Effects of dietary nano-selenium concentration on growth, proximate chemical composition and antioxidant enzymes, and physiological responses to stressors by juvenile Catla catla

Abstract

This study evaluated effects of nano‑selenium (nano-Se) on growth, feed utilization and antioxidant status of Catla catla fed isonitrogenous (26.25% protein) and isolipidic (13.12% lipid) diets formulated to contain nano-Se at 0, 0.75, 1.5 and 2.25 mg/kg (analysed Se 0.32, 1.08, 1.81 and 2.61 mg/kg). There were three tanks (89 × 58 × 61 cm) for each of the four feed treatments, and each tank of 25 fish (initial weight of 6.41 ± 0.02 g) was fed to satiation twice each day for 90 days. After 90 days, growth performance and survival rate were noted and then 9 fish from each replicate were harvested and analysed for body proximate composition, serum biochemistry and antioxidant enzyme activities. The remaining 16 fish from each replicate were subjected to temperature and hypoxia stress (8 fish against each stressor). Orthogonal polynomial contrast analysis revealed dietary nano-Se supplementation significantly improved the growth performance and feed utilization in linear, quadratic trends. Fish fed diet containing 1.08 mg/kg nano-Se showed highest weight gain (28.00 ± 0.84 g) and specific growth rate (1.87 ± 0.01%/day) and lowest FCR (1.07 ± 0.03). However, no significant effect was observed on the feed intake or survival rates of the fish. Furthermore, whole body moisture, crude protein (CP) and ash contents showed significant linear and quadratic trends in response to dietary nano-Se. Before and after stress challenges, significant increase in liver superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase activities (GPx) and decrease in thiobarbituric acid reactive substances (TBARS) were observed in fish fed 1.08 mg/kg nano-Se diets compared with the control group. Before stress, nano-Se supplementation had no effect on the levels of serum glucose (GLU), serum cortisol (CORT) or the survival rate (SR), however, significant elevations in these parameters were observed after stress challenges. Fish fed 1.08 mg/kg nano-Se diet showed significantly lower values of GLU, CORT and SR as compared to the control group after each stress challenge. In conclusion, nano-Se supplementation improved the growth performance, health status and response to stressor in Catla catla. The optimum nano-Se concentration in the diets of C. catla was estimated to be 1.54, 1.60, 1.58 and 1.64 mg/kg on the basis of weight gain percent, FCR, TBARS and GLU, respectively.