A Two-Step Process of Nitrous Oxide before Carbon Dioxide for Humanely Euthanizing Piglets: On-Farm Trials

摘要

Current methods of euthanizing piglets are raising animal welfare concerns. Our experiment used a novel two-step euthanasia method, using nitrous oxide (N 2 O) for six minutes and then carbon dioxide (CO 2 ) on compromised 0- to 7-day-old piglets. A commercial euthanasia chamber was modified to deliver two euthanasia treatments: the two-step method using N 2 O then CO 2 (N 2 O treatment) or only CO 2 (CO 2 treatment). In Experiment 1, 18 piglets were individually euthanized. In Experiment 2, 18 groups of four to six piglets were euthanized. In the N 2 O treatment, piglets lost posture, indicating the onset of losing consciousness, before going into CO 2 where they showed heavy breathing and open-mouth breathing; whereas piglets in the CO 2 treatment did not lose posture until after exhibiting these behaviors ( p ≤ 0.004). However, piglets in the N 2 O treatment took longer to lose posture compared to the CO 2 treatment ( p 0.001). Piglets in the N 2 O treatment displayed more behavioral signs of stress and aversion: squeals/minute ( p = 0.004), escape attempts per pig ( p = 0.021), and righting responses per pig ( p = 0.084) in a group setting. In these regards, it cannot be concluded that euthanizing piglets for 6 min with N 2 O and then CO 2 is more humane than euthanizing with CO 2 alone.