Laboratory animal facility managers must ensure that animal experiments can be carried out under optimal scientific conditions, that all legal requirements are met, and that animal welfare is maximized. Animal experimentation is stressful not only for the animals involved but also for the people who maintain these animals or carry out the experiments. Many of those involved find themselves in a constant conflict between scientific necessity, care, and harm. Under the term Culture of Care, procedures have been developed to reduce the burden of animal experimentation on the animals and the staff involved. The focus here is on what laboratory animal facility managers can do to improve the welfare of laboratory animals and the people working with them. Exemplary measures are the improvement of the housing conditions of laboratory animals, the introduction of uniform handling measures, clear and transparent structures via a quality management system, implementation of a no-blame culture of error (e.g., via Critical Incident Reporting System in Laboratory Animal Science [CIRS-LAS]), and open and respectful communication with all parties involved in animal experimentation, including the public and representatives of the authorities (public webpage, open house policy). The 6 Rs must be considered at all times: replacement, reduction, refinement, respect, responsibility, and reproducibility. We are writing this article from the perspective of laboratory animal facility managers in Germany.

Health monitoring of aged animal cohorts is challenging, and validated health assessment systems are rare. In this study, we developed a live score for aged laboratory mice based on external symptoms and applied it to untreated mice of advanced age (18–40 months) from three different C57BL/6-background strains. We then validated this system against necropsy findings obtained from the same mice to distinguish external symptoms that accurately predict internal pathologies from those that merely represent by-products of normal ageing without relevance to animal well-being. Live and necropsy score values showed a strong positive association, indicating that the live score reflects internal disease burden with reasonable accuracy overall. Abdominal palpable masses, a body condition score of 2, severe neurological/motoric symptoms and abnormal posture or gait showed the highest predictive value for high necropsy scores. Abdominal palpable masses identified internal tumours >1 cm with high accuracy but showed low sensitivity for smaller tumours. In contrast, frequently occurring symptoms such as impaired fur or skin appearance and mild neurological or motoric impairments showed no apparent association with internal pathologies. Based on these results, we propose a standardized and feasible examination scheme for routine monitoring of aged mice. This data-driven framework supports objective humane endpoint decisions and is likely to improve the detection of clinically relevant diseases, particularly tumours, while acknowledging the limitations of early-stage tumour detection.