Mice are the most widely used laboratory animals. Their welfare has improved dramatically through the 3Rs framework, but significant challenges remain in practice.
Laboratory mouse welfare has improved significantly through the 3Rs framework, but substantial welfare challenges remain. Pain from experimental procedures is often inadequately managed because pain assessment in mice was historically poor. The mouse grimace scale, developed from research on facial pain expressions, has enabled better pain recognition and treatment. Social isolation, which was standard for many experiments, causes measurable psychological harm - guidance now recommends social housing as default. The welfare cost of each procedure must be balanced against genuine scientific benefit in a harm-benefit analysis.