Guide for the Care and Use of Laboratory Animals - Office of ...

ENVIRONMENT, hOUSING, ANd MANAGEMENT4midcage (NASA 1988). Rats and mice generally prefer cages with low lightintensity (Blom et al. 1996), and albino rats prefer areas with a light intensityof less than 25 lux (Schlingmann et al. 1993a). Young mice prefer muchlower illumination than adults (Wax 1977). For animals that have beenshown to be susceptible to phototoxic retinopathy, light should be between130 and 325 lux in the room at cage level.Light intensity decreases with the square of the distance from its source.Thus the location of a cage on a rack affects the intensity of light to whichthe animals within are exposed. Light intensity may differ as much as 80-fold in transparent cages from the top to the bottom of a rack, and differencesup to 20-fold have been recorded within a cage (Schlingmann et al.1993a,b). Management practices, such as rotating cage position relativeto the light source (Greenman et al. 1982) or providing animals with waysto control their own light exposure by behavioral means (e.g., nesting orbedding material adequate for tunneling), can reduce inappropriate lightstimulation. Variable-intensity lights are often used to accommodate theneeds of research protocols, certain animal species, and energy conservation.However, such a system should also provide for the observation andcare of the animals. Caution should be exercised as increases in daytimeroom illumination for maintenance purposes have been shown to changephotoreceptor physiology and can alter circadian regulation (NRC 1996;Reme et al. 1991; Terman et al. 1991).Noise and VibrationNoise produced by animals and animal care activities is inherent in theoperation of an animal facility (Pfaff and Stecker 1976) and noise controlshould be considered in facility design and operation (Pekrul 1991). Assessmentof the potential effects of noise on an animal warrants consideration ofthe intensity, frequency, rapidity of onset, duration, and vibration potentialof the sound and the hearing range, noise exposure history, and sound effectsusceptibility of the species, stock, or strain. Similarly, occupational exposureto animal or animal care practices that generate noise may be of concern forpersonnel and, if of sufficient intensity, may warrant hearing protection.Separation of human and animal areas minimizes disturbances to bothhuman and animal occupants of the facility. Noisy animals, such as dogs,swine, goats, nonhuman primates, and some birds (e.g., zebra finches),should be housed away from quieter animals, such as rodents, rabbits, andcats. Environments should be designed to accommodate animals that makenoise rather than resorting to methods of noise reduction. Exposure to soundlouder than 85 dB can have both auditory and nonauditory effects (Fletcher1976; Peterson 1980)—for example, eosinopenia, increased adrenal glandweights, and reduced fertility in rodents (Geber et al. 1966; Nayfield and