LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II ...

V-9042 RATS AND MICE: Care and Management 917. BeddingThis image illustrates a variety of bedding materialsused in lab animal facilities. Solid bottom cagesrequire the use of absorbent bedding to maintain acomfortable dry environment. Absorbent beddingoffers rats and mice the opportunity to make nestsand provides hiding places. Commercially availablecontact bedding includes a variety of absorptivematerials: hardwood chips, hardwood and softwoodshavings, processed peanut hulls, and pelletedcorncobs. Noncontact bedding, usually placed in pansunder suspended wire cages, includes: cageboard (acardboard material), multilayered absorptive cellulosepaper, or any of the contact bedding listed above.18. Complications Various types of bedding have occasionally been associated withrespiratory, digestive, skin, trauma, and biochemical complications. Forexample, aromatic hydrocarbons given off by softwood shavings, suchas cedar chips or pine bedding, can affect liver enzymes, therebyaltering an animal’s response to anesthesia or its metabolism of drugsor test agents. Contamination of natural product bedding withpesticides, herbicides, or other chemical contaminants prior toprocessing may introduce an unwanted variable into toxicity studies,necessitating analysis of the bedding prior to use. Exceptionally dustybedding can cause respiratory problems in humans and animals, andairborne particles can facilitate transport of microbial agents.19. Ammonia contaminationThis graphic demonstrates a complication associatedwith a plastic cage and absorbent bedding—thebuildup of ammonia. Urine in bedding can be brokendown by urease bacteria to produce ammonia. At highconcentrations ammonia can impede or eliminate thefunction of the mucociliary apparatus in the lowerrespiratory passages and predispose animals torespiratory disease. The respiratory tracts of rats andmice are adversely affected at 5 ppm, while thehuman nose cannot detect ammonia until it reacheslevels of 25 ppm. Frequent bedding changes andadequate ventilation of rooms and cages shouldminimize ammonia buildup. Since filter tops on cagesminimize air exchange, there is an increasedrequirement for cleanliness and adequate ventilationwhen using them.