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 kJ−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 kJ−1 can be considered optimal for juvenile N. albiflora.