Effects of selenium yeast on growth performance, body composition, digestive enzyme activity, antioxidant capacity, and lipid metabolism in juvenile tilapia (Oreochromis niloticus)

This study explored the impact of selenium yeast on the growth performance, body composition, digestive enzyme activity, antioxidant capacity, and lipid metabolism of juvenile GIFT tilapia ( Oreochromis niloticus ). The study involved juvenile tilapia with an initial average weight of 16.17 ± 0.65 g, which were fed five different diets containing varying concentrations of selenium yeast (0 g/kg as the control group, and treatment groups receiving 0.1 g/kg, 0.2 g/kg, 0.3 g/kg, 0.4 g/kg, and 0.5 g/kg) over a period of 60 days. The measured dietary selenium concentrations were 0.05 ± 0.01 mg/kg, 0.26 ± 0.01 mg/kg, 0.44 ± 0.01 mg/kg, 0.64 ± 0.02 mg/kg, 0.87 ± 0.03 mg/kg, and 1.03 ± 0.03 mg/kg, respectively. The results indicated that dietary supplementation with selenium significantly enhanced the final body weight, weight gain rate, and specific growth rate compared to the control group ( p < 0.05). Additionally, the hepatosomatic index, viscerosomatic index, and feed conversion ratio were significantly reduced ( p < 0.05). Whole-body crude protein and selenium contents were significantly increased ( p < 0.05) in all selenium-treated groups compared to the control. Moreover, the activities of trypsin, lipase, and α-amylase in the intestine were significantly enhanced by selenium supplementation ( p < 0.05). At the molecular level, dietary selenium significantly upregulated the expression of catalase, glutathione peroxidase, and glutathione S-transferase in the liver and intestine ( p < 0.05). Additionally, it significantly enhanced the expression of acetyl-CoA carboxylase alpha, carnitine palmitoyltransferase, fatty acid synthase, lipoprotein lipase, phosphoenolpyruvate carboxykinase, peroxisome proliferator-activated receptor alpha, beta, and gamma, as well as sterol regulatory element-binding protein 1 in the liver ( p < 0.05). In summary, the inclusion of selenium in the diet markedly improved growth performance, digestive enzyme function, serum biochemical profiles, and the expression of genes involved in antioxidant defense systems, along with those regulating glucose and lipid metabolism in juvenile GIFT tilapia. Through quadratic polynomial regression analysis, the ideal dietary supplementation level of selenium for juvenile GIFT tilapia was estimated to range between 0.76 and 0.79 mg/kg. • Selenium yeast can significantly enhance the growth performance of juvenile GIFT tilapia. • Selenium yeast can significantly enhance the digestive enzyme activities of juvenile GIFT tilapia. • Selenium yeast can significantly enhance the antioxidant capacity of juvenile GIFT tilapia. • Selenium yeast has a positive impact on lipid metabolism of juvenile GIFT tilapia.