Controlled-atmosphere stunning (CAS) offers no significant welfare advantage over conventional low-voltage electrical stunning in the commercial processing of chickens, reports a study.
Animal welfare experts have long had mixed views on which stunning practice is more humane. “The research around CAS was incomplete, so we were interested in participating in this study to test this technology and better understand its potential to improve animal welfare,” said Dr. Ken Opengart, who oversees Keystone’s animal welfare practices.
“Testing these practices in a commercial environment was critical to understanding the issues,” said Dr. Kellye Pfalzgraf of Tyson.
The study looked specifically at the pros and cons of each stunning method at the commercial level, said Todd Bacon, US quality systems for McDonald’s US supply chain. He noted that the alpha phase focused on the methodology and equipment itself — understanding the right mixture and administration of gases to stun effectively while monitoring the bird reactions during the process.
The beta test, he said, incorporated what was learned from the alpha phase to further test the best CAS process at the commercial scale in production.
The study involved installing CAS equipment in a commercial setting and monitoring for a period of 16 production days. During the process, Bacon said a number of different factors were measured, including animal welfare and handling, carcass yield and product quality.
The recent work by McDonald’s follows a white paper the company prepared on CAS in mid-2005 that also concluded that substantial evidence did not exist at the time to warrant a switch to CAS (Feedstuffs, July 11, 2005).
“This work was to review what we’re doing today and what we should be doing tomorrow, and it’s part of our continuous improvement process that will continue on,” said Bacon.
While the Humane Society of the United States (HSUS) and People for the Ethical Treatment of Animals (PETA) are opposed the conventional electrical stunning practice, the American Humane Association (AHA) does not endorse one method over another.
“We are not aware of any science-based, conclusive evidence that the distress chickens experience in existing electric stunning methods is either greater or less than that with gas anesthesia induction. Any claim that CAS is more humane is simply not founded on current science and should not be forced on the industry,” said AHA president Marie Wheatley.