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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. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of dietary myo‐inositol (MI) levels on growth, body composition, antioxidant status, non‐specific immunity and lipid metabolism in juvenile Chinese mitten crab (Eriocheir sinensis). A total of 960 crabs was fed with six diets supplemented with graded levels of MI (0, 204, 406, 810, 1,650 and 3,211 mg/kg) for 8 weeks. The crabs fed with diets containing 1,650 mg/kg MI had significantly higher final body weight, weight gain and specific growth rate than those fed 0, 204, 406 and 810 mg/kg MI (p <.05). The lowest moulting frequency was observed in the crabs fed diets without supplemented MI. The crabs fed with diets containing 1,650 and 3,211 mg/kg MI had significantly lower total lipid content in the whole body than those fed diets without supplemented MI (p <.05). The myo‐inositol level in hepatopancreas increased with increasing dietary MI up to 1,650 mg/kg before reaching plateau. The crabs fed 1,650 mg/kg MI had significantly higher total antioxidant capacity and glutathione peroxidase activity in hepatopancreas than those fed diets without supplemented MI (p <.05). However, the crabs fed diets without supplemented MI had the highest level of malondialdehyde in hepatopancreas compared with those fed with MI supplementation. The highest serum alkaline phosphatase activity was also observed in crabs fed 1,650 mg/kg MI. Total protein and haemocyanin contents in serum were significantly increased with increasing dietary MI levels (p <.05). The triglyceride contents in hepatopancreas significantly decreased with increasing dietary MI levels (p <.05). Results of real‐time quantitative PCR revealed that dietary MI reduced hepatic triglyceride accumulation probably through inhibiting lipid synthesis‐related genes and promoting lipid export‐related genes at the transcriptional level. Broken‐line analysis of weight gain, specific growth rate and MI levels in hepatopancreas against dietary MI levels indicates that the optimal MI requirement for juvenile crabs ranged from 1,613 to 1,707 mg/kg. The dietary MI supplementation can improve growth performance, antioxidant capacity and non‐specific immunity and reduce hepatopancreatic triglyceride accumulation in juvenile crab. [ABSTRACT FROM AUTHOR]