Description of electroencephalographic data gathered using water-based medium-expansion foam as a depopulation method for nursery pigs

Abstract

The United States’ swine industry is under constant threat of foreign animal diseases, which may emerge without warning due to the globalized transportation networks moving people, animals, and products. Therefore, having disease control and elimination protocols in place prior to pathogen introduction is paramount for business continuity and economic recovery. During extraordinary circumstances, it may become necessary to depopulate large populations of animals, including swine, as a disease containment measure. Currently approved depopulation methods for swine present significant logistical challenges when scaled to large populations or performed in field conditions. In the United States, water-based foam is currently approved for poultry depopulation, and recent field studies demonstrate water-based foam is an effective depopulation alternative for swine. While effective, the speed at which water-based foam induces loss of consciousness prior to death, a major welfare consideration, has not been adequately investigated. In this study, 12 nursery pigs were terminated using water-based medium-expansion foam to quantify the time to induce loss of consciousness and ultimately brain death. Each pig was implanted with subdermal electrodes to capture electroencephalographic data, placed in a body sling, and suspended in a plastic bulk container that was subsequently filled with water-based foam. Electroencephalographic data was recorded for 15 min, during which the pigs remained immersed in the water-based foam. Conservatively, average (± SD) time to unconsciousness and brain death was 1 min, 53 s ± 36 s and 3 min, 3 s ± 56 s, respectively. The relatively rapid loss of consciousness compared to other methods limits the amount of distress and is overall a positive finding for the welfare of the pigs that might be depopulated with water-based foam. The findings of this study add additional evidence supporting the use of water-based medium-expansion foam for an emergency depopulation of swine.

Water-based medium-expansion foam depopulation of adult cattle

“…In a study that utilized EEG and external accelerometers in calves euthanized via captive bolt, unconsciousness occurred in 0 s, but convulsions lasted up to 13.8 min ( Collins et al, 2020 ). A study in WBF-depopulated nursery pigs demonstrated using EEG that unconsciousness occurred in 1.9 min and brain death in 3.1 min, supporting that time to COM is an overestimate of time to loss of consciousness ( Korenyi-Both et al, 2022 ). Therefore, it is likely that COM overestimates the time to unconsciousness in cattle and represents a conservative estimate of unconsciousness, which is the parameter most relevant to animal welfare during euthanasia or depopulation.…”

The use of high expansion foam for stunning and killing pigs and poultry

“…Publications describing the use of water‐based foam, low and medium‐expansion foam or firefighting foam were not considered, because these were not representative of the method used and the cause of death was different (i.e. suffocation rather than anoxia), which may have different implications in terms of animal welfare, as in water‐based foam, the means of death is reported to be occlusion of the trachea (Korenyi‐Both et al., 2022). Any method designed to cause occlusion of the trachea would be equivalent to death by drowning or suffocation, which is not recognised as humane killing method in Council Regulation (EC) No 1099/2009 on the protection of animals at the time of killing.…”

Unreactive N2 (Nitrogen gas) or the Reactive Toxic but Potent Anesthetic H2S (Hydrogen Sulfide gas) for More Humane Prisoner Executions and Animal Euthanasia? More Lessons, and Questions, from Anesthesia

“…(Recently reviewed by Arruda AG et al 62 ) Expansion gas-infused foams have been investigated. 63,64,65,66 A study by Lorbach et al 67 found that CO2 took an average of 202 sec for swine to stop moving -considerable better than N2 but not without its own issues.…”