Effects of Dietary Fermented Chinese Herbal Waste Compound on the Growth, Digestive Function, Antioxidative Capacity and Non-Specific Immunity of Juvenile Largemouth Bass (Micropterus salmoides)

This study evaluated the effects of dietary fermented Chinese herbal waste compound (FCHW, comprising fermented stems and leaves of Astragalus membranaceus, Rheum tanguticum, and Bupleurum chinense) on the growth, digestive function, antioxidative capacity, and non-specific immunity in juvenile largemouth bass (Micropterus salmoides). Fish were randomly assigned to one of three dietary treatments for 45 days: a basal diet (control), a basal diet supplemented with 1% Chinese herbal waste (CHW), and a basal diet supplemented with 1% FCHW. The results showed that, compared to the control group, dietary FCHW significantly enhanced weight gain rate (WGR), specific growth rate (SGR), hepatic antioxidant enzyme activities (SOD, CAT, and GSH-Px), and hepatic non-specific immune parameters (ACP and AKP activities) of M. salmoides on both day 30 and day 45 (p < 0.05) except CAT activity on day 30. FCHW supplementation also significantly increased intestinal villus height, width, and muscularis thickness at both time points (p < 0.05). However, intestinal digestive enzyme activities (trypsin, lipase, and amylase) were elevated significantly only on day 30 relative to the control (p < 0.05). Dietary CHW showed limited efficacy. Compared to the control group, dietary CHW supplementation significantly improved intestinal lipase activity and hepatic SOD activity on day 30 (p < 0.05). By day 45, dietary CHW supplementation significantly increased intestinal morphology (villus height, width, and muscularis thickness) (p < 0.05). These results indicate that fermentation enhances the bioactivity of CHW, thereby supporting the potential of FCHW as a functional feed additive in aquaculture.