6 10 17 Coarse 630.73 127.60 4.94 638.02 118.58 5.44 
Pooled SEM2   59.62 20.87 0.58 53.04 67.65 0.63 
                                                      Main effect 
%Wheat bran        
 Starter Finisher        
 6  13   728.90 137.68 5.56 659.36 204.91 5.00 
 8 15   705.06 138.36 5.23 634.21 132.57 4.93 
 1 0 17   628.23 142.43 4.73 612.70 131.38 4.95 
SEM    42.16 14.76 0.41 37.51 47.84 0.44 
Maize particle size         
    Fine 698.85 148.59 5.09 636.82 195.17 4.46 
    Coarse 675.95 130.39 5.26 634.02 117.40 5.46 
SEM     34.42 12.05 0.34 30.62 39.06 0.36 
Source of variation                                           P-Value 
Wheat bran * Maize particle size 0.20 0.45 0.92 0.12 0.40 0.83 
Wheat bran   0.23 0.97 0.37 0.68 0.47 0.99 
Maize particle size   0.64 0.30 0.72 0.95 0.17 0.06 
VH:CD1: Villi height to crypt depth ratio; SEM2: Standard error of the mean 
 
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In the jejunum, the VH, CD and VH: CD averaged 687.40μm, 139.49μm and 5.17. On an average, 
the ileal measurements for VH, CD and VH: CD were 635.42μm, 156.29μm and 4.69. 
Histopathogical images of the jejunal and ileal segments of birds on dietary treatments are shown 
in Plates 1 and 2 respectively. 
 
T1 T2 T3
 
  
 
 
 
 
 
 
T4 T5 T6
6
 
Plate 4. 1: Histopathogical images of the jejunal segments of birds on dietary treatments 
 
 
 
 
 
 
 
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T1 T2 T3 
T4 T5 T6 
Plate 4. 3: Histopathogical images of the ileal segments of birds on dietary treatments 
 
4.10. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle 
Size on Blood Haematological Indices and Serum Glucose 
Table 4.10 shows the effect of the dietary treatments on red blood cells (RBC), haematocrit (Hct), 
haemoglobin (HGB), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) 
and mean corpuscular haemoglobin concentration (MCHC) across treatments. The effect of WB 
level and maize particle size on RBC, HGB, Hct, MCV, MCH and MCHC count across treatments 
was comparable (p≥0.05). Maize particle size significantly (p≤0.05) influenced glucose levels in 
the blood with birds fed coarse maize particles (9.72mmol) having a lower serum glucose content 
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as compared to birds fed fine maize particles (11.29mmol) (Table 4.11). However, no response 
(p=0.22) to increasing level of WB was observed. 
Table 4. 10: : Effect of dietary fibre level (using wheat Bran as a DF source)  and maize particle size on 
blood haematology and glucose levels 
Trt1 %WB2 PS3 RBC4 HGB5 Hct6  MCV7 MCH8 MCHC9 Glucose 
12
Starter Finisher (10 /L) (g/dL) (%) (fL) (pg) (g/dL) (mmol) 
T1 6 13 Fine 2.95 12.80 34.48 111.90 43.43 38.75 11.34 
T2 8 15 Fine 3.03 13.48 27.82 114.42 44.68 39.00 12.04 
T3 10 17 Fine 2.99 10.60 32.90 115.85 43.75 37.75 10.50 
T4 6 13 Coarse 2.86 12.60 34.55 116.87 44.00 37.67 9.82 
T5 8 15 Coarse 2.91 12.92 33.40 116.46 44.34 38.40 10.02 
T6 10 17 Coarse 2.97 12.98 35.02 118.10 43.64 36.60 9.32 
Pooled SEM10   0.34 3.05 4.22 0.34 0.98 1.96 0.63 
                                                                       Main effects 
%Wheat bran         
 Starter Finisher         
 6  13  2.91 12.70 33.15 114.38 43.71 32.21 10.58 
 8 15  2.97 13.20 31.15 115.44 44.51 38.70 11.03 
 10 17  2.98 11.79 34.79 116.98 43.70 37.18 9.91 
SEM   0.11 0.70 2.16 1.39 0.79 0.40 0.45 
Maize particle size         
    Fine 2.99 12.29 33.98 114.06 43.95 38.50 11.29a 
    Coarse 2.91 12.83 32.08 117.14 43.99 37.56 9.72b 
SEM   0.09 0.61 1.90 1.22 0.70 0.36 0.36 
Source of variation  P-value 
Wheat bran * Maize particle size 0.58 0.55 0.50 0.77 0.93 0.88 0.80 
Wheat bran   0.90 0.39 0.52 0.51 0.73 0.06 0.22 
Maize particle size   0.94 0.33 0.45 0.09 0.97 0.08 0.01 
Trt1: Treatment; WB2: Wheat bran; PS3: Particle size; RBC4: Red blood cell; HGB5: Haemoglobin; Hc6: 
Haematocrit; MCV7: Mean corpuscular volume; MCH8: Mean Cell Haemoglobin; MCHC9: Mean Cell 
Haemoglobin Concentration; SEM10: Standard error of the means 
Means in a column with different superscripts are significantly different at P ≤ 0.05 
 
