Analysis of Individually Ventilated Cage (IVC) Microenvironments During 21-d Cage Change Frequency for Mice Using Two Different Bedding Types.

The Guide for the Care and Use of Laboratory Animals provides recommendations on sanitation frequencies for rodent caging equipment; however, it allows for performance standards to be used when extending this frequency for individually ventilated cage (IVC) caging. Our institution wanted to reexamine our current standards of care for mouse IVC caging, which includes a 14-d cage bottom and bedding change as well as the use of corncob bedding. This was driven by desire to reduce the stress to mice associated with cage change, and by recent literature showing a potential improved absorbency and multiple health and welfare benefits of paper pulp cellulose bedding products. Therefore, this study sought to compare the impact of different rodent bedding types (paper pulp cellulose and corncob) on mouse IVC microenvironmental parameters over a 14-d compared with a 21-d cage change frequency. Ammonia levels, temperature, humidity, urine latrine size, and the overall animal condition were assessed throughout the 21-d period. Our data indicate that IVC cage bottom and bedding change can be extended to 21 d for either paper pulp cellulose or corncob bedding based on ammonia levels, temperature, humidity, and the animal's overall condition. However, based on early cage change criteria, more frequent cage changes may be warranted before 21 d in cages with corncob, as there was a significantly increased urine latrine size in cages with corncob bedding compared with paper pulp cellulose bedding.