Assessing the welfare of laboratory mice in their home environment using animal-based measures--a benchmarking tool

Welfare problems in laboratory mice can be a consequence of an ongoing experiment, or a characteristic of a particular genetic line, but in some cases, such as breeding animals, they are most likely to be a result of the design and management of the home cage. Assessment of the home cage environment is commonly performed using resource-based measures, like access to nesting material. However, animal-based measures (related to the health status and behaviour of the animals) can be used to assess the current welfare of animals regardless of the inputs applied (i.e. the resources or management). The aim of this study was to design a protocol for assessing the welfare of laboratory mice using only animal-based measures. The protocol, to be used as a benchmarking tool, assesses mouse welfare in the home cage and does not contain parameters related to experimental situations. It is based on parameters corresponding to the 12 welfare criteria established by the Welfare Quality® project. Selection of animal-based measures was performed by scanning existing published, web-based and informal protocols, and by choosing parameters that matched these criteria, were feasible in practice and, if possible, were already validated indicators of mouse welfare. The parameters should identify possible animal welfare problems and enable assessment directly in an animal room during cage cleaning procedures, without the need for extra equipment. Thermal comfort behaviours and positive emotional states are areas where more research is needed to find valid, reliable and feasible animal-based measures.