Dietary Antimicrobial Peptides Improve Intestinal Function, Microbial Composition and Oxidative Stress Induced by <i>Aeromonas hydrophila</i> in Pengze Crucian Carp (<i>Carassius auratus</i> var. <i>Pengze</i>)

There is increasing evidence for the potential use of antimicrobial peptides as dietary supplements and antibiotic substitutes. In this study, we analyzed the differential effects of varying levels of antimicrobial peptides on the intestinal function and intestinal microbial and disease resistance of Pengze crucian carp. Approximately 630 experimental fishes were randomized in the control group (G0: 0 mg/kg) and in five groups supplemented with different doses of AMPs (G1: 100 mg/kg, G2: 200 mg/kg, G3: 400 mg/kg, G4: 800 mg/kg, and G5: 1600 mg/kg) and were fed for ten weeks. Three replicates per group of 35 fish were performed. The results showed that AMPs promoted intestinal villus development and increased intestinal muscular thickness (p p p Firmicutes and Bacteroidetes increased in the AMP-supplemented groups, but the Firmicutes/Bacteroidetes ratio was lower than that in the G0 group. AMP supplementation also decreased the abundance of Fusobacterium while increasing the proportion of Actinobacteria (p Aeromonas hydrophila infection, the expression levels of anti-inflammatory factors in the intestinal tract of G3 animals were significantly upregulated, and the level of the proinflammatory factor was decreased (p Cetobacterium levels of G3 animals were significantly increased (p Proteobacteria levels were decreased, and the intestinal goblet cell proliferation was significantly lower than that of G0 animals (p < 0.05). This indicates that groups supplemented with AMPs have better disease resistance than the G0 group and can rapidly reduce the adverse effects caused by inflammatory response. Taken together, the present results suggest that AMP supplementation can improve intestinal function and intestinal microbial and pathogen resistance in Pengze crucian carp