Beneficial effects of Ginseng polysaccharide improve the growth performance, intestinal immunity, intestinal microbiota, and resistance to Yersinia ruckeri in channel catfish (Ictalurus punctatus).

This study evaluated the effects of ginseng polysaccharide (GP) supplementation on the growth performance, immunity, intestinal microbiota, and antibacterial activity of channel catfish (Ictalurus punctatus). Over a 56-day feeding trial, 750 catfish (60.03 ± 0.5 g) were fed diets containing GP at five concentrations: 0 mg/kg (CON), 200 mg/kg (GP200), 400 mg/kg (GP400), 800 mg/kg (GP800), and 1600 mg/kg (GP1600). GP supplementation at 200-800 mg/kg significantly enhanced growth performance, digestive enzyme activities (amylase, lipase, and trypsin), and reduced the feed conversion ratio (P < 0.05). The treatment significantly enhanced transcriptional activation of epithelial barrier-associated genes (zo-1, zo-2, and occludin), upregulated immunoregulatory mediators (tgf-β1, tgf-β2, tgf-β3, and il-10), and modulated key immune signaling pathways (tlrs, nf-κb, and Nrf2-keap1), Conversely, it suppressed pro-inflammatory signaling molecules (il-1β, il-8, tnf-α, and nf-κb) (P < 0.05). Additionally, GP supplementation improved intestinal histology (villus height, muscular thickness, and goblet cell numbers) and enriched beneficial gut microbiota, particularly Lactococcus and Weissella. Metabolic pathways related to phenylalanine metabolism and fatty acid degradation were also enhanced. In a bacterial challenge with Yersinia ruckeri, dietary supplementation with GP significantly enhanced survival outcomes in treated groups compared to the CON group (P < 0.05). These results indicate that GP supplementation at 200-800 mg/kg promotes growth performance, strengthens intestinal health, modulates immunity, and enhances resistance to bacterial infections in channel catfish.