Burlingame, L. A., Lofgren, J. L. 2014. Presence of nesting material does not prevent ability to accurately identify sick or dead mice during routine health checking. American Association for Laboratory Animal Science [AALAS] Meeting Official Program, 603 (Abstract #P204).

Whether nesting material assists or hinders the ability to identify sick mice during routine health check is a widely debated topic. Currently, our large and diverse academic research institution is exploring the possibility of providing nesting material to all of our mice. In preparing for this change, we conducted an epidemiologic study to evaluate if there was evidence of a disparity in the ability to identify sick or dead mice when nesting material was present or absent in the cage. We hypothesized that provision of nesting material would not result in an inability to identify sick mice and, therefore, would not cause an increased incidence of found dead or severely ill mice. Over a 6-mo period we collected Animal Treatment Reports (ATRs) from 14 rooms, in 5 different animal facilities, balanced across a variety of research and breeding uses either requiring or prohibiting nesting materials. The nesting materials used include nesting squares, crinkled paper strips, cardboard tubes, and cardboard or plastic huts. The data included the clinical condition of the animals on initial veterinary exam and the quality of the nest and nesting material (if present). We also evaluated the death logs from the same rooms to assess the relationship between providing nesting materials and identifying mice that had spontaneously expired in the cage. The data gathered included 800 ATRs and more than 450 death incidences evenly distributed between cages with and without nesting material. The results demonstrate that nesting material does not cause a significant increase in severity of the clinical condition at the time the animal is first reported for veterinary evaluation. Among those cages with nests, there was not a significant difference in clinical condition between the different types of nesting material. Similarly, there was not a significant difference between the number of moribund mice nor numbers of mice found dead in cages under active veterinary monitoring with or without nesting, indicating the ability to identify dying or dead mice is equivalent whether or not nesting material is present. When nesting material was present, significantly more mice were found dead outside the nest rather than in the nest. In summary, nesting material does not hinder the ability to identify sick mice and did not negatively affect the ability to identify mice that expired spontaneously in the cage.