Poultry slaughter involves more individual animals than any other sector of animal agriculture, and the methods used to render birds unconscious before killing are a major welfare focus.
Poultry slaughter welfare is numerically the most significant welfare issue in commercial animal agriculture — the sheer number of birds processed makes even small percentage improvements in stunning effectiveness enormous in welfare terms. The dominant waterbath electrical stunning system has known failure modes: birds that raise their heads miss the stun and remain conscious through subsequent neck cutting. Controlled atmosphere stunning (CAS) using inert gas mixtures eliminates this failure mode by rendering all birds unconscious before any handling, but requires capital investment and produces different carcass quality characteristics. High welfare CAS with nitrogen or argon mixtures is widely considered the gold standard; CO2 systems are effective but birds show distress during the CO2 exposure phase before losing consciousness. Consumer and retailer pressure has driven significant uptake of CAS systems in Europe and increasingly in North America.