The University of Iowa

Genotyping - Rodent Tail Snipping for Genotyping (Policy)

Policy: The IACUC has provided a set of guidance documents (Policies, Guidelines, and Informational Sheets) for use when planning animal procedures at the University of Iowa. An exception to a Policy must be described and justified in the Animal Protocol and approved by the full IACUC at a convened monthly meeting.

Purpose: The intent of this policy is to describe procedures required for tail tissue collection in rodents for genetic analysis. This policy is intended for use by research staff and Office of Animal Resources staff approved to perform this procedure on an Animal Protocol. This policy is approved by the University of Iowa Institutional Animal Care and Use Committee (IACUC).


    • Mice and Rats 10-24 days old: 
      • anesthesia or analgesia recommended but not required
      • Note: Better quality DNA and higher DNA yield has been reported from tail snips at 18 days of age or younger, due to a lower percentage of ossified sample.
    • Tail snipping procedure:
      • Gently, but securely, restrain animal (manual or mechanical)
      • Snip tail with sanitized sharp scissors or disposable blade
        • Minimize the amount of tissue removed - 2 mm of distal tail has been identified as sufficient tissue to perform multiple PCR reactions 2
        • DO NOT remove more than 5mm of tail
      • Place tail tip into a tissue collection tube
      • Ensure hemostatis (stop bleeding):
        • Apply pressure to the cut portion of the tail with gauze until bleeding has stopped
        • If continuous pressure does not stop the bleeding, utilize a chemical cautery agent (e.g. silver nitrate or Kwik Stop®)
        • Heat cautery can also be used
      • Return animal to its cage and monitor for bleeding for at least 5 minutes
      • Clean off biologic material (e.g. blood or fur) from scissors and sanitize after each snipping


    Note:  Any procedure(s), other than a one-time collection in animals between 10-24 days of age, must be described and justified in the Animal Protocol.  The following are examples of acceptable deviations if appropriate justification is provided in the Animal Protocol:

    • Sampling of neonatal mice under 10 days of age (consult with OAR veterinarian)
    • Sampling of animals greater than 24 days of age
      • Use of a systemic analgesic given prior to tail snipping is required
      • Tailing at this age is potentially painful and should be avoided if possible
    • More than one sample over the life of the animal
      • Limit of two collections, no more than a total of 2-5mm of the distal tail removed over all collections
      • Use of a systemic analgesic given prior to repeat tail snipping is required



    1. Bonaparte, Dolores, Paolo Cinelli, Eleni Douni, Yanne Herault, Alex Maas, Pirjo Pakarinen, Matti Poutanen, Mirentxu S. Lafuente, and Ferdinando Scavizzi.  “FELASA Guidelines for the Refinement of Methods for Genotyping Genetically- modified Rodents: A Report of the Federation of European Laboratory Animal  Science Associations Working Group." FELASA Guidelines for the Refinement of  Methods for Genotyping Genetically-modified Rodents: A Report of the  Federation of European Laboratory Animal Science Associations Working Group 47.3(2013): 134-45.
    1. Hankenson, F CLaire, Laura M. Garzel, David D. Fischer, Bonnie Nolan, and Kurt D.  Hankenson. "Evaluation of Tail Biopsy Collection in Laboratory Mice (Mus  Musculus): Vertebral Ossification, DNA Quantity, and Acute Behavioral  Responses." Journal of the America Association for Laboratory Animal Science 47.6(2008): 10-18.
    1. Jones, Carissa P., Scott Carver, and Lon V. Kendall. "Evaluation of Common Anesthetic and Analgesic Techniques for Tail Biopsy in Mice." Journal of the  America Association for Laboratory Animal Science 51.6 (2012): 808-14.


    Last Reviewed by the IACUC 12/8/2021