CO2 stunning of poultry before slaughter causes aversive breathing difficulty before unconsciousness. Alternative gases and technologies offer more humane pre-slaughter unconsciousness.
Poultry stunning welfare is one of the largest single welfare improvement opportunities in animal agriculture given the scale — billions of chickens are stunned annually with methods causing varying degrees of pre-unconsciousness distress. CO2 stunning causes dyspnea (breathing difficulty) that is demonstrably aversive in animal models — birds showing escape behavior and distress during CO2 exposure. Inert gas stunning with argon or nitrogen causes unconsciousness through oxygen deprivation without the aversive respiratory irritation of CO2. The primary barrier to adoption is cost — CAK systems require significant capital investment. Consumer demand for welfare-certified poultry and retailer commitments to better slaughter standards can create the market conditions for industry investment in higher-welfare stunning.