Effects of three feeding modes on the metabolism, antioxidant capacity, and metabolome of the adult male Chinese mitten crab Eriocheir sinensis

Natural diets and traditional diets have been gradually replaced with formulated diets for the Chinese mitten crab Eriocheir sinensis culture, but it is unclear what effect the different feeding modes have on digestive physiology and metabolism of E. sinensis. This study investigated the effects of three feeding modes, formulated diets (FD, feeding with formulated diets), natural diets (ND, feeding with trash fish and fresh snail), and traditional diets (TD, feeding with soybean, wheat, broad bean, and corn) on the metabolism, antioxidant, and immune capacity of adult male E. sinensis. The results showed that the highest activities of lipase, trypsin, gamma-glutamyltransferase, superoxide dismutase, acid phosphatase, alkaline phosphatase, and the contents of urea and malondialdehyde in the hepatopancreas, as well as the levels of triglyceride, uric acid, and malondialdehyde in the hemolymph supernatant, were detected in the ND mode, while the highest hemolymph supernatant free cholesterol was detected in the TD mode. The hemolymph supernatant glucose content of males from the FD mode was significantly lower than that of the ND and TD modes. Metabolomics analysis showed that feeding mode induced significant differences in the metabolite profiles of the hepatopancreas and hemolymph supernatant, where differential metabolites were mainly involved in amino acid and glucose metabolism. Compared with the ND and TD modes, the FD mode was more conducive to the digestion, absorption, and deposition of amino acids and glucose. Overall, this study demonstrated that feeding formulated diets that contain more balanced nutrient profiles improved nutrient utilization, antioxidant capacity, and immune indices of adult male E. sinensis.