4.11. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle 
Size on Immune Status 
Results obtained for differential white blood cell count showed a relative abundance of heterophils 
(52.53%), lymphocytes (33.83%), eosinophils (9.58%), monocytes (3.93%) and basophils  
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Table 4. 11: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle size on 
white blood cell differentials and immune relative organ weight (expressed as a percentage of live weight)  
T 1  rt   % 
%Wheat bran PS2 Bas3 Eosi4 Mono5 Hetero6 Lymp7 H:L8 Thymus Spleen 
Starter Finisher 
T1 6 13 F9 0.00 12.00 2.75 45.00 40.25 1.33 0.21 0.10 
T2 8 15 F 0.40 7.60 4.20 58.00 29.80 2.02 0.20 0.11 
T3 10 17 F 0.00 8.20 3.40 55.60 32.60 1.84 0.17 0.18 
T4 6 13 C10 0.00 10.33 4.00 47.67 38.00 1.51 0.50 0.35 
T5 8 15 C 0.17 9.17 4.83 55.33 30.50 1.98 0.14 0.17 
T6 10 17 C 0.20 10.20 4.40 53.60 31.80 1.81 0.23 0.14 
Pooled SEM11  0.15 0.95 0.95 5.06 5.06 1.69 0.12 0.10 
Main effect 
%Wheat bran          
 Starter Finisher          
 6 13   0.00 11.17 3.38 46.33 39.13 1.42 0.36 0.23 
 8 15   0.28 9.20 4.52 56.67 30.15 2.00 0.17 0.14 
 10 17   0.10 8.38 3.90 54.60 32.20 1.83 0.20 0.16 
SEM    0.11 1.14 0.64 3.42 2.86 0.23 0.09 0.07 
Maize particle size          
    F 0.20 3.45 9.27 52.87 34.22 1.73 0.19 0.13 
    C 0.06 4.41 9.90 52.20 33.43 1.77 0.29 0.22 
SEM   0.10 0.57 1.02 3.04 2.53 0.21 0.07 0.06 
Source of variation                           P-value 
WB * PS   0.79 0.95 0.59 0.88 0.95 0.96 0.38 0.35 
Wheat bran   0.26 0.54 0.33 0.18 0.16 0.32 0.28 0.70 
Particle size   0.31 0.25 0.67 0.88 0.83 0.90 0.35 0.29 
Trt1: Treatment; PS2: Maize particle size; Bas3: Basophils; Eosi4: Eosinophils; Mono5: Monocytes; Hetero6: 
Heterophils; Lymp7: Lymphocytes; H:L8: Heterophils to lymphocytes ratio: F9: Fine; C10: Coarse; SEM11: 
Standard error of means  
 
(0.13%), in descending order (Table 4.11).  The values obtained for eosinophils, monocytes, 
heterophils, lymphocytes and heterophils: lymphocytes ratio for all birds were not significantly 
affected (p≥0.05) by WB level or maize particle size or an interaction between them. Similarly, no 
interactive effect or WB-effect was observed on the immune organs. 
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4.12. Economics of Production 
The cost of feed per kilogram for diets for both starter and finisher phase are shown in Table 
4.13. There was a linear increase in cost of feed per kilogram as the wheat bran inclusion level 
increased. 
The effect of dietary treatments on selected cost variables is shown in Table 4.14. It cost Ghȼ 0.40 
and Ghȼ 0.24 lesser to produce a kilogram of the final body weight (FBW) and dressed weight 
(DW) respectively of birds on T3 as compared to birds on the control diet. Also, the cost/kg weight 
gain, total feed cost/kg of final body weight and total feed cost /kg of dressed weight reduced as 
WB level increased. 
Table 4. 12: Cost of feed per kilogram of dietary treatments (GHȼ) 
Treatment %Wheat bran Maize Cost/kg of feed 
particle 
Starter Finisher  Starter Finisher size
T1 6 13 Fine 1.95 2.12 
T2 8 15 Fine 1.98 2.15 
T3 10 17 Fine 2.01 2.18 
T4 6 13 Coarse 1.95 2.12 
T5 8 15 Coarse 1.98 2.15 
T6 10 17 Coarse 2.01 2.18 
 
Table 4. 13: Effect of dietary fibre level (using wheat Bran as a DF source) and maize particle size on 
feed cost variables (GHȼ) 
Treatment %Wheat bran Maize Cost/kg of feed Overall cost Cost/kg Total feed cost/ 
particle consumed/bird of feed weight kg 
Starter Finisher Size day 1 to day 22 to consumed gain FBW1 DW2 
day 21 day 42 /bird 
T1 6 13 Fine 3.92 5.10 9.01 3.90 2.94 3.84 
T2 8 15 Fine 3.60 5.12 8.72 3.63 2.88 3.73 
T3 10 17 Fine 3.47 4.37 7.85 3.44 2.48 3.49 
T4 6 13 Coarse 3.53 5.24 8.77 3.52 3.06 3.94 
T5 8 15 Coarse 3.79 4.96 8.75 3.70 3.05 3.93 
T6 10 17 Coarse 3.92 5.48 9.40 3.71 2.98 3.86 
FBW1; DW2; Dressed weight 
 
