Effects of dietary lipid levels on survival, growth performance, and antioxidant ability of the early juvenile Scylla paramamosain

Five isonitrogenous diets (50% crude protein) with 7%, 9%, 11%, 13%, and 15% lipid levels (named as L7, L9, L11, L13, and L15, respectively) were designed to evaluate the effects of dietary lipid levels on survival, growth performance, body composition, and antioxidant ability of the early juvenile Scylla paramamosain. Each diet was fed to three replicates of 28 crabs with initial weight 42.23 ± 0.21 mg for 8 weeks. Crabs fed diet with lowest dietary lipid level (L7 group) obtained significantly lower survival than other crabs. The highest final body weight (FBW), weight gain (WG), specific growth rate (SGR), and molting frequency (MF) were observed in L11 group. Meanwhile, the highest mRNA expression of ecdysone receptor (EcR) also observed in L11 group. Besides, a positive correlation between body lipid contents and dietary lipid levels was observed in present study. But the mRNA expression of fatty acid synthetase (FAS) was relatively lower in L15 group. In the hepatopancreas, superoxide dismutase (SOD) activity significantly increased with increasing dietary lipid levels. On the contrary, the concentration of malondialdehyde (MDA) significantly decreased with elevating dietary lipid levels (except L15 group). Meanwhile, the lowest catalase (CAT) activity appeared in L7 group, but there was no statistical difference from other groups. Through the second order polynomial regression equation analysis of WG, the optimum dietary lipid level in the early juvenile S. paramamosain was 10.31%.