Farmed Pig Slaughter Carbon Dioxide Stunning Welfare

Carbon dioxide gas stunning used in most commercial pig slaughter causes a period of distressing breathlessness before unconsciousness, making it one of the more contested practices in animal welfare science and policy.

Key Facts

CO2 stunning is used in the majority of large commercial pig slaughterhouses because it enables group processing
Pigs exposed to high-concentration CO2 show aversion responses including retreat, vocalization, and hyperventilation
CO2 causes unconsciousness through aversive asphyxiation rather than analgesia followed by unconsciousness
Argon and nitrogen gas mixtures cause unconsciousness with less aversion but are less widely adopted commercially
Research by the UK Farm Animal Welfare Council identified CO2 stunning as causing significant welfare harm
Electrical stunning methods avoid CO2 aversion but require individual animal handling increasing stress for some pigs
The welfare window between gas exposure and unconsciousness is estimated at 30 to 60 seconds of aversive experience

Welfare Considerations

Carbon dioxide stunning represents a difficult welfare tradeoff in commercial pig slaughter: it enables efficient group processing that reduces some pre-slaughter handling stress, but achieves unconsciousness through a mechanism that involves a period of respiratory distress that pigs find aversive and attempt to escape. The scientific evidence for CO2 aversion in pigs is robust, and the 30-60 second window of distress before unconsciousness occurs represents a real welfare cost incurred by each of the hundreds of millions of pigs slaughtered using this method annually. Alternative gas mixtures using argon or nitrogen cause unconsciousness with substantially less aversion but face barriers of cost and adoption inertia. The development and commercialization of low-aversion stunning alternatives represents one of the most impactful welfare opportunities in the slaughter sector and merits strong industry and regulatory attention.

What You Can Do

Support organizations advocating for transition away from CO2 stunning toward lower-aversion alternatives
Ask pork retailers and food companies about their slaughter method requirements and welfare standards
Advocate for regulatory requirements for aversion testing of stunning methods and transition timelines
Support research into the practical implementation of argon and nitrogen gas stunning at commercial scale
Reduce pork consumption or choose plant-based alternatives to reduce the number of pigs experiencing this process
Learn about slaughter welfare science from organizations like Compassion in World Farming