Impact of dietary selenium supplementation on growth performance, bioaccumulation, antioxidant capacity, and gene expression in GIFT strain of Nile Tilapia (Oreochromis niloticus)

The effects of dietary selenium (Se) supplementation on growth performance and antioxidant capacity in GIFT (Genetically Improved Farmed Tilapia) strain of Nile Tilapia (Oreochromis niloticus) are of significant interest due to the potential impact on aquaculture practices and the nutritional quality of fish. Se is an essential micronutrient known for its role in antioxidant defence systems, overall growth and development. A 60-day feeding trial was conducted to study the impact of dietary supplementation with Se on the growth performance, feed efficiency, proximate composition, bioaccumulation in the liver and muscle tissues, antioxidant capacity, and blood biochemistry of GIFT. In a practical diet, sodium selenite (Na₂SeO₃) was added at 0, 0.25, 0.5, 1.0, 1.5, or 2.0 mg Se/kg. Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the Se levels. The ranges of concentrations of Se in feeds were 0.79, 1.05, 1.30, 1.80, 2.25, or 2.80 mg/kg diet. A significant difference in growth was observed at p < 0.001 across the 0.79, 1.05, 1.30, 1.80, 2.25, and 2.80 mg Se/kg diet treatments after 8 weeks. At different dietary Se concentrations, fish liver and muscle Se levels, expression of fish growth gene and antioxidant genes, corresponding enzymes like catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) and the activities of protease, amylase, and lipase in the liver and intestine were significantly different between treatments and were high in fish fed with 1.8 mg Se/kg diet. Similarly, the fish given the 1.8 mg Se/kg diet exhibited a significant increase in the levels of haemoglobin, leucocytes, erythrocyte count, and hematocrit value while lowering the cholesterol level. On Contrary, the proximate analysis did not show any significant difference. Overall, the dietary concentration of 1.8 mg Se/kg diet resulted in the best performance of juvenile GIFT and is recommended if sodium selenite is to be used as the supplementation source.