also reported that dietary RSV supplementation (200, 400, and 600 mg/kg) linearly increased BWG and decreased FCR of blackboned chickens during heat stress. The results of previous researches suggested that RSV supplementation could improve gut integrity and barrier function (as a key factor for nutrient utilization and adsorption) through stimulating the growth of useful bacteria and inhibiting the colonization of pathogens and regulating the immune system, and these beneficial outcomes together may eventually contribute to the improved growth performance (Ahmed et al., 2013;