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CHAPTER FIVE 
DISCUSSION 
5.1. Percentage mortality 
Dietary or environmental factors can lead to the incidence of infections and diseases in broilers 
(Martínez et al., 2015). This weakens the immune system leading to a possible occurrence of 
morbidity or mortality. In this trial, the 17 mortalities recorded were well spread across treatments 
and amounted to an overall mortality rate of 5.67%. Post mortem autopsies carried out did not 
indicate feed components as the cause of death. Also, hygienic practices such as the provision of 
clean water and feed, maintenance of a good environment is critical in order to promote healthy 
development during broiler production. All these were duly observed throughout the trial. Stress 
that arises form growth and environmental adaptation could be a contributing factor to the 
observed results. In addition, breeders such as Hy-line and Dekalb have indicated an acceptable  
weekly morality rate of 0.8-1.5% in broiler production (Hy-Line, 2009; Lohmman, 2009; Dekalb, 
2009). Based on this, the estimated maximum mortality rate for six weeks is 6.9%. By day 42, 
5.67% mortality rate was recorded. This shows that increasing WB levels with fine or coarse maize 
particles did not adversely affect the health status of growing broilers. The findings in this study 
is similar to that of Idan (2019) and Martínez et al. (2015) who fed up to 12% and 200g/kg WB 
respectively to poultry. In their work, mortality rate was no attributed to dietary effects. 
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5.2. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Apparent Nutrient Digestibility 
Determining the bioavailability of nutrients in feed ingredients is necessary in order to optimize 
feed efficiency and reduce feed cost (Ravindran, 2013). A decrease in nutrient digestibility in 
monogastric (broiler) diets has been linked to dietary fibre levels (Wilfart et al, 2007; Urriola et 
al., 2009). As an anti-nutritional factor, dietary fibre is able to encapsulate dietary nutrients through 
the formation of complexes, which hinders nutrient digestion and absorption (Bindelle et al., 2008; 
Mateos et al., 2012). In this study, increasing the levels of dietary fibre during the finisher phase 
increased the crude fibre content in experimental diets (Table 3.3 and Table 3.4). However, the 
increased dietary fibre levels did not adversely affect digestibility coefficients of DM, OM and CP. 
This may be attributed to the effect of fibre type, level of inclusion and maize particle sizes used 
in this study. Contrary to the traditional view about dietary fibre, inclusion of dietary fibre 
especially insoluble fibre (such as in WB) in broiler diets increases gizzard activity as fibre is hard 
to grind (Mateos et al., 2012). This may have resulted in an enhanced GIT motility, an increase in 
the secretion of digestive enzymes in the pyloric region, HCL production and microbial 
fermentation, which lower gut pH (Zaefarian et al., 2016; Kheravii et al., 2018). All these 
beneficial effects may have accounted for the observed similarities in the digestibility coefficients. 
In addition, when gut pH is low, pepsin stimulation and mineral digestibility are enhanced which 
may have accounted for the observed similarities in CP and OM digestibility coefficients. 
Adibmoradi et al. (2016) accounted improvements in nutrient digestibility when birds were fed 
rice hulls (insoluble fibre) at an inclusion rate of 1.5% as compared to 0.75% to an increase in 
secretion of HCL as DF levels increased. Similar to the results of this study, González-Alvarado 
et al. (2010) reported an improvement in the digestibility coefficients of dry matter, organic matter 
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and soluble ash when oat hulls (30g/kg) were included in broilers diets as compared to sugar beet 
pulp (30g/kg). In contrast, Khempaka et al. (2009) observed a reduction in dry matter and organic 
matter digestibility as the inclusion level of dried cassava pulp increased from 8 to 16% in broiler 
diets. In this trial, including WB up to 17% did not serve as an anti-nutritional factor, rather, the 
presence of WB in the GIT created a favourable environment for digestive enzymatic activities.   
5.3. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Overall Growth Performance (day one to day 42) 
The type of fibre and level of inclusion can reduce or promote feed intake in broilers (Mateos et 
al., 2012). An increase in fibre content may result in the dilution of dietary energy (Classen, 2017). 
This leads to an increase in feed intake by broilers in order to meet their daily nutrient and energy 
needs (Nahashon et al., 2006). In this study, all experimental diets were formulated to be isocaloric 
and isonitrogenous as WB was not a feed additive. As such, the observed significant WB level 
effect on ADFI by day 42 can be attributed to the influence of the insoluble nature of the fibre type 
in WB on digesta passage rate as well as an increase in the physical capacity of the birds’ GIT. 
Wheat bran is characterized by a faster digesta passage rate, which normally results in early gastric 
emptying, which may lead to a higher feed intake (Montagne et al. 2003; Hetland et al. 2004) as 
observed in this study. Also, birds naturally eat to ‘gut fill’ with a positive correlation exiting 
between feed intake and the physical capacity of a bird’s GIT (Nir et al., 1994a; Ferket and Gernat, 
2006). In this study, the WB effect on ADFI was highest in birds on diets with the highest WB 
inclusion level; 10 and 17%WB at starter and finisher phases respectively. This implies that the 
presence of structural components such as high levels of WB at both starter and finisher phases 
caused a progressive increase in the physical capacity of the GIT of birds; thus, enabling an 
increase in feed intake. The trend in the interactive effect on ADFI can be attributed to the trend 
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in WB effect observed in this study. In contrast to the findings of this trial, Donkoh et al., (1999) 
observed a linear reduction in ADFI as WB level (150g, 250g, 350g and 450g) increased in a 
broiler trial (21-56 days). However, result obtained by Adibmoradi et al. (2016) when insoluble 
fibre was fed to broilers is in agreement with the findings of this study.  
As birds grow, their gape develops and mature enabling them to consume the preferred larger feed 
particles (Amerah et al., 2007a). As such, feed intake of birds on diets with moderate or large feed 
particles is expected to increase as they grow. The lack of maize particle size effect at the various 
WB levels suggests that although the GIT of birds fed coarse maize particles become progressively 
adapted to the nature of their diet, the rate of feed intake was not high enough to elicit a significant 
difference in ADFI. Results obtained corroborates that of Rubio et al. (2020) who reported no 
maize particle size effect on day 42 when maize particles of sizes: 615, 863, 1644 and 2613μm 
were fed to broilers. Furthermore, Oppong-Sekyere et al. (2012) reported similarities in feed intake 
when broilers were fed fine (713.82µm) and coarse (1462µm) maize particles.  
Weight gain in broilers is a function of the dietary protein content (Beski et al., 2015). Wheat bran 
has a good amount of nutrients such as protein, amino acids, and a good source of B vitamins, 
which maximizes growth (Prueckler et al., 2014). On the other hand, WB is mainly made up of 
arabinoxylans and a lesser fraction of beta-glucans and cellulose (Chalamacharla et al., 2018). 
These components can negatively influence the bioavailability of dietary nutrients to birds, hence 
impairing nutrient digestion, utilization and weight gain (Woyengo et al., 2008). Results obtained 
on ADG by day 42 indicates that increasing the level of WB in this study did not affect the 
bioavailability of nutrients needed for growth. Also, this assertion is evidenced by the observed 
similarities in nutrient digestibility coefficients (Table 4.1). The fermentation of DF is known to 
produce SCFAs, which serves as energy for villi and crypt cells responsible for nutrient digestion 
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and absorption (Taheri et al., 2016). This may also have accounted for the improved ADG at day 
42. These results are contrary to the findings of Sanchez et al. (2019) who observed a decrease in 
weight gain when birds were fed insoluble fibre (11% rice bran). However, the findings of Hetland 
and Svihus (2001) agrees with that of this trial. In their trial, insoluble fibre (oat hulls) had no 
negative effect on weight gain of broilers and this was attributed to the increase in gut physical 
capacity of the birds.  
Feed conversion ratio is a measure of how much feed consumed is efficiently converted into body 
tissues (Kantanka, 2013). The inclusion of dietary fibre and medium to large feed particles in 
broiler diets is said to enhance grinding action and musculature development of the gizzard 
(Svihus, 2011). A well-developed gizzard enhances feed utilisation due to the associated 
improvements in digestive processes such as increase in retention time, HCL secretion, digesta 
reflux and microbial fermentation (Hetland et al., 2003; Sacranie et al., 2012). The improved FCR 
of birds fed coarse maize particles by day 42 (Table 4.2) can be attributed to the functional and 
well-developed nature of their gizzards. In addition, less energy is needed for feeding and grinding 
when the gizzard is adequately developed (Amerah et al., 2007a). This makes more energy 
available for growth and development as observed in birds fed coarse maize particles. Naderinejad 
et al. (2016) and (Kheravii et al., 2017a; Kheravii et al., 2017b) observed improvements in FCR 
when maize particle size was increased in broilers which agrees with the findings of this trial. In 
addition, supplementing broilers diets with 50% fine and coarse particles each improved FCR and 
ADG as compared to feeding fine particles alone (Xu et al., 2015b). The maize particle size effect 
on FCR positively influenced the observed significant interaction by day 42 (Table 4.2). 
 
