Inconsistency in cervical dislocation: A UK survey of techniques and tools utilised for laboratory rodents

Rodents remain the predominant mammalian species used for biomedical research and must be humanely killed upon completion of the scientific work. Across the UK, cervical dislocation is reported as the most common method for humanely killing laboratory rodents. Cervical dislocation involves the separation of the vertebrae at the top of the spine and can be achieved manually or mechanically (e.g. using a tool). There is no standardised method for achieving consistent cervical dislocation in the desired location, and no dedicated tool specifically designed, validated and commercially available to achieve accurate and effective dislocation. Previous work has highlighted inaccuracy in method application and, as such, has the potential to risk animal welfare at killing. The aim of this work was to identify the techniques used by personnel across UK institutions for performing cervical dislocation using an online questionnaire. We found marked inconsistencies in technique and the use of tools to aid the application. Mice are predominantly killed via manual operation (i.e. without the aid of a tool), while rats are more often killed using mechanical aids. A wide range of improvised tools (i.e. not designed for killing) were reported, including pens, scissors, and cage scrapers. Further, there was little or no consensus regarding which physical actions are essential for a successful dislocation (i.e. a stretch and/or a twist), and a lack of reported institutional standard operating procedures. Further work is needed to establish validated methods and clear standards to ensure this common method is applied humanely and consistently.