“Depopulation” By Heatstroke: An Ethical Crisis
The “depopulation” of farmed animals involves the mass killing of a large number of individuals at a single location, usually because of disease outbreaks or supply chain disruptions. Since 2019, there has been a rise in the usage of heatstroke as a method of depopulation in the U.S., although evidence suggests it causes extreme animal suffering.
Due to the severity of the suffering and a rise in the number of animals killed via heatstroke, the authors of this paper urge the veterinary profession to acknowledge its responsibility to protect animal welfare and push for changes to what depopulation methods are deemed acceptable.
According to American Veterinary Medical Association (AVMA) guidelines, the preferred methods of depopulation include death by gunshot, electrocution, and inhaled agents (i.e., lethal gas). Facility owners may face constraints in using these methods due to rapid disease spread, a lack of specific depopulation equipment, or the need to maintain distance between workers and animals. However, they will not receive compensation if they use any method that is categorized as “not recommended” or not mentioned in the guidelines.
According to the AVMA guidelines, heatstroke-based depopulation methods or ventilation shutdown (VSD) are classified as “permitted in constrained circumstances.” This method involves blocking ventilation routes in farmed animal housing and using the animals’ body heat to increase the temperature until all of the animals die. There are variations of VSD, such as adding heat (VSD + H), humidity (VSD + TH) or gas (VSD + CO2). In commercial settings, it may take anywhere from four hours to over eight hours for farmed birds to die through VSD, while nursery pigs were recorded dying in 90 minutes and adult pigs within 110 minutes during an incident where VSD + H was used.
Heatstroke can cause distributive shock, gastrointestinal bleeding, vomiting, abdominal inflammation, and organ failure, among other problems. Alongside the physical pain, pigs and farmed birds may experience anxiety, helplessness, disorientation, and aggression. Burns can occur in VSD + TH, including deeper-layer burns that occur before superficial damage is noticeable when temperatures reach 158°F with humidity at 75%.
In response to the Highly Pathogenic Avian Influenza outbreak from 2014-2016, the Animal and Plant Health Inspection Service (APHIS) endorsed the use of heatstroke-based methods as they were deemed quicker than waiting for depopulation equipment. Since then, VSD has also been increasingly used in response to supply chain disruptions on U.S. farms. For example, in 2021, VSD + TH was chosen over AVMA’s preferred methods to euthanize 243,016 pigs due to COVID-19-induced supply chain disruptions. Additionally, from January to August 2022, between 9.1 and 36.6 million chickens, turkeys, and ducks were killed by VSD + H.
The authors mention AVMA’s Principles of Veterinary Medical Ethics, noting that veterinarians should prioritize patient needs to prevent and alleviate suffering. The authors therefore argue that the U.S. veterinary profession has two obligations: to promote the use of humane depopulation methods and to explore ways of preventing depopulation.
Revising the AVMA guidelines offers a chance to assess the effectiveness and ethics of current methods. According to the authors, there is concerning evidence that heatstroke methods exceed recommended durations and cause pain. They recommend reclassifying VSD-based methods as “not recommended” or exclude them entirely from the guidelines.
The authors also recommend that the AVMA use the results of other countries’ animal welfare assessments to guide depopulation recommendations. An assessment performed in the U.K. led to the promotion of a new depopulation method of high-expansion nitrogen-filled foam and a plan to ensure that facilities have the required equipment to handle disease cases within 48 hours.
The authors argue that efforts should also be made to reduce the need for depopulations by identifying the causes of supply chain bottlenecks. Intensive pig farming is very vulnerable to disruptions because housing is already at near-full capacity, reducing available space to take incoming animals and leading to aggression when animals are packed together. Instead, housing fewer pigs in each facility may ensure animals have access to food and water and won’t become aggressive toward each other when bottlenecks happen. With 0.5-7 million birds often housed on one site, intensive bird farms are also vulnerable to depopulation as they lead to rapid disease spread. Such stocking densities can also make it harder to achieve 48-hour depopulations.
Veterinary professionals can help by collaborating with the AVMA to reduce the maximum number of animals allowed per facility and offering facility owners guidance in addressing supply chain disruptions. Requiring facilities to demonstrate that they can meet the 48-hour depopulation requirements without using VSD may also be beneficial. More generally, veterinary professionals can promote the importance of being a responsible producer who strives to give a humane death to animals during depopulation.
Depopulation of food-producing animals is harrowing for both the affected animals and the workers who witness it. Millions of animals suffer as a result of heatstroke-based killing, and the authors note that more individuals will likely experience this painful fate moving forward. While advocates can raise awareness of this issue and lobby for change within the government, the onus is also on veterinarians to work alongside them to end this cruel practice.
https://www.mdpi.com/2076-2615/13/1/140