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

68 GUIdE FOR ThE CARE ANd USE OF LAbORATORy ANIMALScan influence the results. Water can be treated or purified to minimize oreliminate contamination when protocols require highly purified water. Theselection of water treatments should be carefully considered because manyforms of water treatment have the potential to cause physiologic alterations,reduction in water consumption, changes in microflora, or effects onexperimental results (Fidler 1977; Hall et al. 1980; Hermann et al. 1982;Homberger et al. 1993; NRC 1996).Watering devices, such as drinking tubes and automated water deliverysystems, should be checked frequently to ensure appropriate maintenance,cleanliness, and operation. Animals sometimes have to be trained to useautomated watering devices and should be observed regularly until regularusage has been established to prevent dehydration. It is better to replacewater bottles than to refill them, because of the potential for microbiologiccross contamination; if bottles are refilled, care should be taken to returneach bottle to the cage from which it was removed. Automated wateringdistribution systems should be flushed or disinfected regularly. Animalshoused in outdoor facilities may have access to water in addition to thatprovided in watering devices, such as that available in streams or in puddlesafter a heavy rainfall. Care should be taken to ensure that such accessorysources of water do not constitute a hazard, but their availability need notroutinely be prevented. In cold weather, steps should be taken to preventfreezing of outdoor water sources.bedding and Nesting Materials Animal bedding and nesting materials arecontrollable environmental factors that can influence experimental data andimprove animal well-being in most terrestrial species. Bedding is used toabsorb moisture, minimize the growth of microorganisms, and dilute andlimit animals’ contact with excreta, and specific bedding materials havebeen shown to reduce the accumulation of intracage ammonia (Perkinsand Lipman 1995; E. Smith et al. 2004). Various materials are used as bothcontact and noncontact bedding; the desirable characteristics and methodsof evaluating bedding have been described (Gibson et al. 1987; Jones 1977;Kraft 1980; Thigpen et al. 1989; Weichbrod et al. 1986). The veterinarianor facility manager, in consultation with investigators, should select themost appropriate bedding and nesting materials. A number of species, mostnotably rodents, exhibit a clear preference for specific materials (Blom et al.1996; Manser et al. 1997, 1998; Ras et al. 2002), and mice provided withappropriate nesting material build better nests (Hess et al. 2008). Beddingthat enables burrowing is encouraged for some species, such as mice andhamsters.No type of bedding is ideal for all species under all management andexperimental conditions. For example, in nude or hairless mice that lackeyelashes, some forms of paper bedding with fines (i.e., very small particlesfound in certain types of bedding) can result in periorbital abscesses (White