الفهرس 
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Abstract
The first study was conducted to 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 hematology and biochemistry parameters of the fish fed varying levels of LAB-Se showed normal values with non significant (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.
In conclusion, the supplementation of LAB-Se at 1 to 2 mg/kg of feed has the potential to increase the growth, health, and immunity of Nile tilapia. Dietary LAB-Se also stimulated the oxidation status of Nile tilapia in a particular way. LAB-Se activated blood immune responsesand TNF-α and IL-1β gene expression, which significantly improves defence against stressors and infectious pathogens in Nile tilapia.
In the second study which conducted to investigate the effects of nano selenium (Nano Se) or/and vitamin E (VE) on growth performance, blood health, intestinal histomorphology, oxidative status and immune related gene expression of Nile tilapia. Nano Se or/and VE at a rate of 0, 1 mg Nano Se /kg, 100 mg VE/kg and 1 mg Nano Se/kg+ 100 mg VE diet and fed to fish for 8 weeks. FBW was significantly (P<0.05) increased in fish fed Nano Se and VE, while fish fed Nano Se or Nano Se and VE diets displayed significantly (P<0.05) higher WG and SGR than the other groups.
The lowest FCR was significantly (P<0.05) detected in fish fed Nano Se and VE, while the highest value was observed in fish VE diet. The intestinal morphometry (villi length and width) of fish fed Nano Se or/and VE reported significantly (P<0.05) the highest values with high number of goblet cells. Blood hematology and biochemistry parameters of fish fed Nano Se or/and VE showed normal values with insignificant differences except for the blood total protein increased in fish fed Nano Se or/and VE (P<0.05). Dietary Nano Se or Nano Se and VE significantly (P<0.05) increased the GPX, SOD, CAT, NBT, lysozyme and phagocytosis values with decreased MDA. Liver and spleen TNF-α and IL-1β expressions were significantly (P<0.05) upregulated in fish fed on Nano Se or Nano Se and VE. Thus, Nano Se or/and VE can be used effectively in tilapia’ diets for improving the growth, intestinal health, blood health, oxidative status and immune related gene expression.