Welfare indicators are the scientific tools used to assess animal wellbeing, and choosing appropriate measures determines the quality of welfare outcomes.
The quality of animal welfare depends fundamentally on what we measure. Input-based standards — stocking density, cage size, equipment type — are easy to audit but may not reflect actual welfare outcomes. An animal in a larger cage that is still barren, isolated, and frightened is not necessarily better off than the density figure suggests. Outcome-based indicators — assessed directly from the animal using validated tools — provide more honest pictures of welfare quality. The shift toward measuring behavioral, physiological, and health outcomes from individual animals reflects a maturing welfare science that is increasingly focused on what animals actually experience rather than what their physical environment looks like on paper.