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5.4. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Growth Performance during the Starter Phase (day one to day 21) 
Voluntary feed intake in broiler chicks can be influenced by age, dietary particle size and fibre 
level in diets (Amerah et al., 2007b; Zaefarian et al., 2016). Broiler chicks may have difficulties 
in swallowing and grinding diets with high fibre levels and larger feed particle sizes (Ravindran 
et al. 2006). This can be attributed to their smaller gape dimensions and the undeveloped nature 
of the gizzard’s myelinated muscles and koilin layer (Kiarie and Mills, 2019). However, the 
similarities in ADFI from day 1 to day 21 suggests that the two maize particle sizes did not 
impair swallowing and subsequent feed intake. Furthermore, the results indicate an adaptation of 
the gizzard of chicks on coarse maize particles and highest WB level to the dietary components. 
This may have enhanced quick and effective grinding which in turn prevented excessive or 
reduced feed intake. This confirms the assertion made by Mateos et al. (2012) that 
supplementing broiler diets with moderate amounts of dietary fibre and coarse feed particles 
prevents feed wastage and increases productivity. The results obtained corroborates that of 
González-Alvarado et al. (2007) who observed no effect on ADFI when 3% oat hulls were 
included in broiler diets from day 1 to day 21. 
The negative effect of dietary fibre inclusion on voluntary feed intake in broiler chicks is said to 
result in a proportional reduction in ADG and FCR especially from day 0 to day 21 (Pacheco et 
al., 2018). However, the improved ADG from day 0 to day 21 can be attributed to the beneficial 
effect coarse maize particles and moderate amounts of WB had on the development of digestive 
organs and processes, which enhance early weight gain. This explains the higher weight gain 
observed in birds fed 6%WB with coarse maize particles.  
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Reports from studies indicate a better FCR for broilers fed coarse maize particles (Amerah et al., 
2007b; Nir et al., 1995) or brans (Taheri et al., 2016). Results from this study confirms the assertion 
that dietary manipulation of feed particle size can be a potential nutritive strategy used to mitigate 
the negative effects dietary fibre may have on broiler growth (Amerah et al., 2007a; Amerah et 
al., 2007b; Kheravii et al., 2018). In contrast, Pacheco et al. (2018) indicated a reduction in ADG 
when birds were fed maize particles larger than 1000μm as energy for growth is diverted into 
the grinding of coarser maize particles. The improved FCR of birds on T4 shows that ADFI 
from day 1 to day 21 was efficiently translated in ADG. Also, the observed results could be due to 
a reduction in the viscosity of the digesta liquid phase which enabled efficient nutrient digestion 
and utilization (Yasar, 2003). The inclusion of brans and coarse particles in diets makes the digesta 
spongy, which increases the permeability of the digesta to digestive enzymes due to the available 
spaces between the digesta particles (Lentle, 2005; Sarikhan et al., 2010). These results corroborate 
that of Taheri et al. (2016) who observed an improvement in FCR when broiler diets were 
supplemented with 4 and 8%WB. Wheat bran is known for its bulk effect on the GIT hence feeding 
high amounts may cause laxative effects in broilers (Hyatt et al., 2012). The improved BW by day 
21 demonstrates that increasing WB level with fine or coarse maize particle sizes did not promote 
residues of unhealthy compounds in the gut to impair growth and development in experimental 
birds by day 42. Khempaka et al. (2009), observed a linear decrease in the body weight of broilers 
as the inclusion rate of insoluble fibre (dried cassava pulp) increased from 8 to 16%. 
5.5. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Growth Performance during the Finisher Phase (day 22 to day 42) 
In order to maximize broiler growth performance and productivity, the composition of diets must 
be adjusted as broilers age. From day 22 to day 42, maize particle sizes were kept constant with 
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WB level increasing from 6, 8 and 10% to 13, 15 and 17%.  The crude fibre content in broiler diets 
as they grow is critical to their optimal development (Mateos et al., 2012). The lack of adverse 
effect of the increased crude fibre content (Table 4.4) with fine or coarse maize particles on ADFI, 
ADG and FCR from day 22 to 42 can be attributed to a balance in digesta passage rate. Wheat 
bran is known for a faster digesta passage and an increase in WB level is expected to cause an 
increase in digesta mass and passage in the gut (Taheri et al., 2016). An increase in digesta mass 
may also lead to the occurrence of abrasive effects on intestinal walls leading to a reduction in 
nutrient digestion and absorption (Montagne et al., 2003). Current results show that the increase 
in WB level (dietary fibre) did not impair digestive processes and nutrient utilization. 
5.6. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Carcass Parameters 
Optimal development of carcass traits especially prime cuts (such as thighs, breasts and back of 
broilers) is important, as they are indicators of the economic value of broilers (Nkukwana et al., 
2014). The level of dietary protein accretion in broilers directly influences the development of 
prime cuts (Beski et al., 2015). However, high levels of fibre in broiler diets potentially reduces 
the development of carcass traits (Bindelle et al., 2008). This is because of the linear decrease in 
the digestibility and absorption of nutrients essential for the development of muscles and tissues 
(Oloruntola et al., 2016). Despite the significant differences observed in ADFI by the day 42 (Table 
4.2), crude protein, organic matter and dry matter digestibility (Table 4.1) were not impaired. This 
may explain the similarities in final body weights by day 42 and subsequent similarities in carcass 
traits. Furthermore, since the experimental diets were formulated to be isocaloric and 
isonitrogenous, the similarities in protein levels and energy levels may have influenced the 
