Fermented rice polishings dietary supplementation sustainably enhanced growth performance, gut morphology, immune response and antioxidant status of Nile tilapia

Fermentation of plant-derived by-products, including rice polishings (RP), is suggested for the sustainability of the aquafeed industry. In this study, fermented rice polishings (FRP) were incorporated into Nile tilapia diets at various levels: 0, 100, 200, 300, and 400 g/kg. Nile tilapia with an average initial weight of 19.25 ± 0.25 g/fish were divided into five groups (triplicates) and fed five test diets (R0, R10, R20, R30, and R40) for 85 days. Dietary FRP substantially increased final body weight, weight gain, specific growth rate, and protein efficiency ratio, but decreased feed conversion ratio compared to the control group (R0). According to regression analysis, dietary FRP at 210 to 230 g/kg leads to optimal growth performance. Fish fed with higher levels of FRP (R20, R30, and R40) showed greater crude lipid content in the carcass compared to R0 and R10. Graded FRP levels considerably enhanced intestinal architexture, particularly at R20 and R30 levels. Fish fed FRP showed a dose-dependent increase in digestive enzyme activity up to 300 g/kg (R30), with the R20 having the greatest activity. Serum lysozyme levels increased significantly across all FRP levels. Serum immunoglobulin activity enhanced considerably in the R20 and R30 groups. R20 had the greatest lysozyme and immunoglobulin activity. Fish given graduated FRP levels had higher levels of total antioxidant capacity, SOD, and CAT compared to R0, with R20 exhibiting the greatest activity. Ultimately, dietary FRP can be added at 210-230 g/kg to enhance the growth performance, productivity, gut shape, digestive enzyme activity, blood health, immunity, and antioxidant response of Nile tilapia.