Slaughter welfare for pigs is determined primarily by pre-slaughter handling and stunning method effectiveness, with CO2 stunning being increasingly controversial due to evidence of aversion in pigs.
Slaughter represents the final welfare event for billions of pigs annually. The evidence that CO2 stunning - used for the majority of pigs globally - is aversive is now substantial. Pigs exposed to CO2 show behavioral and physiological signs of distress including rapid respiration, attempts to escape, vocalization, and apparent panic. Pre-slaughter handling adds additional welfare harm when conducted with excessive speed, electrical prodding, and falls from slippery surfaces. The scale of slaughter means even small improvements in stunning and handling methods deliver welfare benefits for millions of animals. Investment in CO2 alternative stunning technologies and improved handling practices is justified both ethically and potentially economically.