similarities in carcass traits. Contrary to the findings of this trial, Shirzadegan and Taheri (2017) 
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observed an improvement in the relative weights of the breast, drumsticks, thigh, abdominal fat, 
heart and liver when alfafa meal or rice bran were included in broiler diets (up to 6%). 
The quality of broiler mash diets can be evaluated by the effect of dietary particle size on carcass 
traits (Aguzey et al., 2018). Birds fed medium to large maize particles tend to consume a more 
balanced nutrient profile due to the lack of particle size preference (Parsons et al., 2006). The lack 
of any adverse effect of maize particle size on carcass parameters suggests that the maize particle 
sizes used in this trial encouraged the consumption of a more balanced nutrient profile. The 
similarities in the effect of maize particles on carcass parameters is consistent with results of 
Ribeiro et al. (2002) (337 to 936μm maize particles) and Benedetti et al. (2011) (460 to 870μm 
maize particles). On the other hand, Parsons et al. (2006) noted a linear reduction in breast weight 
as maize particle sizes (781, 950, 1,042, 1,109, and 2,242μm) increased.  They explained this to 
be due to the diversion of digestible energy from breast growth to gizzard growth and development. 
 5.7. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Relative Organ Weights 
The gizzard responds to changes in dietary composition by structural adaptation (Kheravii et al., 
2018). The presence of structural components such coarse particles and dietary fibre in the gizzard 
might have led to increase in the contraction rate of the myelinated muscles and koilin layer of the 
gizzard in order to accommodate the extra grinding resulting from the digesta texture (Parsons et 
al., 2006; Svihus, 2011). The higher relative weight of birds fed coarse maize particles can be 
attributed to the progressive increase in gizzard musculature of these birds to be able to break down 
ingested feed. This might have resulted in the increased relative weight of the empty gizzards, 
which is essential for an efficient nutrient digestibility (Kheravii et al., 2018). Similar to the results 
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of this study, Jacobs et al. (2010) and Xu et al. (2015b) observed an increase in gizzard weights 
when maize particle size increased in broiler diets. In addition, Nir and Pitchi (2001) reported a 
positive correlation between relative gizzard weights and feed particle size in mash diets as 
observed in the trial. The observed significant interactive effect on the relative empty gizzard 
weights can be explained by the influence of maize particle size. Findings of this trial are similar 
to those of Xu et al. (2015c) where gizzard weights increased linearly as maize particle sizes 
moved from 422 to 431, 471, 509, 542, and 640μm. 
An increase in the musculature of digestive organs such as the crop, proventriculus and intestines 
is also a physiological response to the extended period of time a mass of ingested feed has to stay 
in these sections of the GIT (Rodríguez et al., 2006; Savon et al., 2006). Despite the significant 
differences (p≤0.05) in fibre intake by day 42, the absence of the aforementioned phenomenon 
demonstrates feed intake of the various treatments was not high enough to effect a marked increase 
in the relative empty weights of these organs. By contrast, Mazhari et al. (2015) recorded higher 
relative intestinal weights in broilers fed 600g/kg wheat screenings as compared to those fed 150, 
300 and 450g/kg. Current results are however similar to those of  this study, Khempaka et al. 
(2009) observed no differences in organ weights when up to 16% insoluble fibre (cassava pulp) 
was fed to broilers. Weights organs such as pancreas, liver and kidney are indices of toxicity in 
broilers (Obun et al., 2011). Hence, an increase in their weights may indicate an increase in 
detoxification activities due to the presence of harmful compounds or anti-nutrients in the feed 
(Adesehinwa et al., 2011; Nortey et al., 2015). The observed similarities in relative liver weights 
is suggestive of absence or low levels of toxic particles in the experimental diets. Similar results 
were obtained by Aguilar et al. (2011). In contrast, López and Baião (2004) and Fronte et al. 
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(2013) linked feeding of coarse diets to an increase in liver weights of broilers which they 
attributed to the effect of feed particle spectra on the musculature of the liver.  
5.8. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on Caecal Short-Chain Fatty Acids (SCFAs) Profile, pH and Microbial Population 
The production rate and profile of SCFAs in the broiler gut is influenced by, the substrate available, 
age, breed and intestinal length (Walugembe, 2013). Arabinoxylan oligosaccharides produced 
from bactericidal degradation of WB are a very good source of butyric acid (Aoe et al., 2018).  
However, results obtained from this study showed a relative abundance of acetic (AA), butyric 
(BA) and propionic (PA) acid, in a decreasing order. This can be attributed to the effect of substrate 
(diet), microbial diversity and degree of disassociation on SCFAs. Wheat bran serves as a suitable 
substrate for the proliferation of a wide range of indigenous microbes due to its diverse NSPs 
composition (Deroover et al., 2017). Microbial degraders such as Bifidobacteria and Lactobacillus 
spp. can produce acetic and lactic acids respectively using WB as a substrate (De Maesschalck, 
2015). On the other hand, through cross feeding, butyrate-producing bacteria such as 
Faecalibacterium and Roseburia, can convert acetic and lactic acids to butyric acid (Moens et al., 
2016; Vermeulen et al., 2018). This suggests that the levels of SCFAs produced in this study might 
have been more dependent on the relative populations of microbes present in the caeca as 
suggested by Moens et al. (2016). Also, acetic acid (4.75) has a lower degree of disassociation 
(pKa) as compared to butyric (4.82) and propionic (4.88) acids (Hajati and Rezaei, 2010). The 
caecal pH values obtained in this trial ranged from 5.47 to 5.84 and this may have enhanced a 
faster disassociation of butyric and propionic acids. The trend in the concentrations of caecal 
