Guidelines for Assessing the Health and Condition of Mice

Transgenic and knockout technologies have caused a shift in research focus at many institutions. Increased numbers of mice—some with potentially debilitating phenotypes—are being maintained to their natural life spans, and this has challenged the laboratory animal community to devise effective strategies for monitoring and managing these colonies. Aside from meeting essential obligations for ensuring the well-being (freedom from discomfort, distress, and pain) of the research mouse, effective management and supervision of mouse colonies is useful in fulfilling the “3 Rs” (replacement, reduction, refinement) put forth by Russell and Burch 1 . We also suggest a fourth essential “R,” investigator responsibility, since investigators are increasingly monitoring and managing their own transgenic colonies. A well-monitored and -managed rodent colony will provide: more precise information on the progression of disease or phenotype; clear criteria for data collection; recovery of data potentially lost when unmonitored mice die; improved quality, and increased uniformity, of data due to standardized techniques for monitoring health; additional observations and characterization of phenotypes; possible decrease in number of mice needed to characterize a phenotype; and decreased costs of characterizing a phenotype.