Poultry Controlled Atmosphere Stunning Welfare

Controlled atmosphere stunning (CAS) using low-oxygen or CO2 mixtures is increasingly used for poultry slaughter, with welfare implications varying significantly between different gas protocols.

Key Facts

Low-oxygen CAS (nitrogen or argon-based) causes unconsciousness without aversion signs
High-concentration CO2 CAS causes aversion and distress before unconsciousness
Two-phase CO2 systems use low CO2 first to induce unconsciousness then higher concentrations
CAS allows whole-cage or container gassing, reducing handling stress compared to electrical stunning
CAS with argon or nitrogen provides the best welfare outcome of currently available methods

Welfare Considerations

Controlled atmosphere stunning welfare depends critically on the gas used. High-concentration CO2 causes detectable aversion and distress before unconsciousness - birds display escape behaviour and respiratory distress. Low-oxygen protocols using nitrogen or argon, or two-phase CO2 systems that avoid high concentrations during the conscious phase, achieve unconsciousness more humanely. Retailer and certification scheme specifications for gas protocols drive industry adoption of better methods.

What You Can Do

Support poultry certification schemes that specify CAS protocols without aversive CO2
Advocate for phasing out high-concentration CO2 CAS in favour of low-oxygen methods
Choose chicken and turkey products from producers using low-aversion stunning methods