IACUC Policy/Guideline: IACUC Guideline on Rodent Tail Biopsy
Procedures
Purpose/Scope/Application: The purpose of this guideline
is to provide guidance on acceptable parameters for rodent
tail biopsy. This applies to all rodent tail biopsy procedures
in Animal Care and Use Protocols.
Revision/Revision History: October
2008, November 2010, October
2011, July 2014, October 2014
July 2014
Date: September 2008
Associated SOP:
References: NIH Guidelines for the Genotyping of Mice and Rats
Procedure:
Amputation of the distal tail is often performed as a means of obtaining tissue for genetic monitoring in
rodents. While this procedure is momentary it involves a variety of tissues, including bone or cartilage, blood
vessels, nervous tissue and skin. There is potential for immediate and longer-term pain from this procedure.
The distal end of the tail is largely devoid of most of these tissues except skin. Therefore, use of techniques
that require 5 mm or less of tail tissue is required for all age animals. All tail amputations require IACUC
approval, however, removal of more than 5 mm or tail snipping in larger (>50 gm) rodents is only allowed in
exceptional cases and requires scientific justification and PRIOR approval of the Institutional Animal Care and
Use Committee. Examples of alternate methodologies include PCR assays that can be performed using blood,
saliva, ear biopsy or very small tail biopsies.
Ideally, mice and rats should be 10-21 days old when this procedure is performed.
For mice and rats 10-21 days of age: Investigators are encouraged to apply local anesthesia to the
tail and to conduct tail biopsy as early as possible within this age range. Local anesthetics (such as EMLA or
topical Lidocaine cream) should be applied to the tail and allowed to take affect for a time period consistent
with the manufacturer’s recommendations. If no recommended wait-time is provided, allow 10 minutes
before performing tail biopsy. Local anesthesia may also be achieved by immersion of the tail in ice cold
ethanol for 10 seconds (this will also serve to disinfect the tail), or by an application of cryoanesthetic spray
(eg. ethyl chloride or Fluori-Methane).
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For mice over 21 days of age, or rats between 21-35 days of age: Investigators are required to use either
local (see above for guidelines on use) or general anesthesia for collection of tissue.
For rats greater than 35 days of age: The use of a general anesthetic is required.
Additional considerations:

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The tail must be disinfected with alcohol prior to snipping. (Do not use iodine solutions as they may
interfere with DNA analysis). Use clean gloves and a sterile sharp scalpel or razor blade. Make one
clean cut through the tail.
Control bleeding with direct pressure. Observe the mouse in the cage after releasing to assure
hemostasis. It may be necessary to cauterize the tail with styptic powder or silver nitrate. The presence
of blood in the cage may increase aggression among cagemates.
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