SCFAs in this study is similar to that observed by Walugembe (2013) and Shang et al. (2020).  
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The pH along the GIT varies with the caecal pH of a matured broiler ranging from 5.8 to 6.8 
(Hajati, 2018). The caecal pH values obtained at the end of the trial ranged from 5.47 to 5.84 with 
no treatment effect. Moreover, the observed similarities in caecal pH can be attributed to the lack 
of differences in the effects of WB level and maize particle size on the concentrations of acetic, 
butyric and propionic acids in the caeca. Charbeneau and Roberson (2004), Singh et al. (2014) and 
Naderinejad et al. (2016) demonstrated a lack of particle size effect on gizzard pH when mash 
diets were fed to broilers compared to pelleted diets.  
Supplementation of broiler diets with insoluble dietary fibre has been suggested to be a readily 
available substrate for microbial fermentation (Jha et al., 2019). However, the extent in gut pH 
reduction resulting from fibre fermentation determines the microbial profile and count (Fuller, 
2001; Kheravii et al., 2018). According to Hajati (2018), the proliferation of Lactobacillus spp. 
increases at a pH range of 5.4 to 6.4 while E. coli survive at a pH range of 6 to 8. The lack of 
increase or decrease in the counts of Lactobacillus spp. and E. coli respectively as WB level 
increased suggests that, the microbial fermentation at the lowest level of WB inclusion was enough 
to cause a reduction in gut pH. This may have resulted in the creation of a favourable acidic 
environment for the early seeding of Lactobacillus spp. and reduction in the survival rate of E. 
coli. The observed trend in microbial population can also be attributed to effect of caecal SCFAs 
on gut microbial profile. Short chain fatty acids have the ability exert toxic effects on pathogenic 
bacteria through their antimicrobial properties but creates a suitable environment for the 
multiplication of beneficial bacteria (Kheravii et al., 2018).  
An increase in the level of fibre and feed particle size in broiler diets is proportional to an increase 
in microbial fermentation which results in a higher proliferation of beneficial bacteria, increased 
SCFAs concentration and reduction in gut pH (Kheravii et al., 2018). WB level and maize particle 
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size had no effect on the digesta after grinding in the gizzard in the current study. Hence, 
differences in digesta particle size which enhanced relative gizzard weights might have evened out 
between treatments by the time the digesta reached the caeca and may explain the similarities in 
caecal SCFAs concentrations, pH and microbial count. This agrees with reports of Hetland et al. 
(2002) and Hetland et al. (2004) who indicated a lack of influence of dietary particle size on the 
digesta after it leaves the gizzard. However, work done by Lentle (2005) contradicted this assertion 
stating the presence of coarser particles in broiler digesta after ingested feed passed through the 
gizzard. These differences in observations can be attributed to differences in feed uniformity and 
particle size ranges.  
5.9. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
on the Jejunal and Ileal Morphology 
The morphology of the villi and crypts in the small intestines are baseline indicators of feed 
efficiency and overall gut health (Wang and Peng, 2008; Xu et al., 2015a). The villi facilitate 
nutrient digestion and absorption through the luminal absorptive area (Silva et al., 2007; Biasato 
et al, 2018) while the crypt depth (CD) development is suggestive of intestinal maturation and 
crypt-cell turnover rate (Miles et al., 2006). The supplementation of broiler diets with insoluble 
fibre and large dietary particles enhances histopathological changes in the intestines through the 
production of SCFAs, which simulate the intestinal cells (Sarikhan et al., 2010). The similarities 
in the effect of WB level on villi height (VH) and villi to crypt depth ratio (VH: CD) implies that 
the digestive and absorptive function of the jejunum and ileum was maintained. Results obtained 
on CD of the jejunal and ileal segments is suggestive of a normal energy expenditure in villi 
synthesis across treatments. Physiologically, the changes in the morphology of the small intestines 
is a result of the progressive effort to adapt to dietary composition in order to improve feed intake 
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and nutrient absorption (Mourão et al., 2008). The lack of response in VH, CD and VH: CD as 
WB level increased implies that, the differences in WB levels were not high enough to trigger 
structural adaptations in order for nutrient digestion and absorption to be maintained. Feeding 
moderate or coarse particles of an insoluble fibrous diet increases digesta retention time (Kheravii 
et al., 2018). This leads to longer contact period between digesta and intestinal mucosa resulting 
in longer proliferative activity of the villi (Dahlke et al., 2003). In this study, the similarities in the 
relative weights of the full intestines is suggestive of similarities in digesta retention across 
treatments. The similarities in digesta retention time could have accounted for the similarities 
observed in the effect of maize particle size on VH, CD and VH: CD. These results are similar to 
reports of Amerah et al. (2007b) and Zang et al. (2009) which indicated the absence of maize 
particle size effect on gut morphology.  
5.10. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle Size 
Blood Haematological Indices and Serum Glucose  
The physiological and health condition of a bird is largely influenced by nutrition, drugs, 
pathological effects, environmental effects, age and breed (Gnonlonfin et al., 2012; Ekunseitan et 
al., 2013). Wheat bran (WB) is rich in antioxidants (flavonoids, phenolic acids, tocopherols, 
lignans, phytosterols and carotenoids), vitamin B complex and other bioactive compounds 
(Belobrajdic and Bird, 2013; Chalamacharla et al., 2018). Coupled with the positive effect it has 
on the development of a healthy gut, WB exerts a very good degree of antimicrobial and anti- 
