Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN

A fundamental requirement of biomedical research is the proper identification of research animals. It is essential that the right animal is utilized for procedures and data collection. Laboratory mice and rats can be identified with the following permanent methods: ear tags, ear punch codes, microchip implantation, tail tattoos for adult mice, and toe tattoos for neonates. Temporary methods of dyes and marking pens can also be used for acute studies. This video covers the technical aspects of ear tagging and punching for mice and rats, as well as the benefits of each with respect to the type of research being conducted on the animals. Knowledge of the basic manual restraint techniques for each animal (covered in a separate video) is required for these identification methods to be properly accomplished.

1. Ear punch identification

Ear punch codes have been developed as a quick and inexpensive method to label individual animals. There are three styles of ear punches: the scissor punch, the thumb punch, and the lever punch. The animal's right ear is used for single digits, the left ear for tens, and the middle of the ears for hundreds.

1. Restrain the animal so that the ears are easily accessible. Most mice are ear tagged for individual identification at weaning. This requires gent

When choosing the appropriate identification method, many factors must be deliberated. Each technique has advantages and disadvantages that must be considered in relation to the experimental needs. While the costs must be weighed along with other factors, the ease of the technique and the level of discomfort to the animals should be the primary considerations.^3,4

Ear punching/notching is commonly used in mice and rats because there is little cost, and the procedure is easily done. T

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2. Cover, C.E., Keenan, C.M., and Bettinger, G.E. 1989. Ear tag-induced Staphylococcus infection in mice. Laboratory Animals. 23:229-233.
3. Kitagaki, M., Suwa, T., Yanagi, K., and Shiratori, K. 2003. Auricle chondritis in young ear-tagged Crj:CD(SD)IGS rats. Laboratory Animals. 37:249-253.
4. Kasanen, H.E., Voipio, H.M., Leskinen, H., Luodonpää, M., and Nevalainen, T.O. 2011. Comparison of ear tattoo, ear notch and microtattoo in rats undergoing cardiovascular telemetry. Laboratory Animals. 45:154-159.
5. Dalhborn, K., Bugnon, P., Nevalainen, T., Raspa, M., Verbost, P., and Spangenberg, E. 2013. Report of the Federation of European Laboratory Animal Science Associations Working Group on animal identification. Laboratory Animals. 47:2-11.
6. Waalkes, M.P., Rehm, S., Kasprzak, K.S., et al. 1987. Inflammatory, proliferative, and neoplastic lesions at the site of metallic identification ear tags in Wistar [Crl:(WI)BR] rats. Cancer Research. 47:2445-2450.