The welfare needs of laboratory rats and the evidence that better welfare produces better scientific data.
Laboratory rat welfare improvements are justified on both ethical and scientific grounds. The scientific case is now well-established: rats housed in chronically stressful, barren conditions have altered baseline physiology that confounds experimental results. The variability introduced by stress-induced immune changes, neurochemical alterations, and behavioral suppression makes individual animals less reliable experimental subjects and requires larger sample sizes to achieve statistical power. Every improvement in rat welfare — social housing, enrichment, positive human interaction, reduced handling stress — simultaneously reduces suffering and improves the scientific value of each animal used. This is a rare case where ethics and efficiency are genuinely aligned.