Chicken Slaughter: The Welfare Case for Controlled Atmosphere Systems

Controlled atmosphere killing (CAK) eliminates the live-shackling and waterbath stunning process, representing the most significant welfare advance available for broiler chicken slaughter.

Key Facts

Live-shackling of broilers causes wing fractures in 0.2-1.5% of birds and extreme distress in all birds
Controlled atmosphere stunning using argon or nitrogen produces unconsciousness before any handling
CAK systems require birds to remain in transport containers until death — eliminating catching, shackling and stunning welfare harms
Welbeck Farm, McDonald's UK and M&S require CAK in their UK broiler supply chains
The capital cost of CAK conversion is approximately £1-3M for a typical UK processing plant

Welfare Considerations

Controlled atmosphere killing eliminates the most welfare-costly stages of the conventional poultry slaughter process. Live-shackling — inverting conscious, distressed birds on a moving line before their heads enter a water bath — is replaced by stunning birds to death in their transport modules using inert gas. Birds experience no handling, no inversion, no pre-stun shock, and no pre-stun consciousness during killing. The welfare improvement for each of the 1+ billion UK chickens killed annually would be transformative. The barrier is capital cost and regulatory momentum — addressing either through market demand or regulatory requirement would unlock adoption.

What You Can Do

Choose chicken from supermarkets and fast food chains that require CAK in their supply chains
Ask your favourite chicken brands whether they use or require CAK in their processing contracts
Support CIWF campaigns requiring CAK as a standard welfare requirement for all certified chicken production
Advocate for the UK FSA to set a regulatory transition timeline for CAK adoption in broiler processing
Engage with the capital cost argument constructively — regulatory certainty reduces transition risk and enables investment