WASHINGTON, D.C. — The Humane Society of the United States (HSUS) criticized USDA approval of the ventilation shutdown (VSD) method to depopulate some poultry during the recent H7N8 avian influenza outbreak in Dubois County, Ind.

VSD disables poultry house ventilation systems, raising building temperatures to the point of bird mortality. It was formally used in three Dubois County poultry barns, according to Denise Derrer, public information director for the Indiana State Board of Animal Health (BOAH).

Criticism of the method came in a Jan. 22 press release from HSUS, which also highlighted opposition to VSD in a “Humane Alert” email sent Jan. 26. HSUS opposes VSD in any situation, said Paul Shapiro, its vice president of Farm Animal Protection. “The problem with VSD, which is just a euphemism for live baking, is it can take a long time,” he said.

Time is at the center of the debate over the method. USDA policy is to depopulate a farm flock within 24 hours after testing positive for highly pathogenic avian influenza, or HPAI. Foaming, the mass application of water-based foam to birds, is the main depopulation method during HPAI outbreaks. Foaming results in bird mortality within 15 minutes, according to University of Delaware poultry scientists who developed the method.

Foaming equipment can be finicky in cold temperatures. It took six days to depopulate nearly 260,000 commercial turkeys and 150,000 laying hens on 10 farms, near Jasper. Dubois County turkey owners also immediately shut down fans in turkey barns where H7N8 was confirmed, to prevent aerosol spread of the virus to neighboring farms. That did result in some poultry mortality before foaming, according to BOAH.

Shapiro said there are more painless ways to accomplish depopulation. “The more humane method is using inert gases,” like argon or nitrogen, he said.

Gassing poultry with inert gasses, which displace oxygen, is thought to be more humane. According to the UD poultry scientists, large-scale applications of inert gas for poultry depopulation are difficult. Very high gas concentrations are required, and human health hazards are greater than in foaming.

Carbon dioxide can be used, but that also presents human health hazards in larger-scale applications. Use of carbon dioxide instead of inert gasses may be less preferable from some animal welfare standpoints, according to Bernard Rollin, Colorado State University bioethicist.

That’s because the animal may be more likely to be cognizant of an experience of pain with carbon dioxide, as opposed to inert gasses.

Rollin said large-scale poultry depopu-lation during disease outbreaks presents challenges for how the animal agriculture industry relates to its customers. “We’re dealing with a time in history when the public is extremely concerned with the treatment of animals,” he noted.

The USDA guidelines for responding to HPAI define VSD as “an adjunct method” for poultry depopulation. “This method is considered by some to be less humane than other methods, but it can spare the lives of potentially thousands of other birds by halting the infection as soon as it is detected,” state USDA guidelines.