Effects of chlorogenic acid in feed on the growth performance, digestive enzyme activity, immune function, and antioxidant capacity of loach (Misgurnus anguillicaudatus)

(Objective) Taking loach as the research object, the effects of different concentrations of chlorogenic acid added to the feed on the growth performance, digestive enzyme activity, immune function and antioxidant capacity of loach were studied. (Method) Disease free and injury free loach, weighing 3.50 ± 0.01g/tail, was randomly divided into 5 groups. The basic feed was supplemented with 0, 200, 400, 600 and 800 mg/kg chlorogenic acid test feed, and each group was repeated for 56 days. After feeding test, the growth performance, digestive enzyme activity, biochemical indicators, immune function and antioxidant capacity of loach (Misgurnus anguillicaudatus) were determined. (Results) Compared with the control group, the final weight (FBW), weight gain rate (WGR) and specific growth rate (SGR) of loach were significantly increased by adding chlorogenic acid to the diet (P < 0.05); The activities of protease, lipase and amylase in liver and intestine increased significantly (P < 0.05), total antioxidant capacity (T-AOC), catalase (CAT), superoxide dismutase (SOD), glutathione (GSH) and glutathione peroxidase (GSH-Px) increased significantly, and malondialdehyde (MDA) production decreased. The activities of aspartic acid transaminase (AST) and alanine transaminase (ALT) in liver increased with the increase of chlorogenic acid concentration, reaching the maximum at 400 mg/kg and 600 mg/kg respectively. With the increase of acid concentration, serum AST and ALT activities decreased significantly (P < 0.05), and serum lactate dehydrogenase (LDH) gradually decreased with the increase of chlorogenic acid concentration, reaching the lowest value at 400 mg/kg concentration; The content of complement 3 (C3) and complement 4 (C4) in serum increased first and then decreased, reaching the peak when the concentration of chlorogenic acid was 400 mg/kg and 600 mg/kg, respectively; the level of immunoglobulin M (IgM) in serum significantly increased (P < 0.05), reaching its maximum at a concentration of 600 mg/kg; serum lysozyme (LYS) content first increased and then decreased, reaching the maximum when the concentration was 400 mg/kg. (Conclusion) Adding 400,600 mg/kg chlorogenic acid to the diet can improve the antioxidant capacity of loach, significantly improve the growth performance and digestive enzyme activity of loach (P < 0.05), enhance the immune function of loach and the digestion and absorption of nutrients, and further protect the liver tissue of loach.