Effect of 2 Bedding Materials on Ammonia Levels in Individually Ventilated Cages

For many animal facilities, IVC are an increasingly popular rodent housing option. These cages offer several benefits over traditional cage systems, including better containment, simplified handling, and increased protection from allergens.9 Disposable IVC systems might also provide labor and cost savings by eliminating the need to clean and sanitize reusable cages. In addition, IVC systems have been shown to reduce cage ammonia levels and extend cage change intervals compared with static cage systems.7 As facilities make changes to IVC systems, the type of bedding to use and cage change frequency are important considerations. In accordance with the Guide for the Care and Use of Laboratory Animals,10 bedding must be replaced and the microenvironment cleaned often enough to keep animals clean and dry and to keep pollutants (for example, ammonia) below irritating levels.10 Due to a lack of directly comparable published data on this topic, conflicting advertising by bedding and IVC manufacturers, and marked differences in design and performance among IVC systems, choosing the right bedding and cage-change interval can be difficult.3 Although high bedding absorbency is often associated with its ability to better neutralize ammonia, this situation is not always the case, and few published data are available to support these claims.13 The absorbencies of some bedding types have been measured, but results vary greatly depending on whether absorbency is measured relative to the mass or the volume of bedding.2 In the current study, we sought to compare the accumulation of intracage ammonia between IVCs using 1/4-in. of corncob or an α-cellulose paper bedding in a commercially available IVC system for 21 d. Corncob and α-cellulose beddings were selected for this study because they are available in prefilled disposable cages directly from the IVC rack manufacturer. This study sought to identify the optimal bedding choice and cage-change interval for use in the IVC system in our vivarium. Similar studies have been performed by using various types of bedding and cage systems but report inconsistent results. Two studies report significant accumulation of intracage ammonia in IVC after only 1 wk when using recycled paper bedding,12,15 whereas another reports no measureable intracage ammonia after 2 wk when a similar bedding was used.7 In addition, many bedding and cage combinations have not been tested in IVC systems. It is important to note that the manufacturer of the α-cellulose paper bedding claims significant performance differences between recycled paper beddings and those of engineered α-cellulose paper.14