Cecropin supplementation improves growth performance by regulating immune function, rumen fermentation and microbiota in goats

Objective: This study aimed to determine the effects of cecropin on the growth performance, antioxidant capacity, immune function, rumen fermentation parameters, and rumen microbiota of goats. Methods: Twelve male Yudong black goats were randomly divided into two groups, with 6 replicates per group. The control group (CON) was fed a basic diet, while the antimicrobial peptide group (AMP) received a diet supplemented with 500 mg/kg cecropin. The experimental period lasted for 60 days. Results: Compared with the CON group, the AMP group showed significantly improved FW (35.46 vs. 37.33 kg, p<0.05), average daily gain (205.19 vs. 234.78 g/d, p<0.05), and reduced feed-to-gain ratio (6.45 vs. 5.66, p<0.05). The AMP group presented significantly higher SOD, GSH-Px, and CAT activities and total antioxidant capacitylevels in the serum, while the MDA content was significantly lower (p<0.05). Furthermore, compared with the CON group, the levels of IgG, IgA, and IL-10 in the AMP group were significantly increased, while the levels of IL-2, IL-6, IL-1β, and TNF-α were significantly decreased (p<0.05). In the rumen fluid, the AMP group presented significantly greater propionate and total volatile fatty acid levels, with a significantly lower acetate/propionate ratio (p<0.05). Microbial analysis revealed differences in rumen microbiota diversity and composition between the two groups. At the phylum level, the AMP group presented significantly greater abundances of Bacteroidota, Fibrobacterota, Desulfobacterota, and Elusimicrobiota, whereas the Firmicutes abundance was significantly lower than that in the CON group (p<0.05). At the genus level, the AMP group presented significantly greater abundances of Prevotella, Rikenellaceae_RC9_gut_group, F082, Fibrobacter, Prevotellaceae_UCG-003, Bacteroidales_RF16_group, Christensenellaceae_R-7_group, and UCG-010, whereas the abundances of Prevotellaceae_UCG-001 and Butyrivibrio were significantly lower (p<0.05). Conclusion: Overall, these results suggest that adding 500 mg/kg cecropin to the diet promotes goat growth performance by improving serum antioxidant capacity and immune function, optimizing rumen fermentation parameters, and modulating rumen microbiota.