Effects of antimicrobial peptides on the growth performance, antioxidant and intestinal function in juvenile largemouth bass, Micropterus salmoides

Abstract

Antimicrobial peptides (AMPs) are small proteins with broad-spectrum antimicrobial activities, and could kill a variety of pathogens. In this study, 50 mg/kg (G1 group), 100 mg/kg (G2), and 200 mg/kg (G3) of AMPs were added to the basal diet (0 mg/kg AMPs, G0 group) of the largemouth bass (Micropterus salmoides). After feeding for 60 days, the growth performance, muscle composition, the activities of antioxidase immune-related enzymes and digestive enzymes, and intestinal morphology of M. salmoides were measured. The results showed that the final weight, weight gain rate, and specific growth rate were significantly higher in the G3 group than in the control group (G0) (p < 0.05). The crude protein of muscle in G3 group was significantly higher than in G0 group (p < 0.05). The crude lipid of muscle in AMPs supplement groups were significantly lower than in G0 group (p < 0.05). The total antioxidant capacities and catalase activities were significantly higher in the livers in all the AMPs supplement groups than in the G0 group (p < 0.05). Superoxide dismutase activities were significantly higher in the livers in the G2 and G3 groups than in the G0 group (p < 0.05). Glutathione peroxidase activities were significantly higher in the livers in the G1 and G3 groups than in the G0 group (p < 0.05). Malondialdehyde level was significantly lower in the livers in the G3 group than in the G0 group (p < 0.05). Trypsin activity in the intestines and pepsin activity in the stomachs were significantly higher in the G3 group than in the G0 group (p < 0.05). Amylase activity in the intestines was significantly lower in all the AMPs supplement groups than in the G0 group (p < 0.05). Lipase activity in the intestines was significantly higher in the G1 and G3 groups than in the G0 group (p < 0.05). The villus length and width were significantly higher in the G2 group than in the G0 group (p < 0.05). The villus diameter was significantly higher in all the AMPs supplement groups than in the G0 group (p < 0.05). The intestinal wall thickness was significantly greater in the G3 group than in the G0 group (p < 0.05).In conclusion, 200 mg/kg of AMPs in the diets of M. salmoides could promote growth performance, improve oxidation resistance and immunities, increase digestive enzyme activities and intestinal morphology.