BACKGROUND

The Guide for the Care and Use of Laboratory Animals (2011) states "Physical separation of animals by species is recommended to prevent disease transmission and to eliminate anxiety and possible physiologic and behavioral changes due to interspecies conflict." It does acknowledge that it may be possible to house different species within the same room, with proper conditions. 

IACUC Policy

This policy applies to all laboratory animals at Wayne State University. In general, all laboratory animals at Wayne State are separated by species. A small number of different species may be housed in the same room when required and appropriate measures are taken to prevent disease transmission and eliminate the potential for anxiety and physiological and behavioral changes due to interspecies conflict.

Housing different species in the same room may only be permitted if there is need. The need to house animals of different species in the same room can be the result of space limitations, research needs, sentinel requirements, equipment availability, or other reasons approved by the IACUC. Deviations from this policy require IACUC approval.

Rodents

There are currently no diseases that have been detected in mouse or rat populations that place either species at greater risk of interspecies exposure to a pathogenic organism. The literature on housing mice and rats in the same room is limited. In the wild, rats can be predators of mice. Some studies have shown that mice co-housed with rats can exhibit signs of acute and chronic stress, while other studies have found negligible stress-related effects. Given the potential negative impact on animal welfare associated with co-housing, efforts should be made to house mice and rats in separate rooms.

1. Animals must be housed in either ventilated cages or static microisolator cages, each species occupying a separate rack. Rare exceptions will be evaluated on a case-by-case basis. If animals are housed on the same rack, visual barriers should be used between species, where possible.
2. All animal manipulations must be conducted within a Class II biological safety cabinet or equivalent change station as warranted by the situation. 
3. DLAR personnel should only open cages for different species on different days (i.e., mice on Monday, rats on Tuesday), except for emergencies. Additionally, if mice and rats are handled on the same day mice should be handled first.

Farm Animals

Historically, different species of farm animals have been housed in the same pasture and in the same barn, but usually in separate pens. However, mixed species grazing has benefits for both the animals and the environment, co-housing can be used for species enrichment, and guard animals are sometimes helpful to minimize predation. A precedent has therefore been established for housing different agricultural species together. However, in a biomedical research setting it is recommended that mixing of different species of farm animals be kept to a minimum.

1. All domesticated ungulates may be housed in adjacent indoor pens or box stalls, provided animals are free of transmissible disease.
2. When possible, farm animals should be housed with a companion of the same species

References

1. Guide for the Care and Use of Laboratory Animals, National Research Council, 2011.
2. Pritchett-Corning KR, Chang FT, and Festing MF. "Breeding and housing laboratory rats and mice in the same room does not affect the growth or reproduction of either species." JAALAS 48(5), 2009, 492-8.
3. Arndt SS, Lohavech D, van't Klooster J, and Ohl F. "Co-species housing in mice and rats: Effects on physiological and behavioral stress responsivity." Hormones and Behavior, 57(3), 2010, 342-51.

Approved: May 2022