The method used to slaughter billions of chickens annually has major welfare implications, and the transition from electrical water bath stunning to controlled atmosphere killing represents a significant welfare improvement.
Poultry slaughter welfare affects more individual animals than almost any other welfare intervention because of the sheer scale: billions of birds per year in major producing countries. The switch from water bath electrical stunning to controlled atmosphere systems represents one of the highest-impact welfare improvements available in the food system. Water bath stunning requires live birds to be handled, shackled upside-down in pain-inducing positions, and dragged through the stun system — a process causing welfare costs before any stunning occurs. Controlled atmosphere systems allow birds to be stunned in their transport modules without live handling, but the choice of gas matters: high CO2 causes aversion and distress before loss of consciousness; inert gas systems cause more welfare-positive hypnotic induction. Industry transition is driven by corporate commitments and consumer pressure, with cost being the primary barrier to faster adoption.