Dietary <scp>N‐Acetylserotonin</scp> offers protection against <i>Shewanella putrefaciens</i> infection in <scp>Chinese</scp> mitten crab <i>Eriocheir sinensis</i>

Abstract Shewanella putrefaciens is an important bacterial pathogen that poses a serious threat to Chinese mitten crab ( Eriocheir sinensis ) aquaculture. However, the protective effects of N‐Acetylserotonin (NAS) against S. putrefaciens infection in E. sinensis remain unknown. In this study, to evaluate the protective effects of NAS while eliminating the influence of dimethyl sulfoxide (DMSO) as its solvent, the growth performance, hepatopancreatic immunity, antioxidant capacity, intestinal microbiota, and resistance to S. putrefaciens challenge were assessed in E. sinensis from the blank control, 10.0 mL/kg diet of DMSO‐treated negative control, and 10.0 mL/kg diet of DMSO +0.5 and 1.0 g/kg diet of NAS‐treated groups. The results showed no significant differences in the growth performance among crabs in the blank control, 10.0 mL/kg diet of DMSO‐treated negative control, and 10.0 mL/kg diet of DMSO +0.5 and 1.0 g/kg diet of NAS‐treated groups. The hepatopancreatic acid phosphatase, alkaline phosphatase, lysozyme, superoxide dismutase, and catalase activities of the 10.0 mL/kg diet of DMSO +0.5 and 1.0 g/kg diet of NAS‐treated crabs were significantly increased compared with the blank control. In contrast, no significant changes were observed for these enzyme activities in the 10.0 mL/kg diet of DMSO‐treated negative control crabs. Furthermore, the 10.0 mL/kg diet of DMSO +0.5 and 1.0 g/kg diet of NAS‐treated crabs exhibited a notable improvement in the richness and diversity of intestinal microbiota and displayed survival rates of 36.67% and 60.00%, which were significantly higher than the blank control and 10.0 mL/kg diet of DMSO‐treated negative control groups. Collectively, these findings reveal that NAS shows great promise as a potential prophylactic agent for health maintenance and disease prevention in crab culture.