Poultry Heat Mortality: A Worsening Climate Crisis

Heat-related mortality in commercial poultry flocks represents one of the most severe acute welfare events in animal agriculture, causing millions of deaths annually and set to worsen significantly as climate change drives more frequent and intense heat events.

Key Facts

Heat stress kills tens of millions of poultry birds annually in the US alone, with individual heat events causing flock mortalities of 10-100% in severe cases
Broiler chickens selectively bred for rapid growth are particularly vulnerable — their high metabolic rate generates additional body heat they cannot dissipate
Poultry lack sweat glands and rely on panting for evaporative cooling — a mechanism that becomes insufficient when temperatures exceed 35°C with high humidity
The 2021 Pacific Northwest heat dome killed an estimated 1 million poultry birds in a single event in Oregon and Washington state
Ventilation failure in enclosed poultry houses — from power outages or equipment malfunction — can cause near-total flock mortality within hours
Birds experiencing heat stress show elevated respiratory rates, prostration, loss of coordination, and seizures before death
Climate projections indicate that regions currently marginal for poultry heat stress will experience routine severe events within decades

Welfare Considerations

Death by heat stress is one of the most distressing acute welfare events experienced by farmed animals. Birds in the final stages of heat stroke experience respiratory distress, disorientation, and loss of neurological control — a progression from discomfort through distress to death that unfolds over hours in severe heat events. The scale of mortality in single events can reach hundreds of thousands of birds in a single house, each experiencing this trajectory. The systemic nature of the problem — driven by the combination of metabolic heat from fast-growing breeds, high stocking densities, and enclosed housing — means that individual heat events are predictable features of the system rather than unforeseeable disasters. Prevention through breed selection, density management, and ventilation investment is straightforward in principle but requires economic pressure to implement.

What You Can Do

Support welfare standards that require adequate ventilation capacity and backup power for poultry housing
Advocate for stocking density limits that reduce heat load in poultry flocks
Choose poultry products from slower-growing breeds with lower metabolic heat output and better heat tolerance
Support climate adaptation funding for poultry farmers to install shade, ventilation improvements, and backup power systems
Advocate for mandatory mortality reporting in poultry operations to quantify the scale of heat-related welfare events
Engage with climate change as a direct animal welfare issue — warming temperatures directly cause animal deaths and suffering