Synergistic Effects of Dietary Vitamin C, E and Selenomethionine on Growth Performance, Tissue Mercury Content and Oxidative Biomarkers of Juvenile Olive Flounder, Paralichthys olivaceus (Temminck & Schlegel) Toxified with the High Dietary Methylmercury

A 10-week feeding trial was conducted to evaluate the tissue level synergistic effects of dietary vitamin C, E and selenomethionine (SeMet) on dietary methylmercury (MeHg) toxicity in juvenile olive flounder, Paralichthys olivaceus. Eight semi-purified diets were formulated to contain two different vitamin C levels as L-ascorbyl-2-monophosphate (400 and 800 mg AMP/kg diet), two vitamin E levels as DL-α-tocopheryl acetate (100 and 200 mg TA/kg diet) and two selenium (Se) levels as selenomethionine (2 and 4 mg SeMet/kgdiet) on the constant mercury (Hg) level (20 mg MeHg/kgdiet). Eight experimental diets, in a 2×2×2 factorial design (C₄₀₀E₁₀₀Se₂, C₄₀₀E₁₀₀Se₄, C400E200Se₂, C₄₀₀E₂₀₀Se₄, C₈₀₀E₁₀₀Se₂, C₈₀₀E₁₀₀Se₄, C₈₀₀E₂₀₀Se₂ and C₈₀₀E₂₀₀Se₄) were fed to triplicate group of fishes averaging 3.12±0.04g (mean±SD) in the semi-recirculation system. After 10 weeks of feeding trial, weight gain (WG) offish fed diets containing C₄₀₀E₂₀₀Se₄, C₈₀₀E₁₀₀Se₂ and C₈₀₀E₂₀₀Se₂ were significantly higher than those of fish fed diets containing C₄₀₀E₁₀₀Se₂ and C₄₀₀E₁₀₀Se₄ (P<0.05). Feed efficiency (FE), specific growth rate (SGR), protein efficiency ratio (PER) showed a similar trend as WG. The most significant depleting trend of mercury accumulation was found in kidney tissue. Tissue oxidative biomarkers like superoxide dismutase (SOD) and thiobarbituric acid reactive substances (TBARS) in liver and kidney tissues improved up to higher levels of vitamin C, E and Se. Therefore, these findings indicated that the best combinations of dietary antioxidant levels could be C₄₀₀E₂₀₀Se₄ or C₈₀₀E₂₀₀Se₂ diet based on WG by analysis of variance (ANOVA) test in terms of reducing tissue MeHg content in juvenile olive flounder.