Laboratory mice remain the predominant species used in scientific research. In 2021, approximately 2.1 million mice were used in scientific studies in the UK alone. Given the sheer numbers, an unavoidable consequence of their use is that they must be humanely killed upon completion of the scientific study or at the end of their breeding life. For laboratory mice permitted methods in the United Kingdom consist of exposure to carbon dioxide, concussion of the brain by striking the cranium, overdose of a suitable anaesthetic, or cervical dislocation.

Across the UK, cervical dislocation is the preferred killing method of choice, with 57.5% of participants stating cervical dislocation was their preferred method. Cervical dislocation involves the separation of the vertebrae at the top of the spine and can be achieved manually (i.e., thumb and forefinger) or mechanically (i.e., using a tool or device). However, there is currently no standardised method for achieving consistent cervical separation (in the desired location) and currently there is no dedicated tool specifically designed to achieve accurate and effective dislocation in mice. Instead, research institutions often utilise different methods, either manual or mechanical (and utilise different tools) which have not been validated or assessed for animal welfare impacts. The lack of consistency in the approach poses major animal welfare concerns.

In this project, we aim to identify the preferences of personnel working across UK based research institutions using a short online questionnaire. We will identify the prevalence of manual versus mechanical cervical dislocation, and for those utilising mechanical methods, identify the tools commonly used for both rats and mice. We will then experimentally assess the four most common methods identified from the survey in the target species (mice only for this project) and determine the effectiveness of each respective method in terms of its ability to be both effective and accurate. This will provide the first independent welfare assessment of the most widely used methods for performing cervical dislocation in laboratory mice. This will be achieved by employing sophisticated behavioural (e.g., using high speed videography) and pathological assessment (e.g., CT and/or Xray imaging).