The use of carbon dioxide for pig stunning at slaughter causes significant suffering during induction, and welfare-friendly alternatives are being developed and adopted.
CO2 stunning represents one of the most significant unresolved animal welfare problems in livestock slaughter. The period between exposure and unconsciousness involves an aversive experience as the gas causes respiratory distress and air hunger. Research using pigs' own choices in preference tests demonstrates unambiguously that they find CO2 exposure highly aversive. Noble gas alternatives including argon and nitrogen mixtures cause unconsciousness without apparent aversion. The barrier to adoption is primarily economic - CO2 is cheaper than argon. Welfare certification schemes and consumer pressure represent the main routes to accelerating transition to less aversive stunning methods.