Varieties of acceptable and recognized methods are available for individually identifying research animals. These include, but are not limited to, ear tags/notches, tattoos, sutured beads, subcutaneous transponders, colored stains, dyes, and freeze brands. The Guide for the Care and Use of Laboratory Animals states "toe-clipping as a method of identification of small rodents, and should be used only when no other individual identification method is feasible and should be performed only on altricial neonates."

Toe clipping is the removal of the last phalangeal (toe) bone of a digit from one or more limbs. It is usually done for the purpose of identification and genotyping of animals. The Food and Drug Administration also discourages the use of toe clipping as a means of animal identification. The UConn Health Institutional Animal Care and Use Committee typically does not approve the use of toe clipping when performed only for the purposes of identification.

The Interagency Research Animal Committee considers toe clipping to be a painful procedure; however, if may be done only after Institutional Animal Care and Use Committee approval provided that the PI can:

• Justify the procedure to the Institutional Animal Care and Use Committee in the submitted animal care and use protocol and identifying what alternative means of identification have first been considered;
• Provide, in writing, in the submitted animal care and use protocol a scientific explanation of why toe clipping is necessary. This should include a discussion of why alternative methods of identification are unsatisfactory; and
• Adequately describe the procedure in the submitted protocol.

Action

• Toes may be removed without anesthesia from up to mice 12 days of age (seven to eight days is recommended).
• Toes may be removed without anesthesia from rats seven days of age or younger.
• Animals over 12 days of age, or animals whose eyes have opened, must be given anesthesia and post-operative analgesics.
• Since the rodents hold food with their forepaws, the Institutional Animal Care and Use Committee will only allow this procedure on hind paws, one tope per paw, and permits the removal of just the first bone.
• The procedure is not recommended for rodents used in psychology research as it may affect the gait or grip strength of the animal.

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References

The Guide for the Care and Use of Laboratory Animals. National Research Council, National Academy Press, 1996. pp. 46-47.

IACUC Guidebook, 2nd Edition, NIH, Office of Laboratory Animal Welfare, 2002. pp. 46.

Good Laboratory Practice Regulations; Minor Amendment, Federal Register, Vol. 54, N. 75, 1989.

National Institutes of Health, ARAC, Guidelines for ToeClipping of Rodents, Revised May 12, 2004.