The method of slaughter has enormous welfare implications for the billions of chickens killed annually. Current practices vary widely in the suffering they cause, and improvements are achievable.
Slaughter method is a critical welfare variable for chickens. Water bath stunning at conventional parameters frequently fails to induce unconsciousness in all birds — the result is that millions of birds have their throats cut while still conscious, experiencing acute pain during the time to loss of consciousness from blood loss. Controlled atmosphere systems that use inert gas (nitrogen or argon) eliminate pre-stun pain entirely and are the gold standard for welfare. High-CO2 systems, while better than water bath, cause aversion responses during induction. The Better Chicken Commitment includes controlled atmosphere killing as a requirement, and many food companies have committed to transitioning. The welfare case for mandatory effective stunning before slaughter is scientifically unambiguous.