Rodents (1996) / Chapter Skim
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5 HUSBANDRY
5 HUSBANDRY
Pages 44-84
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From page 44... ...
Those used to house rodents should have the following features: · They should accommodate the normal physiologic and behavioral needs of the animals, including maintenance of body temperature, normal movement and postural adjustments, urination and defecation, and, when indicated, reproduction. · They should facilitate the ability of the animal to remain clean and dry.
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From page 45... ...
Opaque plastic or metal cages might provide a more desirable environment for some studies or breeding programs; however, adequate inspection of animals will usually require manipulation of each cage. The bottoms of rodent cages can be either solid or wire.
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From page 46... ...
The use of filter tops restricts ventilation and can alter the microenvironment of the rodents housed in the cages; therefore, to maintain a healthful environment, it might be necessary to change the bedding and clean the cages more often (Keller et al., 19891. A cubicle (also called an Illinois cubicle or a cubical containment system)
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From page 47... ...
A number of studies designed to evaluate the effects of space on population dynamics have been conducted on wild and laboratory rodents housed in a laboratory environment (e.g., see Barnett, 1955; Christian and LeMunyan, 1958) , but some of them used caging systems different from those generally used in laboratory animal facilities (e.g., see Davis, 1958; Joasoo and McKenzie, 1976; Thiessen, 1964~.
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From page 48... ...
For the most part, laboratory rodents are social animals and probably benefit from living in compatible groups (Brain and Bention, 1979; NRC, 1978; White, 19901. Although more study is needed, rodents maintained for long periods, as in lifetime studies, appear to survive longer when housed in large, compatible social groups than when housed in small groups or individually (Hughes and Nowak, 1973; Rao, 19901.
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From page 49... ...
Laboratory rodents exhibit some vertical exploratory behavior when put into a new cage, and it has been suggested that relatively high cages be provided to accommodate this occasional behavior (Lawlor, 1990; Scharmann, 1991~. However, there is no good evidence to suggest that rodents require tall enclosures.
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From page 50... ...
Studies in the past generally focused on prolonged exposure of laboratory animals to temperatures above 85°F (29.4°C) or below 40°F (4.4°C)
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From page 51... ...
In the absence of well-controlled studies that used objective measures for determining optimal ranges, recommended temperature ranges for laboratory rodents have been independently developed by several groups on the basis of professional judgment and experience (e.g., CCAC, 1980; Council of Europe, 1990; NRC, 1996 et seq.~. Humidity Relative humidity varies considerably with husbandry and caging practices.
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From page 52... ...
provides optimal ventilation for laboratory rodents. Existing guidelines have been criticized as being based mainly on keeping odors below objectionable limits for humans (Beech, 1980; Runkle, 1964)
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From page 53... ...
toxic or odor-caus~ng gases produced oy aecompos~uon of animal wastes can be removed by the ventilating system with chemical absorption or scrubbing, but those methods might not be completely effective. Frequent bedding changes and cage-cleaning, a reduction in number of animals housed in a room, and a decrease in environmental temperature and humiditv within limits recommended in the Guide (NRC, 1996 et seq.)
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From page 54... ...
The degree to which cages are ventilated by the room air supply is affected by cage design; room air-diffuser type and location; number, size, and type of animals in the cages; presence of filter tops; and location of the cages. For example, cages without filter tops provide better air and heat exchange than those with filter tops, in which ventilation is substantially decreased (Keller et al., 19891.
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From page 55... ...
Spectral Distribution Artificial lighting with white incandescent or fluorescent fixtures is preferred for rodent housing facilities because it provides consistent illumination. The two types of lighting have similar spectra, although incandescent lighting generally has more energy in the red wavelengths and less energy in the blue and ultraviolet (UV)
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From page 56... ...
The actual intensity experienced by a rodent in an animal room is influenced not only by the relative locations of its cage and the room lights, but also by cage material and design. The optimal light intensity required to maintain normal physiology and good health of laboratory rodents is not known.
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From page 57... ...
Sound of uniform frequency and unchanging intensity can cause hearing loss in some rodents (Bock and Saunders, 1977; Burdick et al., 1978; Kelly and Masterton, 1977; Kraak and Hofmann, 1977~. Hamsters, guinea pigs, rats, and mice pass through developmental stages during which they are very susceptible to injury from sound of this type (Kelly and Masterton, 19771.
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From page 58... ...
Providing nutritionally adequate diets is important not only for the rodents' welfare, but also to ensure that experimental results are not biased by unintended or unknown nutritional factors. Providing nutritionally adequate diets for laboratory rodents involves establishing requirements for about 50 essential dietary nutrients, formulating and manufacturing diets with the required nutrient concentrations, and managing numerous factors related to diet quality.
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From page 59... ...
Diets manufactured from natural ingredients can contain low concentrations of contaminants that might have no influence on animal health but could affect experimental results. For example, a lead concentration of 0.5-1 part per million is inherent in naturalingredient rodent diets and is not generally detrimental to animal health; but it could substantially influence the results of toxicology studies designed to evaluate lead-containing test compounds.
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From page 60... ...
