A Comparison of the Beneficial Effects of Inorganic, Organic, and Elemental Nano-selenium on Nile Tilapia: Growth, Immunity, Oxidative Status, Gut Morphology, and Immune Gene Expression

This study investigates the effects of different sources of selenium (inorganic (SSE), organic (OSE), and elemental nano-selenium (NSE)) on the performance of Nile tilapia (Oreochromis niloticus). In total, 204 Nile tilapia fingerlings were randomly divided into 4 equal groups fed 1 of 4 diets: a control (adding no selenium) and 3 diets as selenium sources (1 mg/kg diet), After a 65-day feeding trial, the growth performance parameters of Nile tilapia were significantly enhanced by dietary selenium supplementation (P < 0.05), with the highest values recorded in the OSE- and NSE-supplemented groups. The selenium-supplemented groups had the highest packed-cell volume, hemoglobin, and red blood cell levels, with the highest values seen in the NSE-supplemented group (P < 0.05). Innate immune-related enzymes and immunoglobulin levels were significantly enhanced with selenium supplementation (P < 0.05); the NSE group demonstrated the highest significant levels of these enzyme activities (P < 0.05). In all selenium-supplemented groups, malondialdehyde levels were significantly and equally reduced (P < 0.05) compared with levels in the control. Bactericidal activity was only enhanced in the NSE group (P < 0.05) compared with other treatments. The expression of TNF-α and IL-Iβ genes was significantly upregulated in selenium-supplemented groups, with the highest expression in the OSE and NSE groups (P < 0.05). These findings support the importance of incorporating selenium in the diet of Nile tilapia. Furthermore, elementary nano-selenium is more effective than inorganic or organic selenium supplementation at improving Nile tilapia growth performance and overall health.