Field Study to Relate Heat Stress Index to Broiler Performance

This study was conducted to determine environmental parameters related to the heat stress of broiler chickens. A total of 50 broiler flocks across 4 regions in Alberta were used to identify factors that contribute to heat stress. A heat stress index was calculated as a function of the deviation of actual from target environmental temperature and bird age. Principal component analysis was performed to determine key characteristics relating heat stress, bird performance, and carcass quality. Key relationships that emerged included an improvement in carcass quality and broiler microclimate with misting. Even when the heat stress index was not severe, misting reduced condemnations at the processing plant and total mortality. In the southern region, high ventilation rates did not reduce heat stress; only misting was effective. When heat stress is low, broilers can be grown at stocking densities >35 kg/m² without compromising carcass quality.