As all of you know, coronavirus disease 2019 (COVID-19) has had a dramatic impact on the swine industry. Human exposure has resulted in significant decreases in processing plant capacity which led to an inevitable backlog of market swine. Processing capacity in the United States is approximately 510,000 head per day resulting in a weekly capacity of somewhere between 2.75 million and 3 million head per week. At its lowest, daily capacity dropped to approximately 42% during April 2020. That means approximately 215,000 hogs per day were not able to be harvested at that time.
Overall, it is estimated that, during the 2 months in which the industry suffered significant processing disruption, 2.5 to 3 million market-ready hogs were unable to go to market. Veterinarians and producers alike expressed concern that, unless something could be done, massive depopulations were likely going to be necessary. Having to depopulate large numbers of animals due to a non-disease related market disruption was a situation the industry had never considered.
Fortunately, farmers and veterinarians are very industrious. They have been able to find alternative outcomes for many of these animals. Utilizing efforts to hold animals in place, slow growth, repurpose vacant facilities, adopt non-traditional marketing strategies, altering breeding programs, etc have enabled producers to avoid or delay much of the anticipated depopulation.
Ultimately, however, depopulation has been unavoidable for thousands of animals. This is obviously something none of us involved in swine production wants to have to do. Having to depopulate healthy animals goes against every fiber of our being. The question then becomes how to best conduct the depopulation. The American Veterinary Medical Association’s (AVMA) Guidelines for the Depopulation of Animals serves as an important resource to help guide veterinarians’ efforts to work with their clients to find the most practical solutions.
The AVMA Guidelines importantly draw the distinction between euthanasia and depopulation defining depopulation as the rapid destruction of a population of animals in response to urgent circumstances with as much consideration given to the welfare of the animals as practicable. The document outlines the criteria necessary when considering methods of depopulation. In the swine section, the authors divide the acceptable methods into a preferred category and a category of methods designated as permitted under constrained circumstances.
The AASV Pig Welfare Committee developed a policy statement adopted by the AASV Board of Directors recommending that “priority should be given to those methods classified as ‘Preferred’” but went on to recognize that the “circumstances surrounding the COVID-19 processing disruption may require the use of methods classified as ‘Permitted in Constrained Circumstances’.” Producers and veterinarians have to evaluate a number of factors including animal welfare, human safety, human mental well-being, regulatory factors, availability of necessary resources, time constraints, number and size of the animals, social distancing considerations, etc before making the final decision regarding which method is most appropriate on an individual farm or system.
There is no one-size-fits-all method that works in every case. In the end, several preferred methods were used including gunshot, captive bolt, and carbon dioxide. In some cases, however, it was determined that a method not listed as preferred, such as ventilation shutdown plus (VSD+), would have to be used. No matter what method is chosen, it is important that the method is performed in a manner that achieves the criteria outlined in the AVMA’s guidelines for an acceptable outcome.
Of these methods, VSD+ is probably the most controversial. Unfortunately, there is not much scientific analysis of the physiological effects of hyperthermia in swine. The AVMA guidelines stipulate that use of this method should include the addition of heat or carbon dioxide to achieve at least 95% mortality within 1 hour. In practice, it was determined that the addition of humidity and heat facilitated the ability to achieve a successful outcome. These criteria are difficult to achieve on the average farm. If this method is to be used, it is imperative that a veterinarian supervise the process and that facilities be provided that ensure these minimal standards are met. This means that it is unacceptable to just roll up the curtains, shut off the ventilation, and walk away. As a method of last resort, VSD+ must be monitored, highly engineered, and process-controlled. Trained personnel must be present to humanely dispatch any survivors at the one-hour endpoint.
The veterinarians who have been involved in conducting VSD+ have established some baseline standards including increasing the temperature to 120°F within 30 minutes with the addition of steam to maintain at least 80% relative humidity. Facilities were modified at a significant cost to ensure the adequate application of heat and humidity and to facilitate the removal of the carcasses. Given these parameters, they reportedly were able to achieve at least 99% mortality within 60 minutes. Even under these conditions, VSD+ has significant drawbacks including a lack of information regarding the physiological impacts of hyperthermia, length of time to death (especially when compared with preferred methods resulting in comparatively rapid death), and public perception. Additional research is needed to determine whether or not VSD+ is an acceptable method of depopulation and, if so, under what specific criteria.
As you know, the activist groups have targeted VSD+ as cruel and inhumane. That is to be expected. They have their own agendas. The somewhat disappointing pushback has come from within our own profession. A small but vocal group of veterinarians have spoken out against depopulation for market disruption and especially against VSD+. While I support everyone having and expressing their opinion, it is disappointing that members of our own profession often do not bother to reach out and try to learn why things are being done the way they are before attacking their fellow colleagues.
Most of their attacks have targeted AVMA for producing the guidelines on depopulation and, most directly, for including VSD+ in those guidelines. To their credit, the AVMA has tried to explain the process they went through to develop those guidelines (it took a couple of years, over 60 volunteers, multiple reviews, and a public comment period) and has stood behind their document. I applaud their efforts to educate our colleagues and the public.
To that end, we must make sure that we do our part to ensure we follow the stipulations and criteria outlined in those guidelines. When faced with the need to depopulate a group of animals, veterinarians should work closely with their clients to prioritize those methods that are listed as preferred. Only after considering all those options, should we elect to resort to a method not listed as preferred. When choosing a method not categorized as preferred, extra steps should be taken to ensure compliance with the criteria that allow for the use of those methods. Remember, first and foremost, veterinarians speak for the pig.
Harry Snelson, DVM
Executive Director