Farmed Pig CO2 Stunning Welfare: Alternatives to Aversion

CO2 stunning of pigs is widely used but causes distress during gas induction, making it a significant welfare challenge at an unavoidable step in the slaughter process.

Key Facts

The majority of UK pigs are slaughtered using CO2 gas stunning, which renders animals insensible before bleeding
CO2 is aversive to pigs: scientific evidence shows animals will press a bar to avoid CO2 exposure
During induction, pigs show clear signs of distress including increased vocalisation, head movements, and attempts to escape
Alternative gases including argon, nitrogen, and various mixtures cause less aversion in research studies
The EFSA (European Food Safety Authority) has recommended phasing out high-CO2 pig stunning
Technical and cost barriers have slowed transition to lower-aversion alternatives
Some producers have invested in controlled atmosphere systems using argon mixtures with less aversion
Research continues on optimising gas composition and delivery to minimise distress during induction

Welfare Considerations

CO2 pig stunning is the most significant welfare problem in UK pig slaughter that has an available technical solution but has not yet been widely replaced. The scientific evidence that CO2 causes aversive distress during induction is robust and widely accepted; the regulatory response has been slow. Alternative gas mixtures that cause less aversion are commercially available but require capital investment to implement. Consumer and retailer pressure for higher-welfare slaughter certification - specifically requiring low-aversion gas stunning - is the most accessible market lever for accelerating the transition to welfare-improved slaughter methods.

What You Can Do

Support campaigns for mandatory transition away from high-CO2 pig stunning
Choose pork products from producers using lower-aversion gas stunning systems where certified
Ask retailers about the stunning methods used at abattoirs in their pork supply chains
Donate to humane slaughter research organisations developing and validating low-aversion alternatives
Advocate for regulatory requirements for lower-aversion gas stunning in EU and UK pig slaughter regulations