Use of this type of diet provides the highest degree of control over dietary nutrient concentrations. However, chemically defined diets are not readily consumed by laboratory rodents, and they are usually too expensive for general use.
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From page 61... ...
Vitamin C in diets stored under these conditions has a shelflike of only 90 days. If a vitamin Ccontaining diet stored for more than 90 days is to be fed to guinea pigs, an appropriate vitamin supplement should be added.
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From page 62... ...
The magnitude of fortification in autoclavable diets is not generally high enough to be toxic to rodents; however, the routine use of autoclavable diets without autoclaving is not recommended, because the increased vitamin concentrations could influence experimental results. The level of sterility required for axenic or microbiologically associated rodents requires that the temperature of the diet be raised above 100°C (212°F)
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From page 63... ...
Pasteurization, rather than sterilization, is used because there is less nutrient loss, and the diets are more readily consumed than are sterilized diets. Laboratory rodent diets also can be decontaminated by ionizing radiation (Coates, 1987; Coates et al., 1969; Ley et al., 1969)
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From page 64... ...
However, the reported data show that ad libitum feeding might not be universally desirable for rodents used in long-term toxicologic or aging studies, and this factor should be a prime consideration when designing such studies. WATER Laboratory rodents should have ad libitum access to fresh, potable, uncontaminated drinking water, which can be provided by using water bottles and drinking tubes or an automatic watering system.
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From page 65... ...
Drinking water of animals used in toxicology experiments, particularly those of long duration, should be periodically assayed for compounds that might influence experimental results, even when exposures are small. Mineral concentrations in water can have a profound influence on experimental results in studies designed to establish dietary mineral requirements for laboratory rodents.
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From page 66... ...
SANITATION Cleaning Adequate sanitation is an integral part of maintaining laboratory rodents. Clean, sanitary conditions limit the presence of adventitious and opportunistic microorganisms, thereby decreasing their potential for compromising rodent health or causing adverse interactions with experimental procedures.
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From page 67... ...
It has been suggested that the effectiveness of sanitation procedures can be assessed by the intensity of animal odors, particularly ammonia; however, this should not be the sole means of assessing cleanliness, because too many variables are involved. Agents used to mask animal odors should not be used in rodent housing facilities; these agents cannot substitute for good sanitation practices, and their use exposes animals to volatile substances that can alter basic physiologic and metabolic processes.
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From page 68... ...
Some laboratory rodents, such as guinea pigs and hamsters, produce urine with high concentrations of proteins and minerals. Their urine often binds aggressively to cage surfaces, which therefore require treatment with acid solutions before washing.
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From page 69... ...
Water bottles, sipper tubes, stoppers, and other small pieces of equipment should be washed with detergents, hot water, and, if appropriate, chemical agents to destroy vegetative forms of microorganisms. This process can be manual, if high-temperature rinse water is not used, or performed with mechanical washing equipment built especially for this purpose or a multiple -~ r ~1 · , .
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From page 70... ...
. The program should include regular inspection of the premises for signs of pests, a monitoring system that uses rodent traps and insectcollection devices to capture pests, and regular evaluation of the integrity and condition of the animal facilities.
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From page 71... ...
Individual animals or croups of animals can also be identified with cage identification cards. ~, If cards are used sufficient information is re quired to identify and characterize the animals in the cage adequately.
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From page 72... ...
Bowls for food and water can be used instead of more conventional feeding and watering devices; but guinea pigs like to nest in such receptacles, and that causes waste and contamination of food. Feeders that have a J shape are best suited to address these concerns and are used most commonly.
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From page 73... ...
Gestation in guinea pigs can range from 59 to 72 days; 63 to 68 days is the average. Gestation length can be affected by several characteristics, including litter size, which is usually one to three pups (McKeown and Macmahon, 1956~.
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From page 74... ...
To avoid hibernation, temperatures should be maintained within ranges specified in the Guide (NRC, 1996 et seq.~. Hamsters, like guinea pigs, are susceptible to antibiotic associated toxicity and enterocolitis.
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From page 75... ...
Commercial rodent diets are usually acceptable for gerbils, provided that they have a low fat content. Because of the gerbils' unique fat metabolism, it is not uncommon for them to develop high blood cholesterol concentrations on diets containing fat at 4 percent or more.
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From page 76... ...
1959. Noise stress in laboratory rodents.
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From page 77... ...
1980. Environmental quality within animal facilities.
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From page 78... ...
1977. Dietary standards for laboratory animals: Report of the Laboratory Animals Centre Diets Advisory Committee.
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From page 79... ...
London: Laboratory Animals Ltd. Kaufman, J
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From page 80... ...
1956. The influence of litter size and litter order on length of gestation and early postnatal growth in guinea pigs.
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From page 81... ...
1980. The quality, treatment, and monitoring of water for laboratory rodents.
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From page 82... ...
1991. Improved housing of mice, rats and guinea pigs: A contribution to the refinement of animal experiments.
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From page 83... ...
1989. Use of cage space by guinea pigs.
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From page 84... ...
1975. Analysis of thermal and ventilation requirements for laboratory animal cage environments.
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