US agriculture officials are being lobbied to make it easier for chicken farmers to use the “cruellest option” for killing birds affected by the continuing bird flu epidemic. More than 49 million poultry birds in the US have either died as a result of bird flu or have been culled due to exposure to infected birds, echoing the havoc the disease has caused the European poultry and wild bird populations. Once an outbreak of bird flu is confirmed in a commercial flock, any remaining healthy birds must be culled under current US disease control rules. Producers are compensated by the government. In the US, “ventilation shutdown plus” (VSD+) – which brings on heatstroke by exposing large numbers of birds to high heat for a minimum of three hours – is now considered a last resort. Poultry producers have to get permission to use it after a case of avian flu is detected. Animal advocates have described the method as “basically cooking animals alive”. European officials list it among methods that “are likely to be highly painful” and “must never be used”. While killing animals by suffocation or heat stress would be illegal, industry experts have said that it would be possible to obtain a derogation in an emergency when no suitable alternatives are available. However, the National Association of State Departments of Agriculture (Nasda), a group representing state-level agriculture agencies across the US, has approved a measure asking the US Department of Agriculture (USDA) to consider making it a “preferred” method. This would mean that producers no longer have to seek approval to use it or show that they can’t implement one of the two currently preferred methods: carbon dioxide poisoning or firefighting foam, which suffocates poultry birds. So far this year, VSD+ has quickly become the poultry industry’s predominant cull method and has been used to kill tens of millions of chickens and turkeys. Animal welfare campaigners say the industry prefers ventilation shutdown because it is the “easiest and cheapest”. “Although the avian flu outbreak is global, only the US has put ethics completely aside and intentionally induced heatstroke to kill millions of animals,” said Dena Jones, director of the Animal Welfare Institute’s farm animal programme. Nasda said in a statement: “Nasda does not endorse single methods of depopulation, rather Nasda supports considering the uniqueness of each region, state and farm when making decisions regarding depopulation and recommends using methods that minimise the loss of life to animals.” The USDA’s rules for culling birds rely on American Veterinary Medical Association (Avma) guidelines, which state VSD+ is “permitted in constrained circumstances” – meaning it should be used only if preferred methods aren’t available. A group of 276 veterinarians have submitted a resolution to Avma to reclassify the method as “not recommended”, so that it isn’t used at all. However, the head of Avma’s animal welfare division, Cia Johnson, told an audience at a conference this summer: “We need data from you … some of these methods are at risk of leaving the guidelines, I think you probably have an idea of what those methods might be. We need data to support them staying in the document.” James Reynolds, a livestock veterinarian and professor at Western University of Health Sciences, said that Avma selectively seeking data to support VSD+ is “completely unreasonable. Not founded on reason, not founded on science.” Poultry producers have said that carbon dioxide shortages and logistical challenges with deploying firefighting foam have made ventilation shutdown a more attractive option. “Sometimes, in an emergency, foaming units and others cannot be secured quickly enough and the birds suffer longer if not euthanised immediately,” said Bill Mattos, the president of the California Poultry Federation, in an email. This year’s bird flu was expected to die down over the summer, but that hasn’t happened, either in North America or Europe. “Our summer heat has always killed much of the bird flu strains,” Mattos said. “But this year that totally changed throughout the US.”