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HSVMA Fact Sheet:

Ventilation Shutdown (VSD) as a Means of Depopulation of Animals

The Humane Society Veterinary Medical Association opposes the use of heatstroke as a method of mass killing pigs, chicken, turkeys, and other poultry. Heatstroke-based animal depopulation methods include:

  • Ventilation Shutdown (VSD), in which ventilation systems are sealed and animals’ body heat raises the barn or shed temperature until animals die of heatstroke
  • Ventilation Shutdown Plus Heat (VSD+Heat), in which heaters are used to raise the temperature
  • Ventilation Shutdown Plus High Temperature and Humidity (VSD+TH), in which heat and steam are added to the barn
  • Ventilation Shutdown Plus Steam (VSD+Steam), in which steam is used to raise the barn temperature

In 2020, VSD+TH was used to kill approximately 250,000 pigs who could not be slaughtered due to COVID-19-related supply chain disruptions. In 2022, 1 in 9 laying hens in the U.S. were depopulated due to highly pathogenic avian influenza (HPAI, or bird flu). Most were killed in depopulations in which VSD+Heat was used as the sole depopulation method or one of multiple methods used. VSD+Heat continues to be used frequently in HPAI depopulations.

Widespread use of heatstroke-based depopulation methods began soon after the American Veterinary Medical Association released its 2019 Guidelines for the Depopulation of Animals, which classify VSD+Heat as “permitted in constrained circumstances.” The HSVMA encourages reclassification of this method as “not recommended.”

While we recognize that veterinarians sometimes have a duty to end the lives of animals and that ending the lives of large numbers of animals in an emergency can be challenging, we maintain that the veterinary profession’s responsibility to protect and advance animal welfare requires eschewing killing methods that cause prolonged and/or severe suffering. The European Union and the United Kingdom have banned many of the methods of depopulation used in the United States and have used more humane methods to end the lives of birds affected by HPAI.

The HSVMA encourages the development and use of more humane methods of depopulation and mass euthanasia. We encourage incorporation of animal welfare considerations into all aspects of animal disaster management, including taking steps to decrease the risk that veterinary patients will have their lives ended through depopulation.

For more information on this topic, please see this Animals journal article, co-authored by veterinary leaders of HSVMA: The Rise of Heatstroke as a Method of Depopulating Pigs and Poultry: Implications for the US Veterinary Profession.

If you are an AVMA member and would like to reach out to your AVMA delegate to engage them in discussion of this important issue, please see our Talking Points. To become involved in advocating for the elimination of heatstroke-based depopulation methods, please contact [email protected].