The laboratory animal environment is designed to optimize animal well-being and minimize animal stress.  In addition, an animal facility must conform to regulations, decrease occupational hazards, and be easy to operate. 

The typical laboratory animal lives in three different areas: Megaenvironment-   the animal facility Macroenvironment-  the animal room Microenvironment-   the animal cage

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The megaenvironment is the general layout of the facility.  There are often several species of animals housed in a facility.  Each species of animal should be maintained in a separate room.  Newly arrived animals should be placed in a quarantine area.  Animals on experiment should be housed in animal rooms separate from the breeding colony, other animals, and the laboratories in which experimental procedures are performed.

Support  for the animal rooms should be located near the animals.  Cage cleaning areas can include cage washers,  sterilizing equipment and storage for cleaned cages.  Storage must also be available for food and bedding, with a separate storeroom for wastes and animal cadavers.  A housekeeping room should be included in the facility to store mops, buckets, and cleaning chemicals.

Many different types of laboratories may be present in a research facility.  To decrease stress on animals in their "home" room, experimental procedures should be performed in a separate lab.  A surgical suite must be separate from other areas and should include animal and human prep areas, the surgery room itself, and a recovery/ICU area. A treatment room and diagnostic lab may be present.  

Administrative and personnel areas must be present within the research facility.  This includes offices, meeting rooms, a break room, lockers, shower and bathroom.

Planning of animal facilities requires input from many groups.  Professional engineers and architects with experience in the design of research facilities know the "state-of-the-art" characteristics of effective working labs.  They know the regulatory standards and the construction methods and materials that meet these standards.  Representative users, including the laboratory animal technicians, should be consulted during the planning process.

Facility planning should be made with common-sense decisions and be based on the type and duration of the research to be performed.  It is essential to know the species and characteristics of the animals that are being used, including any hazards associated with the animals and / or the experiment. 

The macroenvironment is the individual animal room.  HVAC, lighting, power and noise control are essential characteristics of animal rooms.  HVAC (heating, ventilation and air-conditioning) supplies oxygen, adds or removes heat, dilutes contaminants, and produces air movement. 

Most species require an air temperature of 60 - 80° F and 45 - 55% relative humidity.  It is important to determine the exact requirements for the animals at your facility; ferrets, for example, do best at a temperature of 45 - 50° F .

The air in an animal room should be completely replaced ten to fifteen times per hour.  Drafts, however, should not be created during these air changes.  The direction in which air moves can be utilized to minimize contamination.  Air always flows from positive to negative.  Negative air flow occurs when air pressure in an animal room is negative compared to the surrounding rooms.  Air will flow into a room with negative pressure, containing odors and potential pathogens within the room.  This is the type of air flow needed in rooms using zoonotic organisms and housing primates.  Positive air flow occurs when the air pressure in the room is higher than the surrounding rooms.  Air will flow from the animal room into the surrounding rooms, preventing contamination of the animal room.  This type of air flow is required in surgery and with germ-free animals. 
                                     

Genetically engineered (transgenic) and immune deficient  animals are usually housed in a laminar flow caging unit.  These units provide uniform continuous positive air flow and HEPA (high efficiency particulate air) filtration, which filter outs up to 99.99% of particles that are 0.3 mm (0.0003 mm) or larger.  Laminar flow systems can also be used with negative air flow to contain highly contagious pathogens and decrease animal allergens.  Static microisolator caging systems move air across the top of cages set on the cage rack.  Recently, ventilated microisolator cage systems have been developed that circulate the air through the cages.

Germ-free animals are typically housed in flexible film isolators.  These create an axenic (totally free of microbes) environment to provide protection for the animals within the isolator.  

The amount, duration and wavelength of light should be appropriate for the species of animal in use.  The Guide for the Care and Use of Laboratory Animals recommends 325 lux (30 ft-candles) for albino animals, because they are prone to light-induced retinal damage.  The photoperiod (length of light and dark periods) is critical for many species, especially breeding animals, and should be controlled by timers for 12 to 14 hours of light per day.

Noise is present throughout animal facilities: barking dogs, squealing pigs and cage washing machinery all produce high levels of sound.  Concrete walls and double doors should separate these areas from other parts of the research facility.  Loud noises are stressful for many species of animals, especially gerbils and strains of mice which are prone to audiogenic seizures. 

The microenvironment is the animal's cage or primary enclosure.  It must contain the animal comfortably and safely, be affordable, meet the needs of the experiment, and meet  government standards.

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The animal cage varies with the species and the experiment.   These parameters must be determined before selection of the caging system!

The size of a primary enclosure depends upon many factors, including:

The Guide for the Care and Use of Laboratory Animals and the standards of the Animal Welfare Act detail minimum cage sizes and characteristics. 

An animal must have at least enough space to turn around, stand up, lie down and perform other normal postures.  Most cages are measured by floor area, length and height.  Floor space does not include areas occupied by food and water bowls or litter pans (unless the cat is using its litter pan as living space).  

