High-concentration carbon dioxide gas stunning for poultry at slaughter causes aversion and distress before loss of consciousness, and controlled atmosphere killing with different gas mixtures offers welfare improvements.
Gas stunning represents a significant welfare compromise in commercial poultry slaughter. High-concentration CO2, the most widely used method, causes birds to show avoidance behaviour, heightened respiration, and apparent distress during the period between exposure and loss of consciousness. Alternative gas mixtures using argon or nitrogen to cause unconsciousness through oxygen deprivation cause death more gently, without the aversive acidosis response of CO2. The welfare case for transitioning to low-aversion gas methods is strong, and several large producers have made this commitment, but widespread adoption requires industry-wide standards.