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Is Ventilation Shutdown a cruel way for farm animals to die?

You might not have heard of “Ventilation Shutdown” as a method of euthanasing large numbers of farm animals simultaneously. But in some parts of the world it is legal and accepted. In this article, our farm vet Cassandra explores the controversial topic of “VSD”.

What is Ventilation Shutdown (VSD)? 

In livestock systems such as poultry and pig farms where animals are housed 24/7 in environmental conditions that are highly controlled (paradoxically for their welfare), ventilation shutdown means sealing sheds and buildings, stopping the fans used to circulate fresh air/remove harmful gases, and allowing the body heat and gases naturally produced by the animals and manure to slowly kill them. VSD+ is a slight modification of the above, in which not only ventilation is shut down but also ambient temperature is artificially raised, or where additional CO2 is pumped in the buildings. Both are aimed at speeding up the deaths of the animals. Death occurs by overheating and/or oxygen starvation, usually over a period of time that is near or over one hour; but in some cases animals may survive for up to 16 hours. 

What the research says

For example, a study investigating the suitability of VSD+ showed that the time required for pigs to become silent (i.e. to the point when no sounds are heard and no moving animals are seen) could range from 41-70 minutes in nursery piglets and between 47-83 minutes in finishing (nearing slaughter age) pigs. 

The maximum temperatures reached in the barns ranged between 64-73C. The AVMA (American Veterinary Medical Association) depopulation guidelines recommend that VSD+ be used only if it resulted in a > 95% death rate in less than 1 hour. Although far less than 1% of animals required manual euthanasia at the end of the study in question, it was slow.

The time needed for these animals to die seems unnecessarily long. 

Another study based in the UK showed that temperature alone is not adequate in measuring the ventilation capacity (or loss of) in a livestock building. In this study, two pig farms experienced loss of ventilation due to electrical issues and rising room temperatures occurred. Although in one farm pigs did not die as result of loss of ventilation/rise in temperature; it could be argued that the lack of incoming fresh air and the rising temperatures are likely to have been stressful for the pigs involved (mostly piglets and sows). In another farm of this study, the loss of ventilation/temperature rise in a dry sow building (where the sows stay in the later stages of pregnancy) caused animal losses, both directly (sow deaths) and indirectly (aborted litters).

In chickens, an experimental study that investigated VSD and VSD+ in caged egg-laying hens showed that the birds took between 1.5-3.75 hours to die. Although survivability using VSD in this experiment did not meet the flock depopulation standard of 100% lethality (as bird took the longest time to die with this method); the other two versions of VSD+ (increasing heat or pumping CO2) were deemed “equally effective” at reaching the 100% lethality. 

Where is VSD permitted?

In the USA, most importantly. The AVMA classes VSD as “not recommended” as a method of mass depopulation; however, VSD+ is currently still under review. AVMA guidelines intended that VSD+ should only be used in very extreme circumstances where animal health and welfare would otherwise be further compromised. For example; in cases of whole-barn major disease outbreaks of such severity that mass euthanasia is deemed in the best interest of the animals; or where there is a significant risk of a public health emergency (for example, highly pathogenic avian flu).

Unfortunately, the guidelines have been exploited during the COVID-19 pandemic to justify mass killing of otherwise healthy animals, purely on financial grounds. I.e. it was cheaper for some producers to destroy hundreds of thousands of animals this way; rather than using alternative, more welfare acceptable methods of culling animals that could not be sent to slaughter through the regular channels. 

Is this fair to the animals?

There is probably a reason why these methods are called methods of mass depopulation, rather than euthanasia. What is the meaning of euthanasia? This word comes from the Greek, meaning a “good death”. Although the definition of good death might differ slightly for different people and different countries; it is generally accepted that it should be painless, and provided to relieve from suffering. It could be argued that VSD/VSD+ methods do not provide “euthanasia”, as essentially the animals are subjected to increasingly high temperatures and lack of oxygen for the best part of an hour (far too prolonged a period of time). This is not a stress-free death. 

So here we are in the UK (and the rest of Europe), hotly debating which method of stunning at slaughter is best to achieve the quickest and least stressful death. And rightly being horrified at the thought of slaughter without prior stunning to achieve unconsciousness. And yet in other countries these unethical methods of mass depopulation seem to be getting more traction for all the wrong financial reasons. 

A group of American vets, Veterinarians Against Ventilation Shutdown, has been campaigning for the AVMA to reclassify VSD+ as ‘not recommended’. It is hoped that if AVMA listened to these major welfare concerns, the use of these unethical methods could be made more difficult and truly only limited to very extreme and unprecedented animal or public health-related circumstances.

Thankfully, these methods of mass depopulation are currently illegal in the UK – and we hope it stays that way.

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