Effects of dietary chitinase on growth, non-specific immunity, antioxidative capacity and intestinal health of juvenile Chinese mitten crab ( <i>Eriocheir sinensis</i> )

The present study aims to investigate the effects of dietary chitinase on the growth, non-specific immunity, antioxidative capacity, and intestinal health of juvenile Chinese mitten crab ( Eriocheir sinensis ). A control diet (D1) was designed with 200 g/kg fish meal and 28 g/kg chitin content. Then, 5, 10, 15, and 20 g/kg chitinase were respectively added to the control diet, abbreviated as D2, D3, D4, and D5, to prepare five groups of isonitrogenous and isolipid diets. These diets were fed to juvenile crabs with an initial body weight of 1.55 ± 0.10 g for 56 days. The results showed that the FW, WG, survival, HSI, MI, whole crab protein content, and hepatopancreas (HP) protease and lipase activities were significantly positively linearly correlated with the dietary chitinase level (P &lt; 0.05). The activities of serum ACP, LZM, ALP, T-SOD, GSH-Px, T-AOC, and CAT were significantly positively linearly correlated with dietary chitinase level (P &lt; 0.05). The intestinal fold height of E. sinensis exhibited a significant linear positive correlation with the dietary chitinase content (P &lt; 0.05). The intestinal fold height was relatively lower in crabs from groups D1 and D2, with some simple columnar cells failing to bulge to form folds. In contrast, the intestinal epithelial cells of crabs in groups D3, D4, and D5 all bulged to form folds, and the fold height was significantly higher than that in group D1 (P &lt; 0.05). The abundance of Brevibacterium , a harmful bacterial genus in the intestine, exhibited a significant linear negative correlation with dietary chitinase levels (P &lt; 0.05). In conclusion, the supplementation of chitinase in the control feed improved the growth performance, non-specific immunity, anti-oxidative capacity, and intestinal health of E. sinensis , with the optimal addition level ranging from 15 - 20 g/kg.