DIRECTIONS: Review the following material. Keep copies of guidelines with applicable protocols. You may find it helpful to post a copy of these guidelines in your laboratory. Questions should be forwarded to the APLAC office, 723-4550.
TRAINING: Training in these techniques and the humane treatment of laboratory animals during the procedures is taught by the Veterinary Service Center (VSC) staff. All new personnel who will be performing these techniques should contact VSC staff for training (725-9901).
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GUIDELINES FOR TAIL CLIPPING MICE
These guidelines have been written to assist Protocol Directors in obtaining blood/tissue samples from transgenic mice to determine the presence/absence of a particular gene product. When performed properly, tail clipping is a safe, effective, and humane procedure that causes minimal or transient pain and distress.
I. Humane Considerations
In young mice, the tissue near the tip of the tail is soft and the bones have not completely mineralized. Depending on a mouse’s genetic background, ossification of caudal (tail) vertebrae occurs between 2 and 4 weeks of age. As the animal ages, tissue maturation results in mineralization of bone, increased vascularity, and a greater potential for the animal to experience pain and distress during tail clipping. In order to minimize the potential for pain and distress, it is recommended that tail tip sampling be performed on mice that are 10-17 days of age. Recent research has also shown that higher yields of DNA content can be obtained from the distal tail tissue of younger versus older mice. [1] Tail tip sampling performed after a mouse is weaned (>21 days) is likely to cause more than momentary pain and distress, as well as the potential for significant bleeding. Therefore, animals over 3 weeks of age (>21 days) should first be anesthetized with a short acting anesthetic (e.g., isoflurane) before tail tip sampling.
II. Methods
Tail sampling should be performed using sharp, clean scissors or industrial blades. Instruments that have been autoclaved, chemically disinfected, or exposed to a glass bead sterilizer are preferred for this procedure. Transverse cuts should be made by holding the blade or scissors perpendicular to the tail. If tail biopsies are performed on multiple mice, instruments must be disinfected appropriately (e.g. Virkon™) between animals. Additionally, instruments must be replaced (blades) or sharpened (scissors) regularly to minimize tissue trauma caused by blunted instruments.
The smallest possible section should be removed (2-4 mm is recommended), but no more than 5 mm may be taken at any age without the use of anesthesia. Regardless of the size of the sample, bleeding must be controlled at the biopsy site by applying manual pressure with sterile gauze and through the application of a styptic powder or tissue adhesive. The animal should be monitored until fully recovered from the procedure/anesthesia.
It is understood that sampling may occasionally have to be repeated. Under these guidelines, tail clips can be performed up to three (3) times without a specific justification in the approved protocol for repetitive sampling. If four (4) or more tail clips are required, a rationale must be provided within the relevant protocol, submitted to, and approved by the APLAC prior to performing the procedure. Regardless of the animal’s age, when obtaining more than one tail sample anesthesia is required (refer to table below).
