CO2 gas stunning of pigs before slaughter causes significant aversion and distress. Developing and implementing more humane alternatives is an active area of welfare science and industry reform.
CO2 pig stunning represents one of the clearest cases where a welfare-inferior method remains dominant due to economics rather than lack of alternatives. The aversive experience of CO2 exposure - panic, choking sensation, and distress before unconsciousness - causes suffering to billions of pigs annually. This is not a marginal or uncertain welfare impact: the evidence of CO2 aversion is robust and the subjective experience is consistently described by researchers as one of the most aversive aspects of commercial pig slaughter. Inert gas alternatives exist, have been implemented at commercial scale, and demonstrate that high throughput pig slaughter without CO2-induced distress is achievable. The barrier is cost, not technology.