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Nitrous Oxide for Piglet Euthanasia

24 February 2015

A study at the University of Melbourne in Australia has demonstrated that 90 per cent nitrous oxide in air can effectively euthanise piglets.

Also from the study – reported by Pork Checkoff in the US – Dr Jean Loup Rault in Melbourne commented that piglets did not find exposure to nitrous oxide aversive although, at high concentrations, the lack of oxygen caused laboured breathing. He added that carbon dioxide more often resulted in flailing behaviour.

This research sought to:

  1. evaluate the piglet’s aversion to inhaling nitrous oxide and oxygen
  2. use electroencephalogram (EEG) to validate the effectiveness and humaneness of nitrous oxide to induce loss of consciousness.

Three experiments were conducted to evaluate different gas mixtures, involving combinations of air, oxygen, nitrous oxide and carbon dioxide to euthanise piglets.

The first experiment allowed piglets to walk freely between one chamber filled with air or another pre-filled with 60 per cent or 90 per cent nitrous oxide.

The next experiment used the same test except the chamber held nitrous oxide pre-filled at 25, 50 or 75 per cent concentration in air or carbon dioxide pre-filled at seven, 14 or 21 per cent concentration in air.

The last experiment used EEG to measure brain activity to assess loss of consciousness as the pigs were subjected to 60 or 90 per cent nitrous oxide or 90 per cent carbon dioxide.

The results demonstrated differences between the three treatments in terms of effects on the brain.

The EEG data strengthen the link between the behavioral results and animal welfare implications that nitrous oxide is less averse than carbon dioxide, although taking slightly longer to take effect.

February 2015

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