Controlled Atmosphere Killing (CAK) systems render poultry unconscious before shackling, eliminating shackling and electrical stunning of conscious birds. Welfare evidence supports wider adoption.
Controlled atmosphere killing represents a significant welfare improvement over conventional electrical stunning for commercial poultry slaughter, primarily because it eliminates the shackling of conscious birds — a process that causes acute pain from joint stress and disorientation. The welfare evidence for CAK is strong enough that it has been adopted as a goal by welfare certification schemes and major poultry buyers. The primary welfare debate within CAK concerns which gas mixtures are most humane: CO2 systems cause aversion and distress during initial exposure, while argon or low-oxygen systems may induce unconsciousness more gently but are more complex to implement. The direction of welfare progress is clear — elimination of conscious shackling should be considered a minimum standard — but ongoing research refines the optimal gas mixture and exposure protocols.