The method used to stun pigs before slaughter profoundly affects their welfare in the final minutes of life, with significant variation in effectiveness and humaneness across the techniques used globally.
Pig slaughter welfare is determined primarily by the experience of the induction to unconsciousness — the interval between entering the stunning system and loss of consciousness. CO2 gas, despite its wide use, is genuinely aversive: pigs show distress behaviours including backing away, vocalising, and headshaking as CO2 concentration rises, and the experience of breathlessness and acidosis before unconsciousness represents real suffering. Electrical stunning is rapid when applied correctly but is highly technique-dependent; incorrect electrode placement or insufficient current duration causes partial stunning that immobilises without inducing unconsciousness. High-welfare stunning systems using inert gas avoid hypercarbia but are more expensive to install. The welfare case for investment in better stunning infrastructure is strong — the cost per pig is minimal relative to the welfare gain. Pre-slaughter welfare — handling, transport, lairage, and stunning — deserves equal attention to on-farm welfare as the endpoint of every farmed pig's life.