Effects of Dietary Lipid Levels on Growth Performance, Whole Body Composition and Digestive Enzyme Activity of Juvenile Bighead Carp (Aristichthys nobilis)

A 60-day study was conducted to investigate the effects of dietary lipid levels on growth, whole body composition and digestive enzyme activity of bighead carp (Aristichthys nobilis) with initial average weight (3.28 ± 0.11) g. Six isonitrogenous (40.25% crude protein) diets were formulated to contain graded contents of lipid (4.72%, 7.31%, 11.02%, 14.90%, 17.14%, and 19.37%) using corn oil and soybean oil as main lipid source. The results showed that the maximum weight gain (WG) and specific growth rate (SGR) were recorded at 11.02% dietary lipid level. Significant alterations were demonstrated on whole-body composition by different dietary lipid levels. Crude lipid content of whole body increased in parallel with the increase of dietary lipid levels. Fish fed diet with 11.02% lipid level showed lowest moisture and ash content. The activities of amylase and protease initially increased before decreasing, and the highest activities of amylase and protease were obtained in individuals fed the 11.02% lipid content diet. There were no significant differences in condition factor (CF) and hepatosomatic index (HSI) (P >0.05). Based on the polynomial regression analysis of WG and SGR, this study suggested that the optimum dietary lipid requirement of juvenile bighead carp was estimated to be 7.77%~8.31%.