Housing of Rodents Guidelines
Policy No: 107.17
Revision: 1
Effective Date: 9/23/2008 (revised 03/25/14)
Category: Research Guidelines
PURPOSE:
This guideline describes the standards and responsibilities for maintaining adequate population
densities of rodents.
INTRODUCTION:
Rodents must be maintained in accordance with the recommended space for commonly used
group-housed laboratory rodents (NRC, 2011), unless specifically exempted by the IACUC.
Overcrowding is detrimental to the health and wellbeing of the animals and in violation of
published housing standards. When overcrowded cages are observed the animals must be
separated promptly.
Overcrowding of cages commonly occurs in breeding protocols when animals are not weaned or
separated in a timely fashion or when animals grow over time exceeding their recommended
space.
ANIMAL HOUSING RESPONSIBILITIES:
Non-compliance with space requirements is not allowed by our accreditation standards and is
not consistent with the welfare of the animals.
1. Investigators and their research technicians are responsible for monitoring and maintaining
acceptable numbers of rodents per cage. Rodents, which exceed cage space guidelines due to
excess number and/or growth or gain in body weight, must be separated.
2. Animal caretakers should evaluate the cage density conditions when they perform their daily
animal observations or husbandry activities. They should identify any overcrowded cages and
notify the veterinary technician. Animal caretakers are not authorized to separate animals
without specific authorization from the investigator or LAS supervisor.
3. Veterinary technicians are responsible for identifying overcrowded cage conditions during
their regular animal health examinations and clinical rounds of the facility. They are to identify
each overcrowded cage with an overcrowded tag. Veterinary technicians will notify the
responsible investigator for action. These notices are to be dated when placed on the cage and
not removed until the condition is corrected.
4. Veterinary technicians may be authorized by the clinical veterinarian to separate animals
unilaterally under certain circumstances and charge the cost of the labor to the principal
investigator. The clinical veterinarian and/or the IACUC will handle incidents of non-compliance
with these standards by investigators.
5. Investigators who regularly avoid taking care of their overcrowded cages will be reported to
the IACUC and directed to comply with this policy. Possible outcomes for noncompliance may
be suspension of the right to perform animal research studies at TJU and increased charges for
separating the cages. The Laboratory Animal Services staff is not responsible to regularly
separate animals in overcrowded cages, especially in breeding colonies.
HOUSING STANDARDS:
Rodents must be group housed whenever possible, unless an exception is granted by the
IACUC or the Clinical Veterinarian. This exception will only be granted in response to a scientific
justification or health related issue. Some exceptions are listed below.
Please note that group housing must comply with the space recommendations for rodents. For
the latest standards, please consult University Veterinarian Office at Jefferson Laboratory
Animal Services.
EXCEPTIONS
The following conditions are exceptions to this rule.
1. Breeder males should be single housed to prevent fighting, injury and death. Unrelated males
(animals from different litters) should not be combined in cages after they have reached sexual
maturity.
2. Animals that are debilitated from surgery or other experimental procedures may be single
housed until they have fully recovered.
3. Incompatible social groups or improper mixing of sexes or age groups may require special
groupings.
4. Single housing is permissible in cases where only a single animal exists.
5. Animals may be singly housed if there is a justified scientific reason for such, or at the
discretion of the Clinical Veterinarian due to animal health related issues.
It is recommended that singly house animals be provided other forms of enrichment to
compensate for the absence of other animals, such as safe and positive interaction with the
care staff and enrichment of the structural environment. The IACUC or Clinical Veterinarian
must approve this alternate form of enrichment.
REFERENCES
National Research Council of the National Academies (NRC). (2011). Guide for the care and
use of laboratory animals (8th ed.). Washington, DC: National Academies Press.