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

Abstract

This study sought to identify an optimal rodent bedding and cage-change interval to establish standard procedures for the IVC in our rodent vivarium. Disposable cages were prefilled with either corncob or α-cellulose bedding and were used to house 2 adult Sprague-Dawley rats (experimental condition) or contained no animals (control). Rats were observed and intracage ammonia levels measured daily for 21 d. Intracage ammonia accumulation became significant by day 8 in experimental cages containing α-cellulose bedding, whereas experimental cages containing corncob bedding did not reach detectable levels of ammonia until day 14. In all 3 experimental cages containing α-cellulose, ammonia exceeded 100 ppm (our maximum acceptable limit) by day 11. Two experimental corncob cages required changing at days 16 and 17, whereas the remaining cage containing corncob bedding lasted the entire 21 d without reaching the 100-ppm ammonia threshold. These data suggests that corncob bedding provides nearly twice the service life of α-cellulose bedding in the IVC system.

Figure 1.

Ammonia measurement through sample port. Pump and ammonia tube are shown, with ammonia tube inserted through the sample port and into the cage, above the wire bar, for ammonia measurement.

Figure 2.

Effect of corncob and α-cellulose bedding on intracage ammonia levels (ppm) in IVC. Intracage ammonia levels were measured once daily for 21 d. Each bedding group contained 3 control cages (without animals) and 3 experimental cages, each of which housed 2 adult rats each. All three experimental cages with α-cellulose bedding had significantly (P < 0.05, 2-tailed t test) higher ammonia levels than the experimental corn cob cages from day 8 to the last day that the α-cellulose cages were used. Once the ammonia level reached 100 ppm, the cage was changed immediately, and subsequent ammonia levels are not shown. All 3 experimental α-cellulose cages exceeded 100 ppm ammonia by day 11. One corncob cage lasted the entire 21 d without reaching the 100-ppm ammonia threshold; however the other 2 corncob cages required changing at days 16 and 17. Although each individual experimental cage is plotted separately, the corncob and α-cellulose control groups are represented by one line each, because all control cages remained at 0 ppm ammonia throughout the experiment.