Dietary zinc potentiates thermal tolerance and cellular stress protection of Pangasius hypophthalmus reared under lead and thermal stress

摘要

Zinc micronutrient is the second most abundant trace element in the animal body, as it could not be stored in the body; hence, regular dietary zinc is required for animals. With this backdrops a 60 days feeding trial was conducted to study the effect of dietary zinc on the thermal tolerance and cellular metabolic stress of Pangasius hypophthalmus reared under Pb (1/21th of LC50, 4 ppm) and elevated temperature (34 degrees C). Three isocaloric and isonitrogenous diets with Zn-0, 10 and 20 mg/kg were prepared. Two hundred seventy-three fish were randomly distributed into seven treatments in triplicate in completely randomized forms. Dietary zinc supplementation had remarkable (p & .01) changes on thermal tolerance of P.hypophthalmus viz. CTmin (critical temperature minima) and LTmin (lethal temperature minima), CTmax (critical temperature maxima) and LTmax (lethal temperature maxima). The positive correlations were also observed between CTmin and LTmin (Y = -0.707 + 6.59x, R-2, 0.875) and CTmax and LTmax (Y = -0.923 + 2.45x, R-2, 0.960). The oxidative stress (catalase, superoxide dismutase and glutathione-s-transferase) and lipid peroxidation were significantly reduced and neurotransmitter enzyme (AChE) was significantly enhanced with zinc supplementation at the end of the thermal tolerance. The present study concluded that thermal tolerance of P.hypophthalmus enhanced by zinc supplementation through CTmax LTmax and CTmin LTmin and also by strengthening the antioxidative status along with neurotransmitter enzymes.