Effects of Housing Density and Cage Floor Space on C57BL/6J Mice
Abstract:The Guide for the Care and Use of Laboratory Animals (the Guide) is widely accepted as the housing standard by most Institutional Animal Care and Use Committees. The recommendations are based on best professional judgment rather than experimental data. Current efforts are directed toward replacing these guidelines with data-driven, species-appropriate standards. Our studies were undertaken to determine the optimum housing density for C57BL/6J mice, the most commonly used inbred mouse strain. Four-week-old mice were housed for 8 weeks at four densities (the recommended ∼12 in2 [ca. 77.4 cm2]/mouse down to 5.6 in2[ca. 36.1 cm2]/mouse) in three cage types with various amounts of floor space. Housing density did not affect a variety of physiologic parameters but did affect certain micro-environmental parameters, although these remained within accepted ranges. A second study was undertaken housing C57BL/6J mice with as little as 3.2 in2/mouse (ca. 20.6 cm2). The major effect was elevated ammonia concentrations that exceeded limits acceptable in the workplace at increased housing densities; however, the nasal passages and eyeballs of the mice remained microscopically normal. On the basis of these results, we conclude that C57BL/6J mice as large as 29 g may be housed with 5.6 in2 of floor space per mouse. This area is approximately half the floor space recommended in the Guide. The role of the Guide is to ensure that laboratory animals are well treated and housed in a species-appropriate manner. Our data suggest that current policies could be altered in order to provide the optimal habitation conditions matched to this species' social needs.
Document Type: Research Article
Affiliations: 1: The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, University of Pennsylvania, ULAR/Suite 220, Mail code 3512, 229 S. 40th Street, Philadelphia, Pennsylvania 19104 2: The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609 3: The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609; USGS—Great Lakes Science Center, Lake Superior Biological Station, 2800 Lakeshore Drive, Ashland, Wisconsin 54806 4: Department of Psychology, Brock University, 500 Glenridge Avenue, St. Catherines, Ontario, Canada L2S 3A1
Publication date: December 1, 2004
Comparative Medicine (CM), an international journal of comparative and experimental medicine, is the leading English-language publication in the field and is ranked by the Science Citation Index in the upper third of all scientific journals. The mission of CM is to disseminate high-quality, peer-reviewed information that expands biomedical knowledge and promotes human and animal health through the study of laboratory animal disease, animal models of disease, and basic biologic mechanisms related to disease in people and animals.
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