Effects of myo-inositol on growth performance, body composition, antioxidant status, non-specific immunity and lipid metabolism of juvenile Chinese mitten crab (Eriocheir sinensis)

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.