Effects of dietary supplemented with a combination of magnolol, palmatine and β-glucan on growth rate, antioxidant activity, immune response and resistance to Aeromonas hydrophila in tilapia (Oreochromis niloticus)

This study evaluated the effects of dietary additions of magnolol, palmatine and β-glucan mixture on growth rate, antioxidant capacity, immune response and resistance to Aeromonas hydrophila in tilapia (Oreochromis niloticus). Four experimental diets were formulated with 0 %, 0.24 %, 0.48 % and 0.96 % compound additives (magnolol: palmatine: β-glucan = 1:1:10) and fed for ten weeks. The addition of compound additives did not affect the growth indices but improved the protein efficiency ratio of tilapia. Feeding 0.24 % or 0.48 % compound additives increased the blood leukocyte and basophil as well as erythrocyte and hemoglobin contents, respectively. However, the addition of 0.24–0.96 % compound additives decreased the serum total cholesterol and LDL-C levels, as well as the LDL-C/HDL-C and AST/ALT ratios. In addition, supplementation with 0.24–0.48 % compound additives increased the activities of glutathione reductase, superoxide dismutase, peroxidase and total antioxidant capacity in the intestine, plasma, and liver, but reduced the content of malondialdehyde, thereby enhancing the antioxidant capacity of tilapia. Further, the inclusion of 0.24–0.48 % compound additives enhanced the plasma immunoglobulin M, complement 4, complement 3 levels as well as lysozyme activity. The phagocytic activity of head kidney macrophages was improved by supplementation with 0.48 % compound additives. Besides, the addition of 0.48 % compound additives reduced the cumulative mortality and thereby increased the relative protection rate of tilapia infected with A. hydrophila. Under the present experimental conditions, the addition of 0.24–0.48 % compound additives was effective in improving the antioxidant capacity, immune response and anti-disease capacity of tilapia while maintaining good growth performance.