Assessing the Humaneness of Gas Euthansia Techniques for Laboratory Rodents

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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:
o 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).
o 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