Effects of dietary micelle silymarin on the growth performance, feed utilization and health of olive flounder (Paralichthys olivaceus)

Silymarin is phytochemical extracted from milk thistle ( Silybum marianum ). It has been used as a natural hepatoprotector having antioxidant and detoxicant capacities. Micelle form of silymarin is one of the methods to increase its solubility and absorptivity in the intestine. Therefore, this study was performed to estimate the effects of dietary micelle silymarin on olive flounder ( Paralichthys olivaceus ). Experimental diets were prepared by adding dietary micelle silymarin by 0.025, 0.05, 0.1, 0.2 and 0.4% and regular silymarin by 0.1 and 0.2% to a Con diet (designated as M0025, M005, M01, M02, M04, S01 and S02, respectively). After the feeding trial for 70 days, dietary micelle silymarin significantly enhanced growth performance and feed intake of olive flounder. Innate immune responses such as lysozyme, anti-protease, myeloperoxidase and total immunoglobulin were significantly improved by micelle silymarin. Micelle silymarin groups were shown significantly higher antioxidant capacities as superoxide dismutase and glutathione peroxidase, and lower lipid peroxidation as malondialdehyde. Intestine and liver tissues were more positively developed by micelle silymarin. These results indicate that dietary micelle silymarin can enhance the growth performance, feed utilization, innate immune response, antioxidant capacity and histological development of olive flounder. In conclusion, the optimal supplementation level of micelle silymarin is likely to be 0.05–0.1% in olive flounder feed. Compared to regular form, dietary micelle silymarin showed similar or higher effects on olive flounder even at low supplementation levels. Therefore, dietary micelle silymarin is expected to be more effective and economical supplement for olive flounder than regular silymarin.