Effect of Different Dietary Protein and Lipid Levels on the Growth,Body Composition,and Intestinal Digestive Enzyme Activities of Juvenile Yellow Drum Nibea albiflora(Richardson)

An 8-week feeding trial was conducted to determine the optimal dietary protein-to-lipid ratio for juvenile Nibea albiflora with an initial weight of（11.76 ± 0.20） g.Nine experimental diets containing different concentrations of protein（40%,47%,or 54%） and lipids（5%,9%,or 13%） in a 3 × 3 factorial experimental design were tested in triplicate groups of fish,while the protein-to-energy（P/E） ratios of the diets varied in the range of 19.74–28.32 mg k J-1.Results showed that fish fed diets containing 9% or 13% lipids with 54% protein exhibited significantly higher weight gains and specific growth rates than those fed other diets.The feed conversion rate of fish fed the diet with 40% protein and 5% lipids was significantly poorer than that of fish fed other diets.The protein efficiency rate of fish fed diets with 5% lipids was significantly lower than that of fish fed 9% or 13% lipid diets.Carcass lipid and energy contents were positively correlated with dietary lipid level regardless of protein level.Fish fed a 54% protein diet showed the highest trypsin activity.The intestinal lipase activity of fish fed the diet containing 13% lipids was significantly higher than that of fish fed 5% or 9% lipid diets.These results demonstrate the high protein dietary requirements of N.albiflora.A diet containing 54% protein and 9%–13% lipids with a P/E ratio of 26.2–27.81 mg protein k J-1 can be considered optimal for juvenile N.albiflora.