DIETARY SUPPLEMENTATION OF SILYMARIN ON GROWTH, GLYCOLIPID METABOLISM, AND ANTIOXIDANT ACTIVITY OF MANDARIN FISH (SINIPERCA CHUATSI)

Silymarin was added to commercial feed at ratios of 0, 0.5‰, 2‰, and 3.5‰, designated as groups A0, A0.5, A2, and A3.5, respectively. A total of 360healthy mandarin fish (Siniperca chuatsi) with an average weight of (35±0.69) g were randomly divided into 4 groups, with 3 replicates in each group and 30 per replicate. The fish were fed the experimental diets for 69d. The results showed that: (1) There were no significant changes in weight gain rate, specific growth rate, plumpness, liver to body ratio, and mesenteric fat index in each group of mandarin fish (P>0.05), while the feed coefficient of A2 and A3.5 groups significantly decreased (P<0.05). The survival rate in the treatment group with the addition of silymarin was significantly higher than that in the A0 group, and the A2 group had the highest survival rate (P<0.05). (2) The content of liver and muscle glycogen significantly decreased with the increase of silymarin supplementation (P<0.05). The serum triglyceride concentration of each group with the addition of silymarin significantly decreased, reaching the lowest level in the A3.5 group (P<0.05). As the amount of silymarin added to the feed increased, the concentrations of insulin and glucagon (GCG) in the serum of each group gradually increased, reaching their maximum in the A3.5 group (P<0.05). (3) The H&E pathological sections also observed a decrease in cellular vacuolization, sinus blockage, and alleviation of nuclear translocation in the liver tissue treated with silymarin. The nuclear and cytoplasmic structures, as well as cell boundaries, were more complete and clearer compared to the A0 group. (4) The activities of glucose kinase and phosphoenolpyruvate carboxylase were significantly increased in groups A2 and A3.5 (P<0.05), and the activity of glucose-6-phosphatase (G6P) gradually increased with the increase of silymarin addition (P<0.05), while hexokinase activity significantly decreased in groups A2 and A3.5 (P<0.05). Activities of phosphofructose kinase 1 and pyruvate kinase in groups with silymarin addition were significantly reduced (P<0.05). The total antioxidant capacity of the liver significantly increased with the addition of silymarin levels (P<0.05). (5) After adding silymarin, the expression of the glycogen synthesis related gene gys2 in the liver were significantly reduced, while the levels of gk, pfk1, and g6p in glucose metabolism related genes were significantly reduced (P<0.05). The fas expression of lipid metabolism related genes in group A2 was significantly reduced (P<0.05), and lpl expression levels in A0.5 and A3.5 groups were significantly reduced (P<0.05). Compared with group A0, the level of antioxidant related gene cat expression in the liver increased with the increase of silymarin addition, reaching its maximum in group A3.5 (P<0.05). The gpx expression significantly increased, reaching its maximum in the A0.5 group (P<0.05). In summary, adding silymarin to the feed of mandarin fish can significantly improve its survival rate and feed utilization, regulate its glucose and lipid metabolism, reduce glycogen deposition and lipid accumulation, and enhance its liver antioxidant capacity. Optimal effects were observed with silymarin supplementation levels of 2‰ and 3.5‰.