ARS | Publication request: Gas alternatives to carbon dioxide for euthanasia: A piglet perspective

Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2012
Publication Date: March 1, 2013
Citation: Lay Jr, D.C., Rault, J., Mcmunn, K.A., Marchant Forde, J.N. 2013. Gas alternatives to carbon dioxide for euthanasia: A piglet perspective. Journal of Animal Science. 91:1-10.

Technical Abstract: The identification and validation of a humane method to euthanize piglets is critical to address concern that current methods are not acceptable. This research sought to: 1) identify a method of scientifically determining if pigs find a specific euthanasia method aversive, and 2) develop an innovative method of gas euthanasia. Experiment 1 tested four gas combinations in an approach avoidance test. Pigs were allowed to enter a chamber in which the gases were gradually displacing the air: CO2, (100%); N2O/CO2 (70 %/30%); Ar/CO2 (70%/30%); and N2/CO2(70%/30%). The duration of testing was shortest for the pigs in the CO2 treatment when compared to pigs in Ar/CO2 (P < 0.001), N2O/CO2 (P < 0.01) and the N2 (P < 0.001) treatments, 3.1 ± 0.2; 9.60 ± 0.4; 8.5 ± 0.6; 9.9 ± .1 minutes, respectively. In Experiment, 2 pigs were euthanized using a 2-step procedure using a gradual fill of 1 of 4 gas mixtures (90% CO2, 70% N2/30% CO2, 70% N2O/30% CO2 or 70% N2O/30% O2. When the pig became panicked or anesthetized it was placed into 90% CO2. The CO2 pigs had to be moved into the chamber pre-charged with CO2 sooner (P < 0.001) at 2.9 ± 0.3 minutes, than for the N2/CO2 (6.4 ± 0.6 minutes) N2O/CO2 (6.7 ± 1.0 minutes), and N2O/O2 (14.7 ± 2.1 minutes). All pigs in the N2O/O2 treatment were moved into the CO2 chamber because they became anesthetized. In contrast, none of the pigs in the other treatments became anesthetized and were moved into the CO2 chamber because they either started to squeal or panic. Although death using nitrous oxide took the longest, pigs did not enter a state of panic, thus this treatment was the most humane.