Supplementation of microbial levan in the diet of Cyprinus carpio fry (Linnaeus, 1758) exposed to sublethal toxicity of fipronil: effect on growth and metabolic responses

Abstract

A 60 - day feeding trial was conducted to study the effect of dietary microbial levan on growth performance and metabolic responses of Cyprinus carpio fry exposed to sublethal dose (1/10th LC50) of fipronil [(±) - 5 - amino - 1 - (2,6 - dichloro - a,a,a - trifluorop - tolyl) - 4 - trifluoromethylsulfinylpyrazole - 3 - carbonitrile]. Two hundred and twenty five fry were randomly distributed in five treatments in triplicates. Four purified diets were prepared with graded levels of microbial levan. Five different treatment groups were levan control L0P0 (basal feed ? 0 % levan without exposure to pesticide); pesticide control L0P1 (basal feed ? 0 % levan with exposure to pesticide); L0.25P1 (basal feed ? 0.25 % levan with exposure to pesticide); L0.50P1 (basal feed ? 0.50 % levan with exposure to pesticide); and L0.75P1 (basal feed ? 0.75 % levan with exposure to pesticide). Weight gain% and specific growth rate were significantly higher (p\ 0.05) in levan fed groups compared to their non - levan fed counterpart. Highest (p\ 0.05) content of ascorbic acid in muscle, liver and brain tissues was observed with higher level of dietary levan. Glucose - 6 - phosphate dehydrogenase activity decreased with the increasing level of dietary levan in the liver and muscle. Aspartate aminotransferase activity exhibited a second order polynomial relationship with the dietary levan, both in liver (Y = - 1.001x2 ? 5.366x ? 5.812, r2 = 0.887) and muscle (Y = - 0.566x2 ? 2.833x ? 6.506, r2 = 0.858) while alanine aminotransferase activity showed third order polynomial relationship both in liver (Y = 1.195x3 - 12.30x2 ? 35.23x ? 9.874, r2 = 0.879) and muscle (Y = 0.527x3 - 8.429x2 ? 31.80x ? 8.718, r2 = 0.990). Highest (p\ 0.05) superoxide dismutase activity in gill was observed in the group fed with 0.75 % levan supplemented diet. Overall results indicated that dietary microbial levan at 0.75 % in C. carpio fry ameliorated the negative effects of fipronil and augmented the growth.