Effect of Varying Dietary Lipid Levels on Growth, Feed Conversion, Nutrient Retention and Carcass Composition of Fingerling Catfish, Heteropneustes fossilis

Casein-gelatin based purified diets ( 40% CP, 18 kJ·g·1 GE) with graded levels (3,5,7,9,11 and 13%) of lipid were fed to fingerling Heteropneustes fossilis to Investigate changes in growth, feed conversion, nutrient retention and carcass composition. Fish stocked in triplicate sets of 15 fish each, in 70 I flow-through (1.0-1.5 l ·min-1 ) type polyvinyl circular troughs, were fed diets at the rate of 4% body weight-day-1• Over the six-week growth trial, maximum gain in live weight (194%), specific growth rate (2.57%), protein efficiency ratio (1.76) and best feed gain ratio (1.44) were noted in fish at 7% lipid intake. Moisture, crude protein, fat and gross energy contents of carcass were significantly (P<0.05) affected by diet. Although carcass protein and percent protein retention increased up to 7% dietary lipid level, dry matter, crude fat, gross energy and percent GE retention registered a constant increase with dietary lipid levels. The tendency of fat deposition at each incremental dietary lipid level was found to be more pronounced in viscera than in muscle. The hepatosomatic index was not correlated to dietary lipid levels. It was concluded that H. fossilis requires a level of 7% lipid as an energy source in 40% CP diet, with 18.2±0.21 kJ·g-1 of gross energy and a carbohydrate-to-lipid ratio of about 5 for maximum utilization and growth.