THE REFINEMENT REFERENCE CENTER: IMPROVING LABORATORY MICE WELFARE THROUGH ENRICHED CAGE SYTEMS

Mice have been the most commonly used species in animal testing in the European Union for many years (European Comission, 2024). They are protected under EU Directive 2010/63/EU, which requires housing and enrichment that allow the expression of natural behaviour.
However, the minimum cage dimensions defined in the directive are insufficient to ensure adequate welfare. Moreover, the recommended enrichment measures are not legally binding, resulting in minimal enrichment in many facilities. Numerous studies demonstrate that such housing conditions negatively affect mouse health and welfare (Cait et al., 2022; Mieske et al., 2022).
To address these limitations, we propose the “Refinement Reference Center” (RRC), an alternative cage system incorporating low-cost modifications to standard housing. The RRC includes tunnels that connect multiple cages into larger “cage units,” thereby increasing available space and social contacts. These tunnels are equipped with closable gates and RFID antennas, allowing tracking of individual movement and activity. Additionally, each cage unit contains a “play pen cage” offering a regularly changing selection of enrichment tools to provide physical and cognitive stimulation.
We hypothesise that C57BL/6 mice housed in the RRC system will show improved behavioural performance, enhanced organ development, reduced chronic stress, and higher immune competence compared to mice housed in standard housing conditions. In cooperation with the University Hospital Essen, these outcomes will be evaluated through comparative behavioural, physiological, and immunological assessments between RRC-housed mice and control groups maintained under conventional housing conditions.