Effect of single and combined immunostimulants on growth, anti-oxidation activity, non-specific immunity and resistance to Aeromonas hydrophila in Chinese mitten crab (Eriocheir sinensis)

This study evaluates the effect of dietary supplementation of immunostimulants on the Chinese mitten crab (Eriocheir sinensis) with a single administration of mannan oligosaccharide (MOS), or its combination with either β-glucan or with inulin for 8 weeks. Four diets included an untreated control diet (C), MOS alone (3 g kg−1, M), MOS with β-glucan (3 g kg −1 MOS + 1.5 g kg −1 β-glucan, MB), and MOS with inulin (3 g kg −1 MOS + 10 g kg −1 inulin, MI). The weight gain and specific growth rate of the crabs fed M, MB, and MI diets were improved by lowing feed conversion ratio. The growth and feed utilization of the crabs fed the MB diet were improved compared with the other three groups. The crabs fed the M, MB and MI diets showed a higher intestinal trypsin activity than that in the M and control groups. The highest trypsin activity in the hepatopancreas was observed in the MB group. Crabs fed M, MB and MI diets increased antioxidant system-related enzyme activities, but reduced malondialdehyde. The highest activities of alkaline phosphatase, acid phosphatase, lysozyme and phenol oxidase in the gut and the respiratory burst of the crabs were found in the MB group. The MB diet promoted the mRNA expression of E. sinensis immune genes (ES-PT, ES-Relish, ES-LITAF, p38MAPK and Crustin) compared with the control. After 3 days of infection with Aeromonas hydrophila, the highest survival of crabs was also found in the MB group. This study indicates that the combination of MOS with β-glucan or with inulin can improve growth, antioxidant capacity, non-specific immunity and disease resistance in E. sinensis.