Heat stress is a growing welfare crisis in commercial poultry production as climate change increases summer temperatures, causing suffering, reduced production, and mass mortality.
Broiler chickens bred for rapid growth have elevated metabolic rates that generate substantial body heat. Combined with their dense feathering and inability to sweat, they are highly susceptible to heat stress. Commercial poultry houses with poor ventilation create lethal conditions during heat waves. Affected birds pant rapidly, spread their wings, drink excessively, eat less, and ultimately collapse and die. Heat stress causes significant suffering including physiological changes including elevated cortisol, oxidative stress, and immune suppression in surviving birds. Adaptations including tunnel ventilation, evaporative cooling, shade, and heat-tolerant genetics reduce risk but require investment. Climate change projections suggest heat stress events will become more frequent and severe.