Environmental enrichment for laboratory rats is not merely beneficial but essential for welfare and scientific validity, yet implementation remains highly variable across institutions.
Laboratory rat welfare through enrichment is an area where the science clearly supports comprehensive provision, yet practice lags substantially. Rats deprived of nesting material cannot thermoregulate efficiently, show higher stress, and perform more abnormal behaviors — outcomes that affect both welfare and experimental reliability. Enrichment is not a confound to be minimized but a welfare requirement to be met, with study design adjusted accordingly rather than animals deprived. The argument that enrichment compromises experimental control is increasingly recognized as an inversion of the proper relationship between animal welfare and scientific validity.