Controlled atmosphere stunning (CAS) using gas is increasingly used in poultry slaughter. Welfare outcomes depend critically on gas composition and exposure.
Gas stunning welfare is not equivalent across systems - the common assumption that any CAS system is higher welfare than electrical stunning is incorrect. High CO2 concentration systems cause significant aversive experience before unconsciousness. Advocating for the use of inert gas systems, and against aversive CO2 systems, represents meaningful poultry welfare improvement.