Effects of dietary of bile acid on growth performance, antioxidant capacity, liver and intestinal health and immune function in loach (Misgurnus anguillicaudatus)

Bile acid (BA) play an important role in nutrient absorption and are key regulators of antioxidant and immune response homeostasis. The purpose of this study was to evaluate the effects of dietary supplementation with 0 (CON), 100 (BA100), 200 (BA200), 300 (BA300) and 400 (BA400) mg/kg BA on the growth, digestive enzyme activity, antioxidant capacity and immune response of loach. The results of serum biochemical analysis showed that the serum markers of liver damage (ALT, AST, ALP and LDH) of loach were decreased by adding BA. The BA diets mainly affected the lipase activity in the liver and intestine of loach, but there was no significant difference on protease. Histological section results showed that dietary supplementation with 100, 200 and 300 mg/kg BA increased the number of liver nuclei, liver vacuolation, intestinal wall muscle thickness and intestinal villi. In addition, BA enhanced the antioxidant capacity of loach by increasing the activities of GSH, GSH-Px, CAT, SOD and GST in their tissues (liver and intestine) and the mRNA expression levels of antioxidant-related genes (cat, gsh-px, sod and nrf2). At the same time, BA increased serum immune parameters (C3, C4, IgM and LYS), up-regulated the mRNA expression levels of anti-inflammatory factors (il-10), key immune genes (lys) and down-regulated the mRNA expression levels of pro-inflammatory factors (il-1β and tnf-α) in tissues (liver and intestine). In conclusion, dietary BA supplementation could improve the liver and intestinal digestive enzyme activities, enhance the antioxidant capacity and immune function, and promote the healthy growth of loach. Based on the results of these studies, the optimal supplementation of BA in loach diets was 200–300 mg/kg.