Effects of Dietary Chitosan on Growth, Antioxidant Capacity, Non-Specific Immunity, and Intestinal Health of the Mud Crab, Scylla paramamosain

This study investigated the effects of dietary chitosan supplementation at levels of 0, 0.5, 1, 2, 4, and 8 g/kg on the mud crab (<i>Scylla paramamosain</i>) during an eight-week feeding trial. Results revealed significant improvements in final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) as chitosan levels increased, with the 2 g/kg group showing the strongest effects (<i>p</i> < 0.05). Chitosan supplementation also elevated crude protein content in the whole body, muscle, and hepatopancreas (<i>p</i> < 0.05). Moreover, it notably reduced malondialdehyde (MDA) levels in hemolymph and hepatopancreas while enhancing antioxidant enzyme activity (<i>p</i> < 0.05). Chitosan at doses of 1-4 g/kg also significantly increased the activity of non-specific immune enzymes in hemolymph (<i>p</i> < 0.05). Additionally, chitosan enhanced mRNA expression of immune-related genes in the hepatopancreas (<i>p</i> < 0.05). According to gut microbiota study, 2 g/kg chitosan raised the relative abundance of advantageous gut bacteria and modulated microbial composition. In conclusion, appropriate dietary chitosan supplementation successfully stimulates mud crab growth, strengthens immunological and antioxidant systems, and improves intestinal health.