A Good Death? Report of the Second Newcastle Meeting on Laboratory Animal Euthanasia

Abstract

Millions of laboratory animals are killed each year worldwide. There is an ethical, and in many countries also a legal, imperative to ensure those deaths cause minimal suffering. However, there is a lack of consensus regarding what methods of killing are humane for many species and stages of development. In 2013, an international group of researchers and stakeholders met at Newcastle University, United Kingdom to discuss the latest research and which methods could currently be considered most humane for the most commonly used laboratory species (mice, rats and zebrafish). They also discussed factors to consider when making decisions about appropriate techniques for particular species and projects, and priorities for further research. This report summarises the research findings and discussions, with recommendations to help inform good practice for humane killing.

Keywords: 3Rs; animal welfare; carbon dioxide; euthanasia; humane killing; mouse; rat; refinement; zebrafish.

Figure 1

Meeting participants’ responses to the questions: “Which methods do you use to kill mice/rats?”.

Figure 2

Meeting participants’ responses to the question: “Which methods do you use to kill fish?”.

Figure 3

Example of apparatus for conditioned place preference/aversion paradigm. The right and left cage compartments have differently patterned and textured floors and walls to ensure the animal can discriminate between them.

Figure 4

The induction of loss of consciousness during 20% per minute filling with CO₂. Time line for loss of consciousness in rats exposed to CO₂ at 20% chamber volume per minute. Animals lose consciousness after approximately 156 s. Bars below the x-axis indicate periods where the animals would be conscious or unconscious. Shaded area shows the likely time/concentration where CO₂ could cause pain (which occurs after loss consciousness in this case). Levels above 5% may cause anxiety and include a significant duration where the animal would still be conscious.