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Housing and Husbandry for Laboratory Animals

Guidelines for the housing and care of rodents in PSU facilities

 

Housing of Breeding Mice

For permanently paired mice, the number of breeding animals is limited as follows:

  • Shoebox caging (small cages): 1 male and 1 female with litter
  • Gang caging (larger cages): 1 male and 2 females with litters

Alternate configurations involving larger breeder groups may be acceptable if pregnant females are removed prior to giving birth. Breeding cages should be observed by the investigator's staff a minimum of three times a week. Consult the ARP veterinary staff for more information.

The number, age and activity level of mouse pups, as well as the general cage environment, breeding characteristics and/or reproductive performance of the colony may influence decisions on the number of mice to place within a cage. Under certain circumstances, it may be necessary to reduce the cage population or increase the floor space (by moving animals to a larger cage) to ensure the health and welfare of animals. More information on weaning rodents is available on the ARP website.

Breeding colony managers, in consultation with the animal care staff, are responsible for decisions regarding cage space and frequency of cage changes for breeding animals. Investigators who wish to decrease the frequency of cage changes (below normal levels) must first obtain IACUC approval.

Social Housing for Rodents

As social mammals, rats and mice have evolved to co-exist with members of their own species. In fact, appropriate social interactions with conspecifics have been shown to be essential to normal development and well-being. While single housing of laboratory rats or mice is occasionally required, the Guide for the Care and Use of Laboratory Animals (8th ed.) considers group housing the norm. Investigators are expected to pair or group house all rats and mice unless the PSU IACUC has approved specified periods of individual housing as necessary for their experimental protocol.

Investigators must consider the requirements for social housing when planning experiments. Modification of experimental design or procedures to accommodate pair or group housing is frequently possible without affecting data collection and accuracy.

Individual housing is acceptable without specific scientific justification and IACUC approval for the following:

  • When required to prevent injuries and stress associated with aggression (e.g., unfamiliar adult male mice). Housing socially incompatible rodents in the same cage will lead to unrelieved stress and (often) physical injury and pain for those animals; in addition to increased variability as research subjects.
  • During temporary periods associated with breeding activities (e.g., pregnant females housed individually when giving birth). Although commensal nesting is normal for mice and rats, there may be research requirements for temporary single housing.
  • Rarely, when a compatible animal of the same line/status is unavailable. Whenever possible, investigators should plan accordingly to prevent this from occurring.

Environmental Enrichment

Environmental enrichment is intended to facilitate the expression of species typical behaviors and promote psychological well-being. Some form of species appropriate environmental enrichment will be provided to all individually housed rodents unless the IACUC has specifically approved withholding enrichment for experimental reasons. Nesting material is routinely provided to breeding animals. Additional enrichment may be provided at the discretion of the investigative, animal care, and veterinary staff.