CO2 stunning of pigs is the most common commercial slaughter method but is aversive and causes distress before unconsciousness, with alternatives being developed and adopted.
Pig slaughter welfare is a significant and tractable welfare problem given that approximately 1.3 billion pigs are slaughtered globally each year. The dominant CO2 stunning method is now well-established as causing aversive experiences before unconsciousness, with pigs showing clear distress during exposure. Inert gas alternatives and low atmospheric pressure systems achieve unconsciousness with substantially less apparent distress. The transition to these systems requires investment but represents a meaningful welfare improvement for hundreds of millions of animals annually.