Abstract This study was performed to evaluate the effects of adding methionine supplements to low-protein diets and subsequent re-feeding with a normal diet on the productive performance, slaughter parameters, leukocyte profiles and antibody response in broiler chickens reared under heat stress conditions. During the whole experimental period (6–49 days), the birds were raised in battery cages located in high ambient temperature in an open- sided housing system. A total of 360 6-day-old male chickens were divided into six ...