Use of water-based foam to achieve rapid depopulation of swine: Assess physiological and behavioral effects in swine exposed to 5 different water-based foam products

Scientific Abstract

Prevention of outbreaks and transmission of foreign animal diseases (FAD) is a high priority for the U.S. swine industry. Using existing depopulation guidelines for future contingency plans may be challenging due to limited scaling opportunities as most methodologies are deployed on an individual level. Water-based foam (WBF) has previously been approved for herd-level depopulation of floor-raised poultry. Previous studies by this research group have determined WBF using Phos-Chek WD881 Class A foam to be a promising candidate for rapid depopulation of large populations of swine. However, there are currently more than two dozen Class-A foams on the U.S. market that remain untested. In addition, novel nitrogen-gas foam- (N₂F) and CO₂ depopulation methodsare undergoing evaluation and may be suitable alternatives to WBF. Thus, the objectives of this study were to 1) evaluate currently available Class A foam concentrates for swine depopulation suitability, 2) assess short-listed Class A foam concentrates from Objective 1 for depopulation efficacy and potential negative impacts on swine welfare, 3) describe and calculate the operational parameters of Class A foam depopulation by animal throughput and cost estimates for swine depopulation of different herd sizes and production types, 4) describe and compare method efficacy and behavioral outcomes between WBF, N₂F, and CO₂-gas depopulation methods (will be presented elsewhere in report by Dr. Williams), and 5) describe attitudes and perspectives of swine industry stakeholders on WBF and CO₂-gas depopulation methods.

Sixteen Class A foams were sourced and tested for suitability using previously established foam generating systems with gas-driven water pumps and dual expansion foam nozzles in 15-cubic yard containers. Fill time and decay rates were measured for 0.5, 1, and 3% foam-water concentrations. Out of 16 obtained Class A foams for assessment, four foams (BioEX BioFor N Class A Foam, FireIce Polar Class A EcoFoam, Buckeye Platinum Class A Foam, and National Foams Knockdown Class A Foam) beside Phos-Chek WD881, showed promising properties for additional field testing using live pigs in a modified 84.4 cubic-yard hydraulic rendering trailer. The average price for these foams was $26.4 USD/gallon with an average fill time of 54.9, 55.4 and 51.5 seconds and a decay rate of 0.26, 0.22 and 0.12 inches/minute, for 0.5%, 1.0% and 3.0% foam-water concentrations, respectively.

To assess any short-term physiological reactions to the shortlisted foams, 75 nursery pigs were divided into five replicates of three, with each triplet of pigs lowered into a polyethylene bulk container. Foam was filled up to the shoulder height (approximate 12-18 inches). Pigs were allowed to move around in the foam for 15 minutes while being observed for any visible reactions to the foam. After 15 minutes, additional foam was applied, covering the animals, and filling the container with a dwell-time of 7.5 minutes. After a 7.5-minute dwell-time pigs were removed from the container. Overall, the degree of pulmonary hemorrhages was significantly different between foam groups (P=0.04), with Phos-Chek WD811 inducing a higher number of pulmonary hemorrhages scores of three and four compared to Biofor N (P=0.043). No other physiological differences were observed.

For the field trial, 16-17 pigs across three replicates per short-listed foam, were loaded into the trailer, which was filled up until overflowing and left for a 7.5-minute dwell time. The average fill time (±SD) and time to last recorded movement or sound coming from the trailer post-foaming was 81.2 (21.5) seconds and 123.1 (50.7) seconds, respectively. All foams performed well during the depopulation process. No pigs showed any signs of regaining consciousness after the 7-5-minute dwell time and all pigs were declared deceased upon inspection.

Using the data generated from the foam generating setup, foam specifications and associated costs, a self-populating excel spreadsheet for calculating depopulation costs and timelines were constructed for swine producers wanting to estimate preparedness costs for different foam options.

To determine the attitudes on the use of WBF, N₂F, and CO₂-gas depopulation methods, swine industry stakeholders of different backgrounds were invited for a live demonstration of these methods. They were also recruited to participate in a survey covering 11 key assessments and a final overall impression per demonstrated method. In total, 32 participants reviewed the three depopulation methods, and the overall highest scored and ranked method was WBF followed by N₂F and CO_2.

The findings from this study revealed four new possible Class A foam products suitable for swine depopulation that could be added to a future stockpile to avoid bottlenecks in times of FAD emergencies, if WBF depopulation is approved. This study also revealed important attitudes and perspectives from swine industry stakeholders on WBF, N₂F and CO₂-depopulation. These results will help with future considerations and refinements of method protocols to ensure stakeholders the best possible outcome for both staff and animals during emergency scenarios.