Beyond single metrics: Multi-parameter home-cage monitoring improves welfare assessment.

Single outcome measures often fall short of the sensitivity and objectivity expected under European Directive 2010/63, particularly in fast progressing disease models. To address this gap, the German Research Foundation consortium FOR2591 collated data from 55 routinely used models in six species and narrowed more than 50 candidate readouts down to a 15-parameter core panel spanning behaviour, physiology, biochemistry and imaging. Quantitative tools such as the Composite Measure Schemes, the endpointR and the Relative Severity Assessment algorithm fuse these multidimensional streams into more objective severity scores that outperform singular readouts such as body weight change and clinical scoring in detecting early distress and refine humane endpoint decisions. More than 10 external laboratories have already integrated the open-source toolbox, illustrating practical scalability. A consortium survey showed that no single metric is both widely applied and consistently valued, underscoring the need for multi-parameter monitoring. Ongoing Phase III analyses extract model specific digital fingerprints that trigger real-time risk alerts in home-cage systems. By providing a shared yet adaptable framework, FOR2591 charts a feasible path toward Directive 2010/63 compliance, improved model validity and individualized animal care, establishing a path of a more evidence-based severity assessment.