Synergistic effects of dietary vitamin E and selenomethionine on growth performance and tissue methylmercury accumulation on mercury-induced toxicity in juvenile olive flounder, Paralichthys olivaceus (Temminck et Schlegel)

Abstract

An 8-week feeding trial was conducted to evaluate the synergistic effects of dietary vitamin E and selenomethionine (SeMet) on induced methylmercury (MeHg) toxicity in juvenile olive flounder Paralichthys olivaceus. Nine semi-purified diets were formulated to contain three different vitamin E levels as DL-α-tocopheryl acetate (0, 100 and 200 mg TAkg−1 diet) and three different selenium (Se) levels (0, 2 and 4 SeMet mg kg−1 diet) on the constant mercury toxicity level (20 mg MeHgkg−1 diet). Nine experimental diets, in a 32 factorial design (E0Se0, E0Se2, E0Se4, E100Se0, E100Se2, E100Se4, E200Se0, E200Se2 and E200Se4), were fed to triplicate groups of fish averaging 2.3 ± 0.04 g (mean ± SD) in the semi-recirculation system. After 8 weeks of feeding trial, vitamin E and Se showed significant effects on weight gain (WG) of fish (P < 0.05). We found that there was a clear trend of increasing WG with elevating vitamin E and Se levels in the diets. Feed efficiency (FE), specific growth rate (SGR), protein efficiency ratio (PER) and survivability exhibited a similar trend with WG. Both antioxidants had significant interaction effects on FE and PER (P < 0.05). Methylmercury concentrations in fish muscle, liver and kidney decreases in a dose-dependent manner as dietary vitamin E and Se levels increase. Interestingly, the most significant interactive effects of vitamin E and Se were found in liver tissue for depleting Hg concentrations (P < 0.05). These findings suggest that dietary vitamin E more than 100 mg TA kg−1 diet with 2 or 4 mg SeMet kg−1-supplemented diets could have synergistic effects on growth and liver mercury bioaccumulation on MeHg-induced toxicity in juvenile olive flounder.