A Practical Approach, Second Edition=Ronald D. Ho.pdf

DEVELOPMENTAL TOXICITY TESTING — METHODOLOGY 213Table 7.4Recommended parameters for caging and environment for common laboratory animalsBody Cage Floor Area Cage Height Relative Dry-Bulb TemperatureAnimal Weight in. 2 cm 2 in. cm Humidity (%)°C °FMouse 15–25 g 12.0 77.42 5 12.70 30–70 18–26 64–79>25 g >15.0 96.78 5 12.70Rat 500 g >70.0 451.64 7 17.78ft 2 m 2Rabbit < 2 kg 1.5 0.14 14 35.56 30–70 16–21 61–722–4 kg 3.0 0.28 14 35.564–5.4 kg 4.0 0.37 14 35.56>5.4 kg >5.0 0.46 14 35.56Source: Data from National Research Council, Guide for the Care and Use of Laboratory Animals, Institute ofLaboratory Animal Resources, Commission on Life Sciences, National Research Council. National AcademyPress, revised 1996, Tables 2.1, 2.2, 2.3, and 2.4.of the liver, spleen, kidneys, gastrointestinal tract (esophagus, stomach, duodenum, jejunum, ileum,cecum, colon, and rectum), lungs, lymph nodes (submaxillary and mesenteric), and reproductiveorgans (testes, epididymides, prostate, seminal vesicles, coagulating gland, vagina, corpus andcervix uteri, oviducts, and ovaries). This adds increased costs to studies and is generally unnecessaryfor the relatively short-term developmental toxicity studies if a reputable vendor is used. (For longerterm studies, such as multigeneration, Phase I or III studies, this procedure is recommended.)C. Animal Husbandry1. Housing, Food, and WaterAnimals should be singly housed (except during quarantine or mating for rodents) so that foodconsumption can be determined (as required by testing guidelines) and so that there will be noconfounding factors from group dynamics. For example, a dominant female rat or mouse will eatmore than others, a dominant female mouse may overgroom (to the point of “barbering”) othercohabited mice, and stress levels of variously ranked females may vary, with consequences unrelatedto chemical exposure.Rodents can be housed in solid-bottom polycarbonate or polyethylene cages with stainless-steelwire lids (e.g., from Laboratory Products, Rochelle Park, NJ), using hardwood or other wellcharacterizedbedding (see below). Alternatively, they can be maintained in stainless-steel, wiremeshcages mounted in steel racks, with Deotized ® paperboard (e.g., from Shepherd SpecialtyPapers, Inc., Kalamazoo, MI) placed under each row of cages to collect solid and liquid excreta(copulation plugs for rats will also be detectable on the paperboard if the animals are individuallyhoused in hanging cages). Rabbits are housed in stainless-steel cages with mesh flooring (e.g., fromHoeltge, Inc., Cincinnati, OH), with a pan lined with paperboard beneath each cage to collectexcreta. The dimensions of the cages as required by the NRC Guide 31 (update of the NIH Guide 32 )are presented in Table 7.4, by species and body weight range.Feed must be certified and analyzed (usually by the supplier) and is usually available ad libitumthroughout the study (after any initial adjustments in food presentation for rabbits; see previoussection on quarantine). For rodents, feed can be pelleted and available on the cage lid or in feeders© 2006 by Taylor & Francis Group, LLC