The US poultry industry has increasingly switched to “the most inhumane method available” to cull tens of millions of birds during the latest outbreak of avian influenza, according to government data.
Outbreaks of the disease, also known as bird flu, have wreaked havoc across Europe and the US this year, with 38 million birds killed in the US so far.
But how these birds are killed has generated controversy, with veterinarians and animal welfare campaigners urging an end to the use of the ventilation shutdown method, which kills animals by sealing off the airflow to the poultry sheds and increasing temperatures to lethal levels.
Workers have described the method as like “roasting animals alive”. European officials have said it should not be used in the European Union.
In the US, however, the American Veterinary Medical Association (AVMA) lists ventilation shutdown with supplemental heat as “permitted in constrained circumstances” for “depopulation”.
A new analysis has found that it has now become the main method for killing birds, used in nearly three-quarters of culls.
The analysis of US Department of Agriculture (USDA) data by the Animal Welfare Institute found 73% of culls in the US in February and March (the most recent period for which data is available) involved the use of ventilation shutdown.
This represents a dramatic shift from the last bird flu epidemic, in 2015, which resulted in the killing of 50 million farmed birds in the US. During that outbreak, the animals were predominantly killed by carbon dioxide poisoning or smothered in a blanket of firefighting foam.
“The default method of killing seems to have changed from foam to ventilation shutdown,” said Dena Jones, director of the AWI farm animal programme, who said the design of poultry housing “ensures they won’t be able to humanely kill them”.
A USDA spokesperson said “some housing designs do not allow for effective depopulation using foam” and that the carbon dioxide method was “hindered by supply shortages”. The department financially compensates farmers for culling animals.
Activists have protested against the widespread use of ventilation shutdown, most notably by disrupting basketball games to draw attention to Glen Taylor, the billionaire owner of the Minnesota Timberwolves team who also owns an Iowa egg farm where 5.3 million hens were killed using ventilation shutdown.
A coalition of vets and animal rights advocates urged the AVMA to reclassify the method as “not recommended”. The lack of response so far from the AVMA “harms animals and the veterinary profession’s reputation as caring advocates for animals”, according to Crystal Heath, a vet and co-founder of the ethical veterinary group Our Honor.
In the EU and the UK, birds are culled with carbon dioxide gas or nitrogen-infused foam, which are considered to be more humane methods than using firefighting foam when carried out correctly because they render the animals unconscious before killing them, Jones said.
The European Food Safety Authority says ventilation shutdown should not be used, but there have been reports of producers in France being given emergency permission to use it.
The EU also considers the use of firefighting foam to kill birds as inhumane because it entails “drowning in fluids or suffocation by occlusion of the airways”.
The USDA did not respond to a question about whether any steps were being taken to require less painful cull methods or prevent ventilation shutdown from becoming the default in future outbreaks.
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