Heat stress is a major and growing welfare challenge in commercial poultry production as climate change increases ambient temperatures, with birds' limited thermoregulatory capacity making them particularly vulnerable.
Poultry experiencing acute heat stress show behavioral signs of thermal distress — wing spreading, panting, reduced activity, and prostration. Severe heat stress causes death through cardiovascular failure and cellular protein denaturation — a process involving significant physiological distress before death. Power outage mortality events in commercial broiler houses, where tens of thousands of birds can die in hours without ventilation during hot weather, represent acute mass welfare disasters. The welfare vulnerability of commercial poultry to heat stress is compounded by selective breeding for fast growth, which reduces heat tolerance, and by climate change trends that increase the frequency of extreme heat events. Emergency planning for power outages and appropriate backup systems are welfare necessities, not options.