Tissue Collection
Collecting Tissue for Genotyping and Identifying Purpose Bred Mice and Rats
Purpose
The purpose of this document is to provide guidelines to researchers regarding acceptable methods of tissue collection for the purpose of rodent genotyping and identification.
Background
The Institutional Animal Care and Use Committee (IACUC) must approve all methods for tissue collection prior to performing the tissue collection on animals. Tail clipping, ear punching, and toe clipping are acceptable methods of tissue collection for the purpose of genotyping mice and rats. If used, the specific method should be described and approved in the Animal Care and Use Protocol. Reference to this document is sufficient description, provided the guidelines are adhered to as described below.
Guidelines
IACUC recommendations for sampling are as follows:
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Tail Clipping
This method involves amputating a minute portion of the distal tail. At 3-4 weeks, the degree of ossification of the coccygeal vertebrae in the distal 0.5 cm is much less than that at 1 cm. After 4 weeks of age, the degree of ossification is similar at the distal 0.5 cm and 1 cm tail segments. Perception of pain is assumed to be more likely in bony versus cartilaginous tissue. Tail clipping on mice or rats younger than 4 weeks of age does not require anesthesia. Animals should be appropriately restrained during the procedure to minimize trauma. Sterile sharp scissors (must be disinfected between uses) or a sterile scalpel blade per animal can be used for the procedure. Only the distal 0.5 cm (up to maximum 1 cm) should be amputated. Hemostasis can be achieved by using a silver nitrate stick, Quick Stop powder or by applying a gauze square over the site with gentle pressure until bleeding stops. Animals older than 4 weeks of age or animals requiring a second tail sample must be appropriately anesthetized and analgesics given during and following the procedure. A maximum of 1 cm can be amputated.
- Ear Punch
This method involves punching a hole or making a notch in the ear pinna. Commercial ear punches are available and inexpensive. Ear notching using an ear punch is a permanent form of identification (universal numbering system). Ear notch remnants can usually provide enough tissue for DNA sampling during the initial PCR screening. Ear punch samples collected on animals do not require the use of anesthesia or analgesics, however, for identification purposes the animal must be appropriately restrained to ensure proper technique. The ear punch must be disinfected between animals. These devices can be autoclaved.
- Toe Clipping
This method involves removal of the distal phalangeal (coffin) bone of one or more limbs. Toe clipping, as a method of identification of small rodents, should be used only when no other individual identification method is feasible and should be performed only on altricial neonates (mice = 12 days and rats = 7 days). Toe clipping has the potential to induce pain and distress, alter the animal’s gait and ability to feed.
Rats older than seven days and mice older than 12 days of age must be anesthetized for this procedure to ensure proper technique and to minimize pain and distress. Only one toe per foot may be removed. A pair of sterile sharp scissors can be used for this procedure (must be disinfected in between uses). Hemostasis can be achieved by using a silver nitrate stick, Quick Stop powder, or by placing a gauze square over the site and applying gentle pressure until bleeding has stopped.
Procedure: IACUC-32
Date: Feb 23, 2006
Enabled By: UCD IACUC
Supersedes: Sept 2, 2004