Evaluation of Farm-Made and Commercial Fish Diets for Hapa Culture of Nile Tilapia (Oreochromis Niloticus L.) in Ghana Francis Assogba Anani

Abstract

One of the major constraints to aquaculture development and expansion in Ghana is affordable nutritionally balanced and cost effective fish diet. Although some fish farmers produce their own farm-made fish diets, these diets do not meet the nutritional requirements of the cultured fish as the farmers do not follow the appropriate feed formulation protocol. This study was carried out to generate information on the commercial fish diets and feed ingredients currently used by small-scale pond fish farmers in five major pond fish farming Regions (Ashanti, Brong-Ahafo, Central, Volta and Western) in Ghana. Six of the commonly used ingredients by the farmers were selected and used to formulate and prepare farm-made tilapia diets which were evaluated against two commonly utilised commercial tilapia diets for Nile tilapia (Oreochromis niloticus). In all, five diets namely A (farm-made diet supplemented with vitamin-mineral premixes, lysine and methionine), B (farm-made diet without supplements), C (commercial tilapia diet, Coppens), D (commercial tilapia diet, Raanan) and E (mixture of B and Raanan in a ratio of 1:1). The first part of the study was conducted in net hapas installed in a 0.2 hectare earthen pond over a 140-day growth period at the Aquaculture Research and Development Centre (ARDEC), Akosombo. O. niloticus with an initial mean weight of 22.8 ± 2.1 g were stocked at a density of 2 fish m-2 and fed at 4-3 % body weight three times a day. The second part of the study involved digestibility of the diets and this was carried out in plastic tanks with 20 L of water each for 20 days. After the culture period, the final mean weights of O. niloticus were 140.3 ± 23.4, 131.0 ± 24.4, 148.3 ± 25.4, 187.6 ± 42.1 and 140.7 ± 28.5 g for A, B, C, D and E respectively. There was no significant difference (p > 0.05) in specific growth rates among all the dietary treatments. Apparent nutrient digestibility coefficients were high (> 60 %) in all the dietary treatments. Crude protein ranged from 77.49 to 87.02 %, crude lipid ranged from 81.46-93.90 % whilst carbohydrate (nitrogen free extract) ranged from 65.28 to 85.94 %. Higher crude protein depositions and lower fat contents were observed in the carcass of fish fed farm-made diet A and Raanan. There were no internal and external abnormalities in O. niloticus fed with the various diets. Both the farm-made and commercial diets did not impact negatively on water quality. In terms of cost-effectiveness, the farm-made diets were more profitable than the commercial ones. The results indicated that nutritionally balanced farm-made fish diet is cost-effective and will boost growth of aquaculture in rural areas where semi-intensive pond aquaculture is mainly practised in Ghana. The current fish production (2 500 kg ha-1 yr-1) by Ghanaian small-scale pond fish farmers could increase up to a fourfold by using appropriately formulated and prepared farm-made fish diets with locally available ingredients. This is likely to increase their profit margin to over four hundred percent of what they are making currently using commercial fish diets. The costs associated with the use of commercial fish diets by small-scale pond fish farmers are high, and in terms of fish growth and economic returns, the use of appropriately formulated and prepared farm-made diets will be a better alternative. Fish farmers should be trained on the formulation and preparation of nutritionally balanced and cost effective farm-made fish diets so as to reduce their production cost and increase their profit margin.