Farmed Pig Slaughter Welfare: CO2 and Alternatives

CO2 stunning of pigs is the dominant commercial slaughter method but causes aversion and distress before insensibility. Alternative stunning methods offer welfare improvements but face practical barriers to adoption.

Key Facts

Over 90% of UK pigs are stunned with high-concentration CO2 before slaughter
Pigs exposed to CO2 show avoidance behaviour, hyperventilation, and vocalisations before losing consciousness
CO2 causes respiratory irritation and acidification of airway mucosa before inducing insensibility, creating a distressing experience
Alternative atmospheric gas mixtures including nitrogen and argon-based mixes can induce insensibility without the aversive effects of CO2
Low atmospheric pressure stunning (LAPS) has been developed as another CO2 alternative but is not yet commercially adopted at scale
The UK Farm Animal Welfare Committee has recommended transition away from CO2 stunning toward less aversive alternatives

Welfare Considerations

CO2 stunning represents one of the most significant unresolved welfare issues in commercial pig slaughter. The aversive nature of CO2 exposure is well-documented: pigs exposed to high-concentration CO2 attempt to escape, vocalise, and show breath-holding behaviour before losing consciousness - all indicators of aversive distress. The duration of this aversive period before insensibility is approximately 20-30 seconds, multiplied by the tens of millions of pigs stunned annually, represents an enormous aggregate welfare burden. Alternative gas mixes (nitrogen, argon, or low-CO2 mixes) that induce insensibility before or concurrent with CO2 exposure reduce or eliminate this aversive period. Barriers to adoption include capital costs of replacing existing stunning systems and gas availability. The welfare case for transition is scientifically clear; the mechanism for achieving it is regulatory and economic.

What You Can Do

Support campaigns for mandatory transition from CO2 to less aversive stunning methods in pig slaughter
Choose pork from producers that have adopted non-CO2 stunning alternatives where available
Advocate for government timeline requirements for CO2 stunning phase-out
Support research into commercially viable CO2 alternatives including nitrogen and argon systems
Contact retailers asking them to incentivise supplier adoption of welfare-positive slaughter methods
Reduce pork consumption or eliminate it as a response to the scale of CO2 stunning welfare harm