Effects of long-term silymarin oral supplementation on the blood biochemical profile of rainbow trout (Oncorhynchus mykiss)

Silymarin, an extract from milk thistle (Silybum marianum) plant is traditionally used as herbal medicine. The present study was conducted to investigate the clinical effects and possible side effects of silymarin on biochemical blood parameters of rainbow trout (Oncorhynchus mykiss). Fishes were treated with 0 (control), 100, 400, and 800 mg of silymarin per kg of food during 4 weeks. Plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), creatine kinase (CK), glucose, total protein, creatinine, triglyceride, cholesterol, urea, uric acid and liver cellular total antioxidant, and protein content were measured after 7, 14, and 28 days of silymarin treatment. The results showed that oral administration of silymarin in fish significantly reduced plasma glucose and cholesterol levels and relatively increased plasma total protein and globulin concentrations (P < 0.05). Increasing plasma albumin levels indicate the important role of albumin in drug transportation in circulatory system of fish. Silymarin also stabilized cellular membrane structure and regulated the levels of AST, ALT, ALP, CK, and LDH activity. In conclusion, on the basis of these results, oral administration of silymarin up to 400 mg per 1 kg of food has no side effect on blood biochemical and clinical parameters of fishes. However, oral administration of 800 mg/kg- of silymarin caused cytotoxicity and modifications in blood biochemical parameters of fish.