inflammatory properties on the overall health of broilers. Nutrients such as protein, iron, copper, 
vitamin B2, B6, B12 and folic acid are essential in the normal production of RBC (Nyaulingo, 
2013). The RBC values obtained at the end of the trial fell within the normal physiological range 
of 1.93 to 3.5 1012/L (Jain, 1993). This implies that RBCs were effectively produced and utilized 
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for metabolic and chemical activities. A high haematocrit level indicates toxicity reduction and a 
better feed efficiency in broilers (Mitruka and Rawnsley, 1977; Onu and Aniebo, 2011). The 
haematocrit values of birds on the test diets were similar to that of birds on the control diet and fell 
within the normal haematocrit range for broilers [(22.0-35.0 %), (Jain, 1993)]. This implies that 
oxygen and carbon dioxide transport was carried out efficiently during processes such as nutrient 
digestion and utilization. The normal haematocrit levels are in sync with the improvement in FCR 
observed by day 42 (Table 4.2). This corroborates the findings of Donkoh et al. (2003) who 
reported no adverse effect on haematocrit when broiler diets were supplemented with insoluble 
fibre. The genetic makeup of broilers as well as environmental conditions may affect the MCV of 
birds (Onyishi et al., 2017). Similar to RBC and haematocrit values, MCV values of experimental 
birds were similar across treatments and did not deviate from the normal range. This is an 
indication that good management practices were observed throughout the trial. A deviation of 
HGB values from the normal range (7.0 – 13.0 g/dL) is suggestive of an anaemic condition and 
poor heart, liver or marrow function in broilers (Olagunju et al., 2013). The HGB value of birds 
on the control diet (13.48 g/dL) deviated slightly from the normal range for broilers however, it 
was similar to the HGB values of birds on the test diets. The observation in birds on the control 
diet is suggestive of a compensatory mechanism to increase the oxygen levels in the blood. 
However, none of the mortalities, which occurred in birds on the control diet was attributed to an 
anaemic or organ malfunction. The dietary energy available to a bird after digestion is measured 
by its serum glucose levels (Ofori, 2015). Serum glucose level in birds on fine diets was higher 
than that of birds on coarse diets. This may be attributed to the fact that birds on coarse diets may 
have used some of their energy in adjusting to the particulate nature of the feed during the early 
stages of their life.  
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5.11. Effect of Dietary fibre level (using wheat Bran as a DF source) and Maize Particle 
Size on Immune Status 
Basophils are responsible for histamine secretion (Vulevic et al., 2013) and are rarely found in the 
blood of chickens (Hidanah et al., 2018). However, basophil levels increase when there is stress 
due to high environmental temperature (Onyishi et al., 2017; Hidanah et al., 2018). This could 
have accounted for the presence of basophils in the blood of birds on T2, T5 and T6. Eosinophils 
are released in response to parasitic infections (Irizaary-Rovira, 2004) while elevated levels of 
heterophils reflect the occurrence of either a parasitic or bacterial infection (Mitchell and Johns, 
2008). The normal physiological range of eosinophils and heterophils percentages fort broilers is 
1.5 to 6.0% and 15.0 to 40.0% respectively (Jain, 1993). The absence of WB level or maize particle 
size effect indicates that the level of inclusion was not high enough to lower the elevated levels of 
eosinophils and heterophils. Lymphocytes produce antibodies to fight chronic antigenic 
stimulations (Hidanah et al., 2018) while monocytes serve as clearing agents in the blood which 
gets rid of dead cells or pathogenic microorganisms (Abbas et al., 2014; Bayona et al., 2017). The 
lymphocytes and monocytes values obtained in the study were lower than the normal minimal 
value of broilers [(45.0 to 70.00% and 5.0 to 10.0%); Jain, 1993]. However, no dietary effect was 
observed. 
According to Elmore (2006a and 2006b) the spleen and thymus are essential in accessing the 
response of the immune system to dietary components. As such, compensatory hypertrophy or 
cellular infiltration of the spleen and thymus by immune cells may occur as a response to infections 
or recovery in birds (Eshak et al., 2016). The similarities in the relative weights of the spleen and 
thymus of birds on the control diet and birds on the other test diets suggest that the test diets were 
nutritionally adequate to support and maintain the health of the birds. The antioxidant, anti-
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inflammatory and microbial growth-promoting effect of WB helps maintain gut health and 
immune status (Stevenson et al., 2012). Work done by Rodríguez et al. (2006) and González-
Alvarado et al. (2007) demonstrated the similarities in the relative weight of the spleen when 
different fibre sources were fed to layers and broilers respectively. 
5.12. Economic Evaluation 
Economic returns in broiler production can be improved through feed cost reduction, an optimal 
growth performance and flexibility in diet formulation (Costa et al. 2008). Feed cost is mostly 
reduced when AFIs partially or fully replace traditional feed ingredients in broiler diets (Onunkwo 
and George, 2015). The significant differences (P≤0.05) observed in the cost/kg/FC/bird (GHȼ) 
during the starter phase can be attributed to the observed trend in ADFI during the starter phase. 
This in turn may have influenced the trend of significance in the overall cost of FC consumed/bird 
(GHȼ). Even though there were significant differences in the cost per weight gain of birds, it did 
not translate onto the total FC/kg/FBW (GHȼ) and total FC/kg/DW (GHȼ). There was a linearly 
reduction as WB levels increased in total FC/kg/FBW (GHȼ) and total FC/kg/DW (GHȼ). It cost 
Ghȼ 0.40 and Ghȼ 0.24 lesser to produce a kilogram of the FBW and DW respectively of birds on 
T3 than those on the reference diet. The reduction in cost could be attributed to the relatively 
cheaper cost of wheat bran. Although the reduction seems small, it is important when large 
volumes of feed are being manufactured.  
  
