Effects of dietary Zn on growth, antioxidant capacity, immunity and tolerance to lipopolysaccharide challenge in juvenile Chinese mitten crab Eriocheir sinensis

Zinc (Zn) is an essential trace mineral element in organisms and is involved in physiological processes. This study investigates the effects of dietary Zn on the growth, antioxidant capacity, non-specific immunity and disease resistance of juvenile Chinese mitten crab. Zn was supplemented, respectively, at 0 (control), 25, 50, 100, 200 and 400 mg/kg to the basal diet to form six diets as Zn0, Zn25, Zn50, Zn100, Zn200 and Zn400. Each diet was separately used to feed the crabs (0.40 ± 0.01 g) for 56 days. Diet without Zn supplementation led to a higher feed intake rate, a lower Zn content in the hepatopancreas and a lower non-specific immune enzyme activity than other groups with Zn supplement. The results also showed that compared with the control group: (1) The final weight, weight gain rate, specific growth rate, Zn in the hepatopancreas, body crude protein and the activities of serum alkaline phosphatase (AKP), acid phosphatase (ACP) and copper-zinc superoxidase (CuZnSOD) were significantly increased in the Zn100 group. (2) Moreover, Zn accumulation in the hepatopancreas and body ash were significantly increased in the Zn200 group, and the antioxidant enzyme activities such as CuZnSOD and glutathione peroxidase (GSH-Px) in the hepatopancreas were significantly increased. (3) In addition, the addition of Zn can activate the TLRs/NF-κB pathway after the lipopolysaccharide (LPS) injection, resulting in upregulation of the relative mRNA expression of antimicrobial peptide (ALFs). This study demonstrates that dietary Zn supplements can significantly improve growth performance, antioxidant capacity, non-specific immunity and disease resistance of juvenile crabs. The regression analysis showed that the optimal dietary Zn level was 94.87 mg/kg for weight gain and 96.96 mg/kg for specific growth.