Mass culling during disease outbreaks including avian influenza causes the deaths of hundreds of millions of birds annually using methods that cause significant welfare harm.
Ventilation shutdown with heat causes birds to die slowly from hyperthermia over hours — the welfare assessment is unambiguous and severe. The scale of culling — hundreds of millions of birds — makes the welfare impact of method choice enormous. CO2 or nitrogen gas culling achieves death faster and with less suffering but requires equipment and planning. Vaccination programmes could prevent culling needs but have faced regulatory and trade barriers. Improving culling method welfare standards is a high-priority intervention given current outbreak frequencies.