Effects of Dietary Organic Selenium Supplementation on Performance and Antioxidant Enzymes of Broilers under Heat Stress Conditions: A Meta-Analysis

Heat stress is a major cause of growth retardation and one of the most significant stressors that affect poultry, especially in hot parts of the world. This meta-analysis aimed to evaluate the effect of organic selenium supplementation on antioxidant enzymes and the performance of broiler chickens in heat-stress conditions. From 2003 to 2022, the Scopus, PubMed, Web of Science, and Google Scholar databases were searched. A total of 49, 43, 48, 19, and 27 trials were included to evaluate organic Se effects on feed intake (FI), average daily gain (ADG), feed conversion ratio (FCR), superoxide dismutase (SOD), and glutathione peroxidase (GPX) respectively. The use of organic Se supplementation had no significant effect on ADG (SMD=-0.009, 95% CI -0.105 to +0.086, I2=67.28, P=0.85), FI (SMD=-0.092, 95% CI -0.392 to +0.208, I2=58.53, P=0.548) and FCR (SMD=0.003, 95% CI -0.006 to +0.013, I2=62.89, P=0.47) in the pooled standardized mean difference random effect model. A low concentration of GPX was found in the control group (P=0.000, I2=86.32) in comparison to organic Se supplemented broilers. On the other hand, when the random model was applied to GPX studies, there was much heterogeneity. The standard mean differences of SOD were significantly higher (P 0.041, 95 CI 0.000 to +0.006, I2=0.71) in the treatment receiving Se supplementation. In conclusion, this meta-analysis shows that adding organic Se did not significantly affect on performance, but significantly increased the concentration of SOD and GPX in broilers under heat stress.