Animal Identification - Preclinical Research Unit

The Preclinical Research Unit (PRU) technicians are proficient at a variety of identification methods in laboratory rodents.

General Guidelines

While there are several acceptable methods of rodent identification, each method has advantages and disadvantages. Long-term studies require a permanent and easily read solution. Some identification methods require specific training and certification by the Office of Animal Care and Use or a certified Laboratory Animal Coordinator.

Ear Tagging

Ear tags are one of the PRU’s preferred methods of identification. They are easily read and can be purchased with a combination of letters and/or numbers printed on them. Ear tags are less suitable for certain study conditions such as the use of high fat foods, strains prone to fighting, and some GEM mice used for cancer modeling.

Ear Notching

Ear notching is an inexpensive and quick method of identifying laboratory rodents. Notching utilizes a hole punch type of tool to identify and provide tissue for genotyping in a single punch. This method is not suitable for pups that are not fully developed or for strains prone to fighting. There are notching charts available for standard identification or a lab can choose to create their own chart.

Tattooing

Tattoos are permanent and easily read. Tattooing is a great alternative to ear tagging, particularly for studies that will utilize the BRIC for imaging. It is more costly than other described methods but is worthwhile for long-term identification of rodents. Tattoos can be more difficult to read in pigmented mice, but UV ink can be used in place of black ink. A modified tattoo procedure on mouse pup toes can be used in place of toe-clipping. Tattoo is charged at a rate of $3.90 per mouse.

Toe Clipping

Toe clipping must be scientifically justified in an approved IACUC application. This method should only be used when no other method is feasible, and the tissue should be used for genotyping purposes as well. Clipping must occur on or before 10 days of age with a maximum of 2 toes per foot.

Short-term Methods

Short-term methods can include a combination of hair clipping and/or permanent marker and fur dyes. These methods will require regular re-application.