Effect of dietary phosphorus on growth performance, body composition, antioxidant activities and lipid metabolism of juvenile Chinese mitten crab (Eriocheir sinensis)

This study investigated the effects of dietary phosphorus (P) on growth, body composition, antioxidant activities and lipid metabolism of juvenile Chinese mitten crab (Eriocheir sinensis). Six diets containing available P levels at 0.20%, 0.44%, 0.99%, 1.37%, 1.75% and 2.01% were prepared and fed to juvenile E. sinensis (0.38 ± 0.01 g) for 56 days. The weight gain, specific growth rate and molting frequency were markedly affected by dietary P, and the highest weight gain and specific growth rate were obtained in crabs fed the 0.99% available P diet. With increasing the dietary available P levels, the whole-body ash, Ca, and P contents, as well as the hepatopancreas and serum P contents increased, while the whole-body Mg content decreased. The increase of dietary P levels significantly decreased the lipid contents of whole-body, hepatopancreas and muscle, while increased the crude protein content of hepatopancreas. The hepatopancreas and serum alkaline phosphatase activities increased with an increase in dietary available P levels from 0.20% to 1.37%, and then decreased afterward. The crabs fed 1.37% available P diet had a markedly higher alkaline phosphatase activity than those fed 0.20%, 0.44% and 2.01% available P diets. Moreover, dietary P significantly affected total antioxidant capacity, the activities of total superoxide dismutase and glutathione peroxidase, and the malondialdehyde content in the hepatopancreas. The highest antioxidant activity and lowest malondialdehyde content in the hepatopancreas were found in the crabs fed 1.37% of available P in the diet. The relative mRNA expression showed that dietary P reduced hepatopancreas lipid accumulation might be produced through suppressing the genes related to lipid synthesis and promoting the genes related to lipid transport. This study demonstrates that optimum dietary P could enhance growth, antioxidant capacity and reduce hepatopancreatic lipid accumulation in juvenile E. sinensis and the range of available P in the diet is suggested to be 1.16%–1.51%.