Dietary condensed tannin exhibits stronger growth-inhibiting effect on Chinese sea bass than hydrolysable tannin

Abstract

A 56-d feeding trial was carried out to assess the effects of dietary hydrolysable tannin (HT) and condensed tannin (CT) on growth performance, whole body composition, digestive enzyme activities, serum metabolites, antioxidant and immune response, and intestinal and liver histomorphology of Chinese sea bass (Lateolabrax maculatus). Four diets were formulated to contain 0 (T1), 2 g/kg of CT (T2), 2 g/kg of HT (T3), and 1 g/kg of CT plus 1 g/kg of HT (T4). A total of 640 fish were randomly divided into 16 tanks with 4 tanks per diet. Results showed that the final body weight, weight gain rate and specific growth rate were ranked as T1 > T2 > T4 > T3 (P < 0.05). Feed conversion ratio was ranked as T1 < T4 < T2 < T3 (P < 0.05). Compared to T2, feed intake was higher (P < 0.05) in T1 but lower (P < 0.05) in T3 and T4, intestinal trypsin, lipase and amylase activities were higher (P < 0.05) in T1 but lower (P < 0.05) in T3, the total cholesterol and triacylglycerol were higher (P < 0.05) in T1 but lower (P < 0.05) in T3, the aspartate aminotransferase was lower (P < 0.05) in T1 but higher (P < 0.05) in T3, the serum total antioxidant capacity, superoxide dismutase and lysozyme were lower (P < 0.05) in T1 but higher (P < 0.05) in T3. Intestinal villus and hepatocyte in T2, T3, and T4 had different degrees of injury. The villus length was higher (P < 0.05) but the villus width was lower (P < 0.05) in T1 than those in other groups. In summary, dietary 2 g/kg of CT and HT inhibited digestion, induced intestinal and liver injury and reduced growth of L. maculatus. Compared to HT, CT had stronger growth-inhibiting effect and damage on fish, suggesting CT should be chosen carefully as dietary supplement in L. maculatus.