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CHAPTER SIX 
CONCLUSIONS AND RECOMMENDATIONS 
6.1. Conclusions  
1. Broilers were able to efficiently digest and utilize diets containing up to 17%WB with fine 
(725μm) or coarse (1178μm) maize particles which is a good indicator broilers’ ability to 
physiologically adapt to the nature of their diets. 
2. Inclusion of up to 17%WB with fine (725μm) or coarse (1178μm) maize particles in broiler 
diets increased overall feed intake and improved feed conversion ratio with birds fed coarse 
particles showing a better growth performance. 
3. Feeding broilers diets containing up to 10%WB with coarse maize particles (1178μm) 
during the starter phase did not adversely affect average daily feed intake but improved 
average daily gain and feed conversion ratio. This shows diets influence good broiler 
weight gain as early as during the starter phase. 
4. Feed cost reduced as the levels of wheat bran increased with fine (725μm) or coarse 
(1178μm) maize particles with no adverse effect on overall growth performance and health. 
5. The carcass yield of experimental birds was not negatively affected by the inclusion of up 
to 17%WB with fine (725μm) or coarse (1178μm) maize particles. 
6. There was no proportional increase in caecal butyric acid concentration as WB level 
increased with fine (725μm) or coarse (1178μm) maize particles. Rather, there were higher 
concentrations of acetic acid in caecal content. 
7. There was no linear increase or decrease in the counts of Lactobacillus spp. or E. coli 
respectively as %WB increased with fine (725μm) or coarse (1178μm) maize particles. 
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Rather, there was a relative abundance of Lactobacillus spp which influenced the overall 
gut health of the broilers. 
8. Increasing the levels of wheat bran with fine (725μm) or coarse (1178μm) maize particle 
did not linearly reduce caecal pH even though an acidic environment was created. 
9. Feeding broilers up to 17%WB with fine (725μm) or coarse (1178μm) maize particles did 
not adversely affect villi height, crypt depth and villi to crypt depth ratio of the jejunum 
and ileum. Hence, effect nutrient absorption and utilization enhanced overall growth 
performance. 
10. The experimental treatments used in this study had no adverse effects on the 
haematological indices, serum glucose content and immune status of broilers, which is a 
good indication of good health. 
6.2. Recommendations 
1. Feed manufacturers can include up to 17% wheat bran with fine (725μm) or coarse 
(1178μm) maize particles in broiler diets in order to cut down feed cost, promote growth 
and gut health. 
2. Further studies should be carried out to establish a relationship, if any, between the roles 
dietary particle size uniformity and differences in geometric mean diameter play in broiler 
growth performance and gut health. 
3. Further investigations should be conducted to determine if: 
a. The influence of dietary particle size on broiler growth and gut health is affected 
by feed form. 
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b. Varying the dietary particle size and levels of inclusion of other commonly used 
agro-by products such cassava peels, copra cake and palm kernel cake in Ghana 
will enhance broiler growth, gut health and cost-effectiveness. 
c. Dietary fibre level (using wheat Bran as a DF source) s and dietary particle size has 
any influence on microbial diversity. This will enable effective formulation of diets, 
which will influence the ratio of gut microbes in order for specific short-chain acids 
to be produced. 
  
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