Cages may utilize direct bedding (the animals are in direct contact with the bedding) or indirect bedding (animals are on a grate above the bedding).  Direct bedding is important for small rodents that are burrowers by nature.  For these animals, however, it is important that the bedding be nonnutritive, nontoxic, absorbent and comfortable.  Pressed paper, corncobs and hardwood (aspen) chips and shavings are typical beddings.  Caution must be used with animals housed in cages with grates:  the spaces must be small enough so that feet or legs don't get caught or broken and the wires must be thick enough so that foot ulcerations (pododermatitis) don't develop.  Paper pads, newspapers, shavings and corncobs can be used as indirect bedding.  

Resinous wood shavings, especially cedar, are not suitable for use as laboratory animal bedding.  The oils from these shavings interfere with respiration, fertility and liver function.  Pine should be avoided for the same reason, although they are not as toxic as cedar.

Different types of cages can be used for different functions, including general housing, breeding, metabolism (collection of specimens), transport and restraint.

Rodents are generally housed in "shoebox" cages.  These are solid bottomed plastic (or less commonly stainless steel) cages that have a stainless steel lid or that slide into a cage rack like a drawer into a cabinet.  Access into the cage is from the top.  Microisolator cages are "improved" shoe boxes with a polyester fiber filter top that limits movement of pathogens into or out of the cages.  It is important to be aware, however, that the filter also traps heat, moisture and ammonia within the cage, and it is necessary to adjust macroclimate settings and cleaning schedules.

Front-opening cages are used for larger animals, including rabbits, dogs and cats, and nonhuman primates.  The cages may have solid bottoms or floor grates. 

Many animals are grouped housed to enhance the social aspect of their lives and to simplify cage cleaning.  Dogs, cats, rodents, rabbits, sheep, and primates can be put in large cages or runs.

Shoebox cages for rodents are typically made of plastic.  Several types of plastic are used in laboratory animal cages.  

Polypropylene cages withstand normal wash temperatures.  They are opaque, which is desirable for solitary animals that do not need visual stimulation or interaction.  However, the cage must be moved to observe the animals inside, and this may be stressful for them.  Polypropylene cages are more shatter resistant than the other plastics.

Polycarbonate cages are transparent, which is very helpful for animal observation.  With direct bedding, the animals can move away from visual contact with other animals and people, decreasing their stress.  These cages withstand high wash temperatures, can be autoclaved (heat sterilized) and have high impact strength.  

Polyphthalate (or high temperature polycarbonate) cages are more expensive than popypropylene or polycarbonate cages, but can withstand higher sterilization temperatures and more sterilization cycles. It has good impact strength.

Polyphenyl-polysulfone cages are very expensive, but withstand the highest temperatures and can be sterilized over 1000 times.  It has only fair impact strength.

Both polyphthalate and polyphenyl-polysulfone cages are transparent.

Some shoeboxes and most larger animal cages are made of metal.  Stainless steel is preferred because it is very durable and does not rust or corrode.  It is the most expensive caging material.  Aluminum can also be used for metal cages.  It is lighter than steel and less expensive.  It is also, however, less durable.

Wood, iron and zinc-coated galvanized steel are unacceptable for laboratory animal caging.  Wood and iron are difficult to sanitize and the toxic zinc coating on the galvanized metal may be ingested by the animals.

Food hoppers and bowls must be appropriate for the type of food being fed to an animal.  The container least likely to be contaminated should be selected.  Many animals, including rodents and horses, will defecate and urinate in open food and water bowls and buckets.  You must ensure that the animals can reach the food--mice may starve in an 8" deep shoebox with food in a cage-top hopper.  Some animals are entertained by searching for food, such as a dog's  Kong toy stuffed with peanut butter and carpeted foraging boards for primates to pick through to discover seeds. 

Water can be supplied in open bowls, water bottles with stainless steel sipper tubes or an automatic watering system, with water piped into each cage.  Regardless of the method of supplying water, it is essential that the water be fresh and clean and readily accessible.  Some animals, such as dogs and birds, must be taught to use sipper tubes.  

Cats require raised resting platform in their cages.  Platforms are also desirable for other species, such as chinchillas, primates and ferrets. 

Litter boxes must be available for cats, and can be provided for animals such as ferrets and rabbits can be trained to use litter. 

Enrichment devises that improve the well-being of the animals and provide them with shelter and entertainment are often used.  Many devices involve the use of food.  Other items for enrichment include PVC and cardboard pipes for hiding, sheets of bedding that the animals can shred, chew toys and catnip.  Rabbits, cats and other animals can be provided with boxes for shelter and play.

Remember that available floor space for animals is the area that they live in.  If a cat only uses its litter box for defecation and urination, it must not be included in its floor space.  If, however, it sleeps in the litter box, it can be included in the calculations.  Resting platforms, hide boxes and tunnels are considered floor space;  food and water bowls resting on the floor are not.

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