Exogenous papain supplementation: impacts on growth, digestibility, digestive enzyme activities and oxidative stress in Labeo rohita fingerlings

This study was conducted to evaluate the effects of varying levels of dietary exogenous papain on the growth performance, survival rate, nutrient utilization, protein digestibility, digestive enzyme activity, and oxidative stress response in Labeo rohita fingerlings. A control diet was formulated using rice bran, groundnut oil cake, wheat flour, and a vitamin-mineral mixture. Experimental diets were prepared by supplementing the control diet with different levels of papain enzyme powder: T0 (0% papain, control), T1 (1.0%), T2 (2.0%), T3 (3.0%), T4 (4.0%), and T5 (5.0%). The diets were fed to the fish for 60 days. Results indicated that weight gain, weight gain percentage, daily growth rate (DGR), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), and apparent protein digestibility (APD) significantly improved (P < 0.05) with the inclusion of up to 2% papain in the diet. Throughout the experiment, a 100% survival rate was observed in all groups except T4. Significant differences (P < 0.05) were also noted in PER, protein absorption ratio (PAR), and digestive enzyme activities (lipase and protease) among the treatments. The highest intestinal protease and lipase activities were observed in fish fed the diet supplemented with 2% papain. Additionally, liver antioxidant enzyme activities, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), were significantly enhanced with up to 2% papain inclusion in the diet. Therefore, a 2% inclusion of papain enzyme in the diet is recommended to optimize growth performance, protein digestibility, digestive enzyme activities, and oxidative stress response in Labeo rohita fingerlings.