Billions of pigs are slaughtered for food annually, and high concentration CO2 within controlled atmospheric stunning (CAS) systems is one of the most common methods used to stun pigs unconscious at the time of slaughter. However, a high concentration of CO2 is aversive, and creates severe animal welfare problems for pigs. Numerous alternative stunning methods have been proposed, including inert gases, electrical and mechanical methods, low atmospheric pressure stunning, and nitrogen foam. After reviewing studies of the animal welfare impacts associated with these methods, stunning using the inert gas argon created the least severe welfare problems, with the lowest cost increases for the industry. Accordingly, the industry is recommended to switch to argon using the CAS infrastructure already in place. Although the associated welfare impacts of argon remain significant, and are not acceptable from ethical or animal welfare perspectives, they represent a significant improvement on CO2 stunning. Published study:
http://doi.org/10.3389/fvets.2025.154....