IACUC Guideline:

Mouse Tail Clipping ¹

 Rationale:

The mouse-tail clipping procedure is used to obtain tissue to use as a source of genomic DNA for genetic monitoring in mice.

Medical Information:

The tail of a mouse contains a variety of tissues, including bone, cartilage, blood vessels and nervous tissues. In a young mouse (<21 days) the tissue near the tip of the tail is soft and the bones have not completely mineralized. Therefore, removing of the tail tip of a young mouse probably amounts to momentary pain for the animal. As the animal ages, tissue maturation includes mineralization of the bone and increased vascularity. Tail tip sampling performed on an older animal (>21 days) is likely to involve more than momentary pain and distress as well as the potential for significant hemorrhage. ²

Guidelines:

The Institutional Animal Care and Use Committee (IACUC) believes that tail tip removal should be performed at as young an age as is feasible. In most, if not all, cases the procedure can be performed prior to weaning and there is nothing to be gained by genotyping at an older age. Therefore, the IACUC has adopted the following guidelines for tail tip removal. ³

1. Clipping of tail tissue can be performed without general anesthesia in mice less than 3 weeks (<21 days) of age. General anesthesia is required when tail clipping any mouse after 3 weeks of age.
2. The total amount of tail tissue clipped and removed should be the minimum necessary (1-2 mm ideally), but not more than 5 mm. If taking more than 5 mm, it is not acceptable at any age without the use of anesthesia. ⁴
3. Repeated tail clips on a single mouse are discouraged *. If additional tail clips are required, the rationale must be justified to IACUC and the use of anesthesia is mandatory regardless of age or amount of sample taken.
4. Regardless of age or amount of sample, bleeding must be controlled and the mouse observed until it recovers from the anesthesia and the procedure. If less than 2 mm is taken then hemostasis can usually be achieved by direct pressure on the end of the tail. If greater than 2 mm is taken or if direct pressure does not work, the use of chemical cauterizing agents are required and should always be on hand as a precautionary measure. Styptic powder and silver nitrate are two very effective cauterizing agents commonly used for these procedures.

	< 5 mm Samples	> 5 mm or Additional Samples
< 21 days	NO Anesthetic Required	Anesthetic Required
> 21 days	Anesthetic Required	Anesthetic Required
ANY AGE	Bleeding Controlled	Bleeding Controlled

Alternatives:

* Ear punch, an alternative to tail snips: Some investigators have found that they can obtain sufficient material for genotyping mice from samples collected by ear punch or saliva swab.

* Repeated tail clipping: If you anticipate the possibility of needing an additional sample from a mouse at a later date, cut the original sample in half and preserve the extra piece at -20° or -80°C. ⁵

 

Accepted by the IACUC: 11-15-05

Source:

¹University of Pennsylvania, IACUC Guide # 23; http://www.upenn.edu/regulatoryaffairs/IACUCguides.html

²Kansas State University, IACUC Guide #5; http://www.ksu.edu/research/animal/iacuc/iacuc05.htm

³IACUC at the University of Washington; http://www.hscer.washington.edu/iacuc/policies/tailing.html

⁴Penn State IACUC Guidelines; http://www.research.psu.edu/orp/ani/GUIDE/II.htm

⁵University of IOWA, IACUC guides; http://research.uiowa.edu/animal/?get=tbiopsy