Modulation of innate immunity, antioxidant capacity, intestinal barrier and disease resistant in common carp by dietary sodium acetate.

This study examined the effects of sodium acetate (SA) on immunity, antioxidant status, intestinal barrier function, and disease resistance in juvenile common carp. A 1-week short-term gavage trial was first conducted using SA concentrations of 0, 0.25%, 0.5%, 1.0%, 1.5%, and 2.0%. SA at various doses enhanced immune and antioxidant responses, with optimal gavage ranges of 0.87%-1.04% and 0.92%-1.20%, respectively. Subsequently, an 8-week feeding trial was performed with five groups: two controls (CK, CK+, 0% SA) and three SA-supplemented groups (0.5%, 1.0%, 1.5%), with three replicates per group (n = 30). After feeding, serum D-LA, ET-1, 5-HT and DAO did not differ significantly (P > 0.05). However, SA supplementation significantly increased immune indices [TNF-α (1.0%), IL-1β (0.5-1.5%), IL-6 (1.0-1.5%), IL-10 (1.0-1.5%), TGF-β (1.0%), NO (1.0-1.5%), LZM (1.0-1.5%), AKP (1.0-1.5%)], hepatopancreatic antioxidant parameters [T-AOC (1.5%), SOD (0.5%), CAT (0.5-1.5%), GSH-Px (0.5-1.0%), GSH (1.0-1.5%)], and intestinal tight junction gene expression [zo-1 (0.5-1.0%), occluding (0.5-1.5%), claudin-1 (0.5%)], while decreasing MDA (0.5-1.0%) (P < 0.05). After infection, Aeromonas hydrophila triggered inflammatory responses and oxidative stress by significantly elevating the contents of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) and NO, as well as the activities of LZM and AKP and related antioxidant indices (P < 0.05), down-regulating the expression of intestinal tight junction protein genes and increasing intestinal permeability, thereby impairing intestinal integrity and ultimately reducing the survival rate to 29.80% (P < 0.05). In contrast, dietary SA supplementation significantly reversed these changes: it reduced the levels or activities serum immune indicators, hepatopancreas antioxidant indices and intestinal permeability markers (P< 0.05). Moreover, the levels of anti-inflammatory cytokines (IL-10, TGF-β), the expression of intestinal tight junction proteins, and the survival rate were all significantly higher in the SA-supplemented group than in the infected control (CK+) group (P < 0.05). Collectively, these results demonstrate that dietary SA supplementation enhances innate immunity, antioxidant capacity, intestinal barrier function, and disease resistance in juvenile common carp, and the recommended dosage is 1.0%.