Condensed Tannins Protect Against Aflatoxin B1-induced Toxicity in Lateolabrax Maculatus by Restoring Intestinal Integrity and Regulating Bacterial Microbiota

Condensed tannins (CT) have been shown to enhance the exogenous stress resistance of fish, whereas the protective effects of CT against damage induced by dietary aflatoxin B1 (AFB1) on the growth and health of fish have not been evaluated. A 56-day feeding trial was carried out to assess the effects of CT on alleviating dietary AFB1- induced damages in growth, antioxidant and immune response, intestinal integrity and bacterial microbiota of the Chinese sea bass (Lateolabrax maculatus). Three diets were formulated to contain 0 mg/kg of AFB1 and 0 g/kg of CT (G1), 1 mg/kg of AFB1 and 0 g/kg of CT (G2), and 1 mg/kg of AFB1 and 1 g/kg of CT (G3), respectively. Each diet was randomly assigned to three tanks with 40 fish in each tank. Fish were fed to apparent satiation twice daily. Results indicated that fish fed G2 had lower (P < 0.05) final body weight, weight gain rate, specific growth rate, feed intake, viscerosomatic index, total antioxidant capacity, superoxide dismutase, catalase, alkaline phosphatase and lysozyme, but higher (P < 0.05) malondialdehyde, diamine oxidase and lipopolysaccharide compared to those of fish fed G1 and G3. Fish fed G3 had higher (P < 0.05) villus length and intestinal tight junction protein gene expression (ZO-1, Claudin-3 and Occludin), but lower (P < 0.05) villus width than G2. Fish had similar growth performance, serum parameters and intestinal morphology between G1 and G3. In the top 10 dominant genera of intestinal microbiota, the relative abundance of Pseudomonas was higher in G2 but lower in G3 than in G1 (P < 0.05). Compared with G1, G2 and G3 had higher relative abundances of Aeromonas and Klebsiella, but lower relative abundance of Plesiomonas (P < 0.05). Dietary treatments did not alter the alpha and beta diversity of bacterial communities. In conclusion, dietary inclusion of 1 mg/kg of AFB1 reduced feed intake and decreased growth of L. maculatus. AFB1 reduced serum antioxidant capacity and immunity, increased intestinal permeability, induced intestinal damage and altered bacterial microbiota of fish. Supplementation of 1 g/kg of grape seed CT effectively protected against AFB1 toxicity by alleviating the negative impacts of dietary AFB1 exerted on fish. This study provides a rational for the application of CT in aquaculture to prevent fish from AFB1-induced damage.