Animal Ethics

Pain and Distress in Laboratory Mice: Improving Refinement

Laboratory mice are the most numerous research animals globally. Improvements in pain recognition, analgesia, and housing have significantly improved their welfare in leading institutions.

Key Facts

Approximately 100 million mice are used in research globally each year
The Mouse Grimace Scale allows rapid, reliable pain assessment from facial expressions
Standard housing in groups of 2-5 reduces stress compared to single housing
Nesting material provision reduces corticosterone levels and improves reproductive performance
Most institutions now have mandatory pain assessment protocols for surgical procedures

Welfare Considerations

A mouse that is post-operatively in pain and not receiving analgesia is both suffering and a worse experimental model — stress responses confound results. Refinement advances therefore align welfare and scientific outcomes. The biggest remaining gap is in non-surgical research where pain and distress may be less visibly obvious but equally significant.

What You Can Do

Support NC3Rs funding for refinement research in laboratory animal science
Advocate for mandatory pain assessment reporting in published animal research
Donate to Animal Welfare Institute campaigns for improved laboratory animal standards
Encourage transparency about animal welfare outcomes in published scientific literature