Policy 9 – Mouse Toe Clipping for Identification
Version 2.0
Approval Date: 1/22/07, 3/5/13
Purpose – The purpose of this policy is to provide investigators directions for the proper techniques
associated with toe clipping, an acceptable, permanent form of animal identification.
Background – Toe clipping is a method that involves a numerical scheme in which the first bone of
certain toes is removed with a sharp instrument for identification of small rodents.
“As a method of identification of small rodents, toe clipping should be used only when no other
individual identification method is feasible. It may be the preferred method for neonatal mice up to 7
days of age as it appears to have few adverse effects on behavior and well-being at this age (6,7),
especially if toe clipping and genotyping can be combined. Under all circumstances aseptic practices
should be followed. Use of anesthesia or analgesia should be commensurate with the age of the animals
(8).” – the Guide (1)
Policy –
Toe clipping will be considered under the following conditions:
1. Justification: A written explanation to the IACUC of why it is necessary, including why alternate
methods are unsatisfactory.
2. Animal age: Toe clipping should only be performed when mice are between 1-12 days; the
preferred age is 7 days old. (6)
3. Number of toes: Limited to a maximum of four toes and no more than one per foot. Do not cut
the hallux ("dew-claw" or "little toe" of the forepaw) as this may decrease the rodent's grasping
ability. Also, confirm bleeding has stopped prior to returning animal(s) to cage(s).
Procedure:
1. No anesthetic is required for animals age ≤7 days old; animals between 8-12 days old require use
of general anesthesia.
2. Use sharp scissors or a blade sanitized with 70% ethanol or antiseptic solution (Clidox, povidone
iodine, chlorhexidine, etc.)
3. If bleeding is observed, apply gauze with gentle pressure or Clotisol (anticoagulant powder) to
the affected region for hemostasis.
Any exceptions to this policy must have IACUC approval
1
References 1) The Guide for the Care and Use of Laboratory Animals, 8th ed, NRC Press, 2011, page 75.
2) NIH Guidelines for Toe Clipping of Rodents
http://oacu.od.nih.gov/ARAC/FinalToeClip0504.pdf. Revised 5/12/04
3) Yale University, IACUC Policy, revised 6-2006
http://iacuc.yale.edu/policies/ToeClippingGuidelines.pdf
4) Dartmouth University IACUC policy, 2003
http://dms.dartmouth.edu/arc/iacuc/policies.shtml
5) Johns Hopkins University IACUC policy, 2005
http://www.jhu.edu/animalcare/committee_toe_clipping.html
6) Schaefer DC, Asner IN, Seifert B, Burki K, and Cinelli P. 2010. Analysis of physiological and
behavioral parameters in mice after toe clipping as newborns, Laboratory Animals 44: 7-13.
7) Castelhano-Carlos MJ, Sousa N, Ohl F, Baumans V. 2010. Identification method in newborn
C57Bl/6 mice: a developmental and behavioural evaluation. Lab Animal 4:88-103.
8) Hankenson FC, Garzel LM, Fischer DD, Nolan B, Hankenson KD. 2008. Evaluation of tail biopsy
collection in laboratory mice (Mus musculus): vertebral ossification, DNA quantity, and acute
behavioral responses. JAALAS 47(6): 10-18.
2