Javier Guillén, Sarah Wolfensohn
Research animal facilities are often perceived as the defining element of high-quality animal care and use; however, international standards and accreditation practices increasingly emphasize that the animal care and use program (ACUP), rather than the physical infrastructure, is the central determinant of animal welfare, scientific quality, and ethical and legal oversight. This paper examines the relationship between the animal facility and a robust ACUP, arguing that the facility should be understood primarily as an enabling component of a broader institutional system. There is no universal 'ideal' facility design. Instead, infrastructure must be fit for purpose, reflecting the species housed, the nature of the research, institutional scale, available expertise, and staffing. A performance-based approach provides the most appropriate framework for evaluating facility adequacy, focusing on measurable welfare and operational outcomes rather than prescriptive engineering standards alone. The facility should actively support the implementation of the 3Rs (Replacement, Refinement, and Reduction) and the culture of care, promote operational efficiency, and incorporate principles of environmental and financial sustainability. Continual evaluation and improvement are essential to ensure that facilities and ACUPs evolve alongside animal, scientific, and institutional needs. General observations commonly made during AAALAC International accreditation site visits further illustrate how programmatic strength can compensate for infrastructure limitations, while well-designed facilities cannot substitute for weak governance or oversight. Ultimately, excellence in research animal care arises from the alignment of infrastructure, institutional culture of care, ethical responsibility, and programmatic management, with the facility serving as a flexible tool that supports, rather than defines, a high-quality animal care and use program.