Perceptions of swine industry stakeholders on the use of water-based foam, high-expansion nitrogen foam, and carbon dioxide gas as methods of swine depopulation

Abstract

Emergency contingency plans for the U.S. swine industry, including depopulation protocols, that are essential to limit the spread of sudden outbreaks of infectious diseases is currently lacking. Although novel depopulation methods such as water-based foam (WBF) and high-expansion nitrogen foam (N₂F) are being investigated, carbon dioxide gas (CO₂) is currently the only American Veterinary Medical Association (AVMA)-preferred method capable of depopulation of groups of swine. The AVMA’s assessment of depopulation methods evaluates efficacy, animal welfare implications, and caretaker physical and mental health, in addition to logistical aspects of equipment acquisition and use. These criteria are best gauged using input from individuals familiar with the operations within the swine industry. Therefore, the aim of this study was to describe swine industry stakeholders’ perceptions of WBF, N₂F and CO₂ depopulation after a large-scale field demonstration. A survey was created based on the criteria outlined in the AVMA Depopulation Guidelines to determine respondent perceptions of each method. Swine industry stakeholders of various backgrounds (N=32) were recruited and invited to observe demonstrations of each method. Mixed linear regression models were built to investigate the association between survey question scores and depopulation method. Respondents varied in occupation, with 37.5 % (12/32) belonging to an academic institution or veterinary medical association, 21.9 % (7/32) to a pork organization, and 18.8 % (6/32) to state or federal regulatory agencies. The remaining 21.8 % (7/32) was a group consisting of one producer (3.1 %), one individual in swine industry retail (3.1 %), one veterinarian in a private practice setting (3.1 %) and four (12.5 %) who did not disclose their affiliation. Average experience (±SD) in the swine industry was 14.4 (±12.4) years, and 40.6 % (13/32) had previous experience of any type in swine depopulation. The overall method impression scores revealed that WBF and N₂F were perceived as better options compared to CO₂ (P < 0.001). WBF and N₂F scored higher on pig distress mitigation, protecting emotional and psychological health of personnel, and equipment accessibility compared to CO₂ (P < 0.001). Stakeholders without a clear affiliation provided higher scores compared those affiliated with regulatory agencies, pork associations or academic or veterinary institutions, regarding minimizing pig distress, method safety/accessibility, and overall method impression. Few demographic differences were observed, suggesting similar perceptions of the three depopulation methods during the demonstrations. This industry feedback is valuable for future considerations, method improvements and facilitation for possible implementations into future response plans.