Dietary Nano-selenium supplementation improves growth performance of bullfrog (Lithobates catesbeiana): Involvement of oxidative stress and inflammatory response in liver and intestine

This investigation aimed to examine the impact of nano-selenium as a functional feed supplement on bullfrogs. The experiment selected 630 healthy bullfrogs with the same initial weight (24.25 ± 0.02 g) from the same batch, randomly divided into 3 groups with three replicates each. Three different selenium containing diets (CON, N0.4, N0.8) were set based on the basic diet (control group) and supplemented with different levels of nano-selenium (0, 0.4, 0.8 mg/kg) for an 8-week continuous feeding experiment. The experimental results showed that dietary nano-selenium supplementation significantly improved average weight gain rate, total weight gain rate and the survival rate of the bullfrog (P < 0.05). Supplementation of nano-selenium effectively improved intestinal structure and enhanced digestive enzyme activity, thereby facilitating the absorption of nutrients. In addition, nano-selenium supplementation alleviated liver impairment in bullfrogs due to dietary challenges, as evidenced by more structurally intact hepatocytes, significantly reduced cell vacuolization, and GOT and GPT activity in the nano-selenium group. Moreover, the serum content of acid phosphatase (ACP) and alkaline phosphatase (AKP) were significantly increased followed nano-selenium addition (P < 0.05), indicating the enhanced host innate immune capacity. Dietary nano-selenium intake boosted the antioxidant capacity and relieved inflammatory response of liver and intestine tissues at enzymatic and transcriptional level. In conclusion, nano-selenium can effectively improve the health condition of bullfrogs, combined with the actual production to evaluate the optimal additive amount of 0.4 mg/Kg.