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Toe-Clipping in Rodents

Case Western Reserve University
Institutional Animal Care and Use Committee
March 2000

The regulations contained in the Guide for the Care and Use of Laboratory Animals stress the importance of proper animal identification in sound research and humane animal care. The Guide, as well as a number of other sources, lists many acceptable identification methods for most common laboratory animal species.

One method of identification that has been used for rodents is toe-clipping. This method involves removal of phalangeal (toe) bones of one toe on one or more limbs. The different digits removed code the identifier.

Because toe-clipping can alter the gait or weight-bearing ability of a rodent's rear limbs, the Guide limits its use to justified instances. According to the 1996 edition, toe-clipping "should be used only when no other individual identification method is feasible and should be performed only on altricial neonates." The IACUC has adopted the following policy in accordance with these guidelines:

• Investigators considering using toe-clipping as a means of rodent identification must first show that they have considered alternative methods of identification.
• The investigator must provide the IACUC with a justification of why toe-clipping is necessary for identification of his or her rodents, including a discussion of why alternative methods are unsatisfactory. For example, a requirement for permanent marking of rodents, and a requirement for early determination of genotype are justifications for toe-clipping.
• Toe-clipping without anesthesia is limited to rodents within the first week of life and must be limited to one digit per extremity.
• A proposal to use toe-clipping in an IACUC protocol must be discussed by the IACUC.