The modulation effects of dietary zinc on reproductive performance and gonadotropins (FSH and LH) expression in threatened Asian catfish, Clarias magur (Hamilton, 1822) broodfish.

Abstract

The availability of zinc has been correlated with reproductive performance. To validate the hypothesis, a 60-day feeding trial was conducted to evaluate the effect of dietary zinc on reproductive performance and gonadotropin gene (FSH and LH) expression in threatened Clarias magur brooder. Four isonitrogenous (35%) and iso-energetic (372.18 ± 1.73 k cal/100 g) diets were prepared with zinc acetate as control (100 mg/kg diet normal requirement), T1 (50 mg/kg diet, low zinc), T2 (200 mg/kg diet, medium zinc) and T3 (300 mg/kg diet, high zinc). The weight gain % and specific growth rate were significantly (p < 0.05) decreased with the increased dietary zinc level. The pituitary mRNA levels of FSH were assessed during the reproductive cycle of female C. magur, and the FSH expression was increased which was significantly (p < 0.05) highest in T1 group. Similarly, LH expression was revealed to be highest. In all treatment groups except T1, GTH expression reduced significantly by increasing zinc inclusion in the diet. GSI and fecundity were lowest during initial sampling and start to increase was observed. The highest GSI and fecundity were recorded in the T1; however, GSI and fecundity significantly (p < 0.05) reduced with increasing the zinc level. Reproductive parameters like spawning fecundity, fertilization rate, hatch-ing rate and larval survival were found to be dose-dependent of zinc. This revealed that 50 mg/kg zinc was optimum for enhanced reproductive performance; therefore, the present study proposed that 50 mg/kg of zinc could be supplemented for flexible enhanced reproductive performance in threatened Asian catfish, C. magur