Assessing the humaneness of gas euthanasia techniques for laboratory rodents

Most laboratory rodents are killed with carbon dioxide (CO₂). There is general consensus that CO₂ causes aversion - but disagreement as to how significant this is, nonetheless it has been suggested that CO₂ should be replaced by volatile anaesthetics, e.g. Isoflurane. If CO₂ is to be replaced, it is essential that the replacement is demonstrably more humane. If CO₂ use is to continue, it is imperative that we understand which method of delivery represents best practice. We will answer two key questions: 1) How aversive is CO₂ compared to other methods? We will use a conditioned place avoidance paradigm to compare the relative aversiveness of CO₂ and Isoflurane against known unpleasant stimuli (predator odour, cold etc). 2) Could CO₂ or Isoflurane be applied in a less stressful way? Stress associated with euthanasia may be enhanced by moving animals to a euthanasia chamber. We will examine whether mice could be exposed to CO₂ in a less stressful way by carrying out the process in their home cages whilst relaxed (or sleeping). At the end of the study we will organise a consensus meeting to disseminate results to stakeholders to ensure that any findings contribute as rapidly as possible to improvements in practice.

• Research Review 2013: Improving rodent welfare during euthanasia
• Blog: Laboratory animal euthanasia
• News: Newcastle University to investigate euthanasia of laboratory rodents
• News: Report of the second Newcastle meeting on laboratory animal euthanasia