In the summer of 2018, African swine fever virus was detected in China, highlighting the need renewed preparation efforts in the United States against foreign animal diseases. Since 2018, many efforts have focuses on improved surveillance, response by federal and state animal health officials as well as identification of gaps in the swine industry in the event of a FAD incursion on US soil. One of these gaps was methods to successfully perform mass depopulation of swine herds in such a way that is efficient, safe, welfare-friendly and does not cause undue emotional strain on farm staff. One method of mass depopulation that took center stage during the COVID 19 pandemic was the use of carbon dioxide gas as a means of mass depopulation. Due to staff shortages at processing plants, populations of pigs were euthanized. In most cases the method of euthanasia was carbon dioxide. Despite the documented efficacy of this method, pig level variables such as movement, vital signs, and temperature had not been explored. These variables are quintessential to understanding and ensuring that the animal welfare aspects of a mass depopulation method fall within the AVMA Guidelines for Depopulation of Animals. Therefore, the objective of this work was to evaluate the effectiveness and animal welfare implications of administering the inhalant anesthetic, carbon dioxide (CO2) in a 12-foot dump trailer as a method of humane euthanasia for sows, grower and market weight pigs. In brief, a 12-foot dump trailer was modified into a CO2 chamber for this study. CO2 was delivered into the trailer through a 100-foot tube attached to a vaporizer, receiving CO2 from a CO2 tank. Groups of pigs were moved into the trailer and administered CO2 at a rate of 20-30% of chamber volume per minute over a 5-minute wash in period. After 15 minutes, pigs were assessed for confirmation of death. Oxygen and CO2 levels were monitored throughout the entire trial period. No secondary means of euthanasia was necessary. The first two groups consisted of 3 sows each which received sedatives to ensure that the process worked without causing undo stress on the animals. Two groups of grower pigs, two groups of sows and one group of market weight animals were successfully euthanized using the CO2 trailer. In each group, three animals were monitored for movement using a HOBO-Pendant G accelerometer and heart rate using Cardiac Insight ECG. Results from these tools indicate that cessation of movement occurred within 282 seconds as an average across all groups and cessation of heartbeat was confirmed in all groups. The observations from this study support the use of CO2 as a method of mass depopulation due to the ease of use, animal welfare implications, ability to perform with large groups of animals, human safety and efficiency.

Key Findings:
• Dump trailer can be successfully modified for use as a CO2 chamber
• CO2 inhalant anesthetic can be used to successfully euthanize large groups of pigs of multiple sizes
• Cessation of movement occurred on average across multiple age groups within 282 seconds after exposure to CO2.