The US swine herds are susceptible to the introduction of catastrophic diseases that may require mass depopulation to contain. While the industry is well versed on individual animal euthanasia, mass depopulation of mature swine present unique challenges due to their size and densities in which these animals are raised. No single method of depopulation fits all scenarios or species, and multiple methods likely will be required to complete tasks in a timely, biosecure manner. Most current methods for swine depopulation and disposal are not good candidates for mass depopulation in sow units because they are either time consuming (delivered at the individual level), create an unacceptable risk of disease dissemination for other swine populations (e.g. pathogen dissemination during movement of carcass material to disposal sites), or are practically infeasible to facility designs. In this project, we combined the depopulation and disposal steps by using rendering trailers as depopulation chambers.

We evaluated the following depopulation agents: carbon dioxide gas (CO2), nitrogen gas (N2), compressed air foam (CAF), CAF made with nitrogen gas (CAF-N2), and aspirated foam (AF). We used a gated approach where we assessed our ability achieve success at each step before moving to the next step. First was the ability fill the container in a rapid manner. Second, each treatment was used in a small scale trial on anesthetized sows. Third, each treatment was used in a small scale trial on conscious sows. Fourth, one agent (aspirated foam) was used for a large-scale field trial.

While all methods were successful, aspirated foam had the shortest mean time to the cessation of movement, which was why it was selected for the large-scale field trial. Our results show that aspirated foam was comparable to the leading method of CO2, but had fewer potential pitfalls than CO2 (availability and sourcing CO2, vaporizing, delivery time, etc.). In our large-scale trial using aspirated foam, the average time to cessation of movement was 128 seconds for groups of 45 sows, which means that large sow farms could be depopulated rapidly with this method.

Water-based foam (WBF) depopulation is a preferred method in poultry, leading to rapid death and relatively ease of application and USDA has WBF generating units in the National Veterinary Stockpile, which makes it an attractive agent. Historically, foam has not been feasible in swine due to their housing; however, use of a trailer provides new opportunities. Our study shows that WBF for depopulation of sows in modified rendering trailers is a viable option for mature swine (and likely younger pigs too).

When a FAD is introduced to the US swine herd, the way to lessen the economic impact to producers is by preventing further spread in the national swine herd. The ultimate objective of project was to establish an effective method to facilitate both the depopulation of sow units and the disposal of carcasses in the face of an FAD outbreak. We demonstrated that use of inhalant-based depopulation methods on sows in modified rendering trailers can be a cost-effective and efficient method for stamping-out FAD-affected sow farms. Using an inhalant-based depopulation method in rendering trailers will allow for containment of a FAD as quickly as possible to help maintain continuity of business for non-infected animals and non-contaminated animal products.

Contact Information: Andrew Bowman,