The evaluation of growth performance, blood health, oxidative status and immune-related gene expression in Nile tilapia (Oreochromis niloticus) fed dietary nanoselenium spheres produced by lactic acid bacteria

Abstract

The present study was conducted to investigate the effects of lactic acid bacteria-produced nanoselenium spheres (LAB-Se) on the growth performance, blood health, oxidative status and immune-related gene expression in Nile tilapia (initial weight, 14.03 ± 0.04 g). LAB-Se was incorporated into the basal diet at 0.5, 1, 1.5 and 2 mg/kg of diet and fed to the fish for 8 weeks. The results revealed significantly improved final body weights, weight gain, specific growth rates and feed efficiency ratios in fish fed varying levels of LAB-Se (quadratic, P = 0.002, P = 0.002, P = 0.002, and P = 0.04, respectively). The blood haematology and biochemistry parameters of the fish fed varying levels of LAB-Se showed normal values with nonsignificant (P > 0.05) differences, indicating the non-toxic effect of LAB-Se. Additionally, dietary LAB-Se had significant influences on blood total protein and lysozyme and phagocytic activities in tilapia in a dose-dependent manner (quadratic, P = 0.04, P = 0.02, and P = 0.001, respectively). Dietary LAB-Se significantly increased SOD and CAT enzyme activities and decreased MDA levels (quadratic, P = 0.001, P = 0.03, and P = 0.007, respectively); GPX was not significantly affected by LAB-Se inclusion the diets (P > 0.05). Liver and spleen TNF-α expression was significantly upregulated in the fish fed LAB-Se (quadratic, P = 0.007 and P = 0.009, respectively). The expression of liver IL-1β was also upregulated significantly in the fish fed LAB-Se (quadratic, P = 0.005), while spleen IL-1β was not significantly affected by LAB-Se (P > 0.05). Thus, LAB-Se at 1 to 2 mg/kg can be effectively supplemented in tilapia diets to improve growth, oxidative status and immune-related gene expression.