LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II ...

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6 LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II6. Caging7. Cage size—miceCages for rats and mice are designed to includethree important characteristics: provide comfortableliving space, protect the occupants from airbornepathogens or chemicals, and be fabricated frommaterials that can be efficiently cleaned andsanitized. Mice are typically housed in plastic“shoebox-size” cages that have solid sides andbottoms, require absorptive bedding, and can beplaced on shelves or suspended from racks. Ratscan be housed in either plastic shoebox or wirecages. Suspended wire caging, preferablyconstructed of stainless steel, separate animals fromtheir excreta. Wire caging provides better ventilationthrough greater air exchange but has limited valuefor preventing airborne exposure to aerosolizedmicrobes or chemicals. Solid bottom cages withbedding are warmer for small animals and providemore protection from airborn contaminants.Floor areas listed in this image are based on bodyweight and illustrate the minimum space requirementsrecommended in the Guide for mice to livecomfortably. The recommended height of 5 in. (12.70cm) allows mice to sit up and make other normalpostural adjustments and excludes space occupied byfeeders built into cage lids (2).8. Social groups—mice A special consideration for housing is that male mice caged togethermay demonstrate aggression and will often fight and mutilate oneanother. When injuries or fighting are noticed during daily healthobservations, aggressors should be removed from the cage andhoused separately to prevent further injury or death to cagemates.9. Cage size—ratsThis image shows the minimum floor spacerequirements for laboratory rats. Currently, the interiorheight of all cages, excluding lid space, is 7 in. (17.78cm) (2). In general, the minimum floor space increaseswith every 100 g increase in body weight over 100 g.10. Spread of diseases Rats and mice are susceptible to a wide range of diseases that can bespread by direct contact, through poor hand washing practices bycaretakers, by contaminated caging or equipment, and by aerosolizedparticles and dust. Diseases introduce unwanted experimentalvariables; thus, procedures, practices, and specialized equipment areutilized to minimize or eliminate the spread of diseases.
V-9042 RATS AND MICE: Care and Management 711. Types of facilities Rats and mice have traditionally been housed in facilities where stableenvironmental temperature, humidity, and lighting are maintained inanimal rooms. The current trend, however, is to enhance these“conventional housing” facilities by the addition of specializedequipment, such as laminar airflow (LAF) hoods, individually ventilatedcaging systems, and cages with air filters built into the lids. Thisequipment increases the level of health protection for the animals bycreating barriers against the entry of pathogens. The “barrier” conceptis taken a step further by the design of buildings that utilize separatecorridors for moving clean and dirty equipment to minimize crosscontamination between work areas. In barrier facilities, supplies arechemically or steam sterilized, and personnel are required to showerand don sterile clothing prior to entry into the building or into animalrooms. The effectiveness of these barrier facilities has been proven intheir frequent utilization for maintaining specific pathogen-free (SPF) orvirus antibody-free (VAF) animals required for support of sophisticatedresearch projects.12. LAF pattern13. Filter bonnetsAnother way to exclude pathogens in bothconventional and barrier facilities is to minimize thedeposition of contaminated dust particles in cages byutilizing a laminar air flow (LAF) system. Air passesthrough High Efficiency Particulate Air (HEPA) filtersand is directed at high velocity in a uniform laminarflow pattern over an individually ventilated cage,through a hood, or across an entire room. Propermanagement procedures must be established andfollowed, however, because the benefits of thesesystems will be compromised if staff members do notpractice good personal hygiene or if equipment is notproperly sanitized.“Shoebox” cages can be equipped with filter covers toprevent microbial contamination by aerosols orfomites. Although there are various types of filterbonnets manufactured, they all limit air and gasexchange, allowing heat, carbon dioxide, moisture,and ammonia to build up within the cage, unless theyare individually ventilated.
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LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II ...

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