Abstract:
In recent years, the bullfrog (
Rana catesbeiana) farming industry has undergone rapid scaling and intensification. To enhance production efficiency, feed formulations with a high soybean meal ratio have become a mainstream strategy. However, anti-nutritional factors present in soybean meal can easily induce intestinal oxidative stress and inflammatory responses, compromising the immune defense system. This ultimately hinders the healthy and sustainable development of the bullfrog industry. To investigate the effects of different selenium sources on growth performance, serum biochemistry, and intestinal antioxidant and inflammation in under high soybean meal dietary conditions. A total of 840 healthy
R. catesbeiana of the same batch with an initial weight of (24.25±0.02) g were randomly divided into four groups with three replicates in each group. The control (CON) feed, and the experimental feed with the addition of yeast selenium (Y0.8), sodium selenite (S0.8), and nano-selenium (N0.8) at an effective level of 0.8 mg/kg to the control feed, were fed separately for 8 weeks. The results showed that all three selenium sources promoted growth, improved survival rate, and reduced the feed coefficient. Among them, the Y0.8 group exhibited the highest weight gain rate, which was significantly increased by approximately 31.44% compared to the control group. The S0.8 group showed a significant increase of about 21.89%, while the N0.8 group showed an increase of about 10.88%, though not statistically significant. Regarding survival rate, both Y0.8 and S0.8 groups showed improvements without significant differences, whereas the N0.8 group demonstrated a significant increase of about 15.24%. Additionally, the total weight gain rate in the N0.8 group was significantly higher than that in the Y0.8 and S0.8 groups. Compared to the control group, selenium supplementation effectively enhanced digestive enzyme activity and improved intestinal morphology. Meanwhile, GOT and GPT, as well as the levels TC and TG, were reduced in all experimental groups. Furthermore, intestinal antioxidant capacity was significantly enhanced in all selenium-supplemented groups, as evidenced by a significant decrease in malondialdehyde (MDA) content, increased activities of antioxidant enzymes (GSH-Px, SOD, CAT, T-AOC), and upregulation of related gene expressions (
gpx5,
sod,
cat,
gstp). Selenium supplementation also effectively suppressed the expression of pro-inflammatory factors (
il-8,
il-1
β) and promoted the expression of the anti-inflammatory factor
il-10. The study indicates that supplementation with all three selenium sources significantly improves growth performance and mitigates the adverse effects of high soybean meal diets in
R. catesbeiana. Nano-selenium demonstrated overall superior effects compared to selenium yeast and sodium selenite. These findings provide theoretical and experimental support for the application of different selenium sources in
R. catesbeiana feed, offering positive implications for alleviating the negative impacts of high soybean meal diets, improving
R. catesbeiana health in aquaculture, and enhancing economic efficiency.