Mouse Cage/Identification Policies

DLAR Policy for The Maximum Number of Mice Housed Per Cage

The ILAR Guide for the Care and Use of Laboratory Animals has guidelines for the maximum number of animals that can be legally housed per cage. Overcrowding of mice is in violation of these guidelines and can jeopardize the University's AAALAC accreditation status.

To assist investigators and DLAR staff in assuring that mice are not overcrowded, the following protocol must be followed:

  1. Standard mouse cages should house no more than four adult mice. Monogamous breeding pairs, or single pregnant females, should be placed in a large mouse breeding cage. Litters should be weaned at approximately 21 days of age. If litters need extended weaning dates, contact Tami Darvin (444-9646).
  2. If a DLAR staff member find cages of mice that are overcrowded, the cage will be labeled and the investigator notified and asked to separate the animals.
  3. The investigator will be given 48 hours to correct the overcrowding problem.
  4. If the overcrowding problem has not been taken care of by the investigator within 48 hours, the DLAR staff will separate the animals and transfer information from the old cage card onto a new cage card. 
  5. If overcrowding is a recurrent problem with an investigator, the animal caretaker will notify their supervisor and/or a DLAR veterinarian.

Permanent Identification of Rodents

Investigators, especially those with rodent breeding colonies within the facility, are reminded of the importance of permanently identifying their animals. Permanent identification will provide protection against mis-identification of animals that may occur due to: 1) phenotypic similarities between animals; 2) weaning of litters and segregation of breeding animals between cages; 3) animals from different investigators housed in the same room; and 4) handling of the animals by a variety of personnel.

The DLAR husbandry staff will place cage cards on rodent cages as the means of primary identification. However, if it is imperative to the research project that rodents be identified, either individually or by group, it will be the research investigators’ responsibility to permanently identify their animals. Possible methods include ear tagging, ear punching, subcutaneous microchip transponders or tail tattooing. It will also be the investigators' responsibility to monitor their colonies to assure that animals are housed, or segregated, by identification number/method, as required, and that the identification (ear tag, ear punch, tattoo) is in place and/or legible.

The DLAR veterinary staff is available (444-2194) to discuss various identification methods and to provide training in identification techniques, if needed.