CO2 stunning, the most common pig stunning method in Europe, causes significant distress before insensibility and is under increasing welfare scrutiny.
Carbon dioxide is an aversive gas that causes burning of the respiratory mucosa before inducing unconsciousness. Pigs exposed to CO2 show escape behaviours, hyperventilation, and vocalisation for up to 30 seconds before losing consciousness. This period of distress affects billions of pigs annually across the EU. The existence of less aversive alternatives including nitrogen and argon-based gases makes the continued use of CO2 difficult to justify on welfare grounds.