Analysis of IVC Microenvironments During an Extended Cage-Change Interval in Rats (Rattus norvegicus)

Sanitation frequencies for rat caging in the research setting are largely based on recommendations from the Guide for the Care and Use of Laboratory Animals and extrapolated from mouse studies evaluating extended cage-change intervals and different bedding types. This study sought to develop evidence-based recommendations for rat husbandry practices by comparing the impact of paper pulp cellulose (PPC) and corncob (CC) bedding on IVC microenvironments over a 7-, 14-, and 21-day cage-change frequency. Ammonia levels, urine latrine sizes, and overall health of the animals were evaluated over this time. At days 7, 14, and 21 results demonstrate mean ammonia levels of 59.2, 118.4, and 114 ppm for PPC and 7.3, 79.9, and 104.3 ppm for CC as well as average latrine sizes of 2.8, 21.4, and 37.2 cm2 for PPC and 40.5, 185, and 283 cm2 for CC, respectively. A cost-savings analysis compared annual personnel labor costs associated with various cage-change frequencies as well as cost differences in bedding type. This analysis demonstrated that 14- and 21-day intervals and the switch from CC to PPC bedding both provide cost savings benefits.