FERMENTED AURANTII FRUCTUS IMMATURUS RESIDUE ON GROWTH PERFORMANCE, ANTIOXIDANT CAPACITY, AND INTESTINAL HEALTH IN BULLFROGS (LITHOBATES CATESBEIANUS)

This study aimed to investigate the effects of dietary supplementation with fermented Aurantii fructus immaturus residue (FAFI) on growth performance, antioxidant capacity, liver health, immune response, and gut microbiota in bullfrogs (Lithobates catesbeianus). A total of 480healthy L. catesbeianus with an initial body weight of (9.60±0.10) g were randomly allocated into two groups: a control group (CON) fed a basal diet, and an experimental group (5% FAFI) fed the basal diet supplemented with 5% FAFI for 56d. Compared to the CON group, the 5% FAFI group showed significantly improved final body weight and weight gain rate (P<0.05). Digestive enzyme activities and intestinal morphology were also enhanced (P<0.05). Serum activities of ALT and AST, and the contents of TC and TG were significantly decreased (P<0.05), while AKP and ACP activities were markedly increased (P<0.05). Hepatic antioxidant assessment revealed significantly elevated activities of SOD, CAT, GSH, and up-regulated expression of related genes (sod, cat, gsh-px, gstp) (P<0.05), alongside a reduction in MDA content (P<0.05). Intestinal gene expression analysis indicated suppressed pro-inflammatory cytokines (tnf-α, il-1β) and significantly elevated anti-inflammatory cytokine (il-10) (P<0.05). The Richness index and Chao1 index of the intestinal microbiota in the 5% FAFI group were significantly lower than those in the CON group (P<0.05). At the phylum level, the abundance of Firmicutes (76.14%) and Proteobacteria (23.10%) in the 5% FAFI group was slightly higher than that in the CON group (75.59%, 20.87%). At the genus level, the relative abundance of Lactococcus was significantly increased (P<0.05), while multiple potentially pathogenic bacterial genera, such as Citrobacter and Edwardsiella, showed a decreasing trend. In conclusion, dietary supplementation with 5% fermented Aurantii fructus immaturus residue can effectively enhance growth performance and overall health in bullfrogs by improving antioxidant capacity, modulating liver metabolism, regulating immune responses, and optimizing the structure of the intestinal microbiota.