In early February, the animal activist group Direct Action Everywhere, posted undercover video footage online of the reaction of pigs to CO₂ stunning. An activist named Raven Deerbrook snuck into the Farmer John pork plant in Los Angeles in October 2022. She placed a miniature video camera in the shaft of the CO₂ stunner. The video definitely showed that some of the pigs were having a bad reaction and were attempting to escape.

I have looked into these chambers many times. I have observed that some pigs have a very mild reaction to controlled atmosphere stunning (CAS) and others go berserk and attempt to escape. Years ago, I visited the Danish Meat Research Institute in Roskilde, Denmark. I watched Danish pigs in a CO₂ chamber in their research lab. These pigs had a very calm reaction. In this system, it was easy to see the pigs walking around in 90% CO₂. They backed up a little bit and then fell over and lost the ability to stand. After they fell over and lost posture, they became unconscious. In other plants, I have seen reactions that were worse than the Direct Action Everywhere video footage. The differences in the pig’s reaction were probably due to genetics. One factor could be that the Danish pigs were completely free of the PSS Porcine Stress Gene. It is likely that there are other genetic factors, in addition to the PSS gene.

Pig genomics and CO₂ stunning

Just before COVID shut everything down, I had a project all set-up to have one of my graduate students do genomic testing on the pigs that reacted calmly to CO₂ compared to the pigs that had a bad reaction.  My hypothesis was that bad reactions to CO₂ could almost be eliminated by selective breeding. My student worked very closely with a large plant. The management team was very interested in looking at pig genetics. She had Go Pro cameras and lights installed in their CO2 machine and a reasonably priced genomics test had been located. Several days before the project was going to start, the managers of the pig farm who owned the plant cancelled the project. They did not want to look inside the box. After this happened, no other plant was willing to participate in this project. I want to compliment the forward- thinking plant management who were totally behind doing this research. One of the top managers who we worked with, now has a new job in the beef industry. The pig farm managers who cancelled my project were extremely short sighted. Now the Direct Action Everywhere video may force the industry to look inside the box.      

When the CO₂ system is being evaluated, both the stress of handling and the stress of stunning must be considered. Group CO₂ systems have really good low-stress pig handling and electric prods can be totally eliminated. To stun pigs with electricity in a large plant requires lining pigs up in a single file alley. Total elimination of electric prods in this system is not possible. Electrical stunning produces instantaneous insensibility. In large plants, an electric prod will have to be used on about 15% of pigs. Where I draw the line on an acceptable tradeoff between improved handling versus the stress of anesthesia induction is when pigs actually attempt to escape form the gondola where the CO₂  is administered. The industry needs to address this issue.