Water Temperature and Surface Coating Effect on Floatability, Water Absorption and Thickness Swelling of Feed

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).