Approved: July, 2008
Institutional Animal Care and Use Committee
Toe-clipping is a method for identification of small rodents that involves a numerical scheme in which the distal segment of certain toes is removed with a sharp instrument. It should be used only when no other individual identification method is feasible (such as ear notching, ear tags, tattooing, or subcutaneous implantation of a transponder identification chip). According to The Guide for the Care and Use of Laboratory Animals, "toe-clipping, as a method of identification for small rodents, should be used only when no other individual identification method is feasible and should be performed only on altricial neonates." The Brown University veterinarians have investigated this identification method, and performance of the technique by a competent individual has been observed. The veterinarians consider that toe-clipping, when done skillfully and soon after birth, is not excessively traumatic in and of itself. However, functional compromise does still result from altering the foot and diminishing its tactile, locomotor and weight-supporting utility to the animal. Consequently, the IACUC needs to scrupulously follow the Guide's admonition and receive a valid justification for the use of toe clipping in each case before approval is granted.
Toe-clipping may be considered for research that requires highly individualized animal identification that is permanent and unambiguous, such as for the long term unique identification of potential breeding mice. A written justification for IACUC approval must be submitted prior to using the toe-clipping method. This justification must clearly indicate why alternative methods of identification are not appropriate; it cannot be based solely on the number of animals requiring unique identification, or on the cost of using other methods. If toe-clipping and taking a tail section for genotyping need to be performed on the same animal, the two procedures should be done at the same time if at all possible. Front toes should never be clipped if animals may subsequently be used in grip testing.
Toe-clipping can only be performed on animals ten (10) days of age or younger. Any numbering system used should be designed to minimize the total number of toes clipped per animal. Similarly, a given foot should have as few toes clipped as possible; two is the maximal number. Sharp scissors are recommended for toe-clipping in neonatal rodents. Instruments should be clean and disinfected initially, and blade surfaces should be cleared of debris and wiped with chlorhexidine or 70% alcohol between animals. The aim is to remove only the complete distal phalanx, if possible.