Abstract
Ten experimental diets were formulated to meet the 40% crude protein requirement of the African mudcatfish, Clarias gariepinus. In six of the diets fishmeal served as the main protein source while in the remaining four diets fishmeal was supplemented with either GNC or soybean cake to make isonitrogenous diets. The binding efficiency and some physical properties of diets formulated from each of the five binders: rice bran, brewery distiller grain (BDG), corn bran, soybean and groundnut cake (GNC) were assessed. Any of the other binders was used when either soybean or groundnut cake was not included in the diet. Ingredients were ground and sieved to a particle size of 350µm. Three mash conditioning methods: cold water, warm water and cold water with oil coating of pellets were used for mixing each set of ten diets. Physical parameters and binding efficiency were evaluated using floatability, bulk density (BD), water absoption index (WAI) and thickness swelling (TS). Feed with rice bran had the highest floatability with the least BD,WAI and TS. Feed with groundnut had the highest BD, WAI and TS and the least floatability. Mash conditioning with warm water gave a higher floatability over those with cold water but coating of feed with oil after cold water conditioning gave the highest floatability. There is direct relationship between floatability and bulk density (BD) and between floatability and water absorption index (WAI).
Highlights
In order to promote good health and attain maxium production, fish has to be fed
The results from this study showed that the ingredients used in feed formulation affect pellet characteristics
Sinnce rice bran gave the highest floatability, it served as source of starch and as a good binder giving the least water absorption index (WAI) and thickness swelling (TS). Both groundnut cake (GNC) and soyabean have the same quantity of crude protein, their bulk density differs, this affects the floatability of the diets
Summary
In order to promote good health and attain maxium production, fish has to be fed. Fish nutrition is critical to aquaculture as it represents 40 – 50% of the production costs. Over 90% of the feed used for livestock such as sheep, cattle, pigs and poultry is in mash form. Compounded feeds are preferred for fish and shrimp due to the peculiar solvent property of water (FAO, 1990). There has being development and the use of manufactured or artificial diets (formulated feeds) to supplement or to replace natural feeds in the aquaculture industry (FAO, 1997). Feed formulation and preparation is the process of combining feed ingredients to form a mixture that will meet the specific goals of production. Pellet durability and efficiency can be substantially improved by proper steam conditioning of mash. In this study the physical properties of feed formulated for the African catfish, Clarias gariepinus, using different binders and three mash conditioning methods were assessed
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