Reliability of water‐based medium‐expansion foam as a depopulation method for nursery pigs and cull sows

Abstract

Animal disease preparedness plans including depopulation guidelines are paramount to prevent the spread of emerging infectious diseases but difficult to implement for swine under field conditions. However, water‐based foam (WBF) is currently an approved and successfully deployed depopulation methodology in poultry. Therefore, the reliability of WBF as a depopulation method and the effectiveness and irreversibility of consciousness and consequential mortality in pigs of different ages was assessed across two trials. Trial 1 investigated the time to loss of consciousness and cessation of cardiac activity in nursery pigs (n = 72) at six different foam immersion time points (2.5, 5, 7.5, 10, 12.5 and 15 min) when placed in a 1.47 m3 (1.2 × 1.2 × 1.02 m, length × width × height) plastic bulk container. One pig per replicate was implanted with an ECG bio‐logger. Irreversible loss of consciousness was observed after a 5‐min immersion. The average (SD) time to development of a fatal arrhythmia from the initiation of the foam application was 7.3 min (1.82 s). Trial 2 aimed to validate the findings from Trial 1 in 75 larger cull sows across three replicates (n = 25). Sows were loaded into a 41‐m3 sealed trailer (12.2 × 1.5 × 2.24 m), immersed in WBF and left undisturbed for 5 min post foam‐filling completion. Six pigs in each replicate were implanted with an ECG bio‐logger. A 5‐min dwell time resulted in irreversible loss of consciousness and subsequent mortality in all cull sows. The average time (SD) to cessation of movement and fatal arrhythmia post foam‐filling completion was 2.2 min (34.8 s) and 8.7 min (138.0 s), respectively. While a 5‐min immersion in WBF induced irreversible loss of consciousness and death in both trials, a 7.5‐min dwell time followed by observation for confirmation of death post WBF removal would be advisable for pigs of all sizes.

Water-based medium-expansion foam depopulation of adult cattle

“…In studies of WBF application in Pekin ducks, average time to COM ranged from 3.3 to 5.9 min and average terminal cardiac activity ranged from 4.3 to 5.0 min ( Benson, et al, 2009 ; Caputo et al, 2012 ). In swine, WBF has been reported to cause COM on average in 2.1 to 2.2 min in cull sows, 1.4 to 1.8 min in finisher pigs, and 0.8 to 2.8 min in suckling piglets ( Lorbach et al, 2021 ; Arruda et al, 2022 ; Kieffer et al, 2022 ). Average terminal cardiac activity after WBF has been reported as 8.7 min in cull sows and 7.3 min in nursery pigs ( Arruda et al, 2022 ).…”

“…In swine, WBF has been reported to cause COM on average in 2.1 to 2.2 min in cull sows, 1.4 to 1.8 min in finisher pigs, and 0.8 to 2.8 min in suckling piglets ( Lorbach et al, 2021 ; Arruda et al, 2022 ; Kieffer et al, 2022 ). Average terminal cardiac activity after WBF has been reported as 8.7 min in cull sows and 7.3 min in nursery pigs ( Arruda et al, 2022 ). Given that WBF is effective in multiple species, its versatility could be a suitable and universal option for farms housing a variety of species.…”

“…Cattle were loaded onto a 64.5 m 3 (dimensions 12.2 m × 2.36 m × 2.24 m; length, width, height) custom-modified rendering trailer through the rear sliding door of the trailer using a single file ramp as described by Arruda et al (2022) . Once cattle were loaded, three individual foaming systems were used in parallel and consistently in all trials.…”

“…A 1% foam-water solution was created by mixing PHOS-CHEK WD881 Class A foam concentrate (Perimeter Solutions, Rancho Cucamonga, CA, USA) in a 1,892-L water tank. The foam–water solution was pumped from the tank and delivered to the trailer as described by Arruda et al (2022) . With a foam expansion rate of approximately 40 to 50:1 foam to water, this was considered a medium-expansion foam.…”

“…In commercial poultry settings, WBF is considered a faster, more biosecure method of depopulation than carbon dioxide and does not negatively impact carcass composting ( Benson, et al, 2009 ). Recent studies have also shown success in depopulating suckling, nursery, finisher, and cull swine using WBF in a bulk container or modified rendering trailer ( Lorbach et al, 2021 ; Arruda et al, 2022 ; Kieffer et al, 2022 ). Some mentioned advantages of WBF over current depopulation methods include ease of use, minimal personnel risk, and availability of equipment as supplies needed for WBF depopulation already exist within the USDA National Veterinary Stockpile ( USDA-APHIS ).…”