I: Background

 Federal Regulations, including the Animal Welfare Act and PHS Policy for the Care and Use of Laboratory Animals, require appropriate identification of animals used in research, teaching, or training. In addition, genetic samples are often needed for DNA analysis. The Institutional Animal Care and Use Committee (IACUC) must approve all tissue collection and identification methods before performing procedures on animals. This policy outlines standard methods used for identification and genotyping.

II: Related Policies and Guidance

•                  Policy 529-227: Agents for Anesthesia, Analgesia, and Euthanasia

•                  Policy 529-280: Vivarium, Room, and Cage/Tank Cards Postings

•                  Guidance 529-349: Guidelines for Rodent Anesthesia and Analgesia

III: Policy

A: General Identification

 

1.  Cage Cards - At a minimum, the following information is required for animal identification at the cage card level:

 

a) Animal Use Protocol number

b) PI name

c) Contact person (if different from PI)

d) Species

e) Source (e.g., vendor, colony)

 

 

B: Procedures

 

1.  Tail Tip collection in mice:

 

a) General anesthesia is required for mice older than weaning age (>21 days of age) recommended for mice over 17 days of age.

 

b) Investigators should consider giving an analgesic (e.g., buprenorphine 0.05 mg/kg SQ, carprofen 5 mg/kg SQ, or meloxicam 5 mg/kg SQ) to adult mice following general anesthesia.

 

c) Sharp, sterile scissors or razor-blades are used to remove the tip of the tail. Scissors/blades should be sterilized in between cages of animals. Tools should be sterilized between animal cages by wiping off organic material with alcohol followed by applying heat (hot bead sterilizer). Scissors/blades and work surfaces should be cleaned of all organic material between animals to prevent DNA contamination.

 

d) No more than 5mm of tail tissue may be removed per rodent per tissue collecting procedure. Repeat tail biopsies require anesthesia and must be justified in the AUP.

 

e) Bleeding should be minimal. If bleeding occurs, it should be stopped by applying gentle pressure or a hemostatic agent over the site.

 

2. Ear Notching or Punching in Rodents

 

a) Anesthesia is not required for mice at any age but is required for rats over three weeks of age.

 

b) The ear punch should be cleaned of all organic material between animals to prevent DNA contamination. In addition, the ear punch should be sterilized between animal cages by wiping off organic material with alcohol followed by applying heat (hot bead sterilizer).

 

3. Toe Clipping in mice

 

a) The practice of toe clipping solely as a means of identification is unacceptable. If genotyping will be performed in conjunction with identification via toe clipping, the investigator will be required to assess the use of alternative systems and provide a written justification for review and approval by the IACUC.

 

b) Only altricial neonatal mice up to 7 days of age should undergo this procedure, which can be done without anesthesia. Anesthesia is required if toe-clipping is performed at > 7 days of age, and the rationale for performing the procedure at > 7 days of age should be included in the scientific justification. The OCV should be contacted to confirm the appropriate technique and to verify proficiency.

 

  c) Instruments (such as scissors or scalpels) should be cleaned of all organic material between animals to prevent DNA contamination. In addition, the instrument should be sterilized between animal cages by wiping off organic material with alcohol followed by applying heat (hot bead sterilizer). After removing the digit, hemostasis must be ensured by applying gentle pressure with a gauze sponge or using a silver nitrate stick or styptic powder. 

 

4. Other Identification Methods:

 

a) Microchips: Injecting a small microchip transponder subcutaneously between the scapulae is permissible. The use of a reader detects the microchip. The size of the microchip determines if anesthesia is needed. Contact OCV for assistance.

 

b) Micro-tattooing: A permanent mark made using a needle and ink can be applied to the tail, toes, or foot pads.

 

c) Ear tagging: A metal tag with a unique identification number may be attached to one ear.

 

d) Non-toxic dye/markers: Sharpies can be used to mark the tail or fur. However, the mark must be reapplied every 24 hours to ensure the mark is still visible. Animal Marker is another product available that can be used on fur. Animal Markers can last between 6-12 weeks. Non-toxic hair dye may also be used.

 

 

5. Caudal Fin Clip in Fish

 

a. Before this procedure, fish must be anesthetized via immersion in an anesthetic (e.g., MS-222).

 

b. The fin is clipped with the sterile blade or scissors at a point not greater than halfway between the tip of the fin and the body. Scissors/blades should be sterilized in between animals using heat (e.g., hot bead sterilizer, flame) or chemical methods (e.g., 2% glutaraldehyde 12-minute contact time, or a 1:10 dilution of bleach) and rinsed free of chemicals before use in animals.

 

c. The caudal fin will regenerate within two weeks if the procedure was performed correctly.

 

 

6. Other species:

 

a. All cats must be identified by a tag, tattoo, or collar, which the research facility or vendor applies to the live cat

 

b. Rabbits usually arrive from approved vendors with an ear tag or tattoo used for identification purposes. All cages should include a cage card; see I.1 for minimum requirements.

 

c. Field researchers should consult with the latest publications when working with specific species on the field to confirm the identification procedure and method are the least invasive and do not hinder the animal if captured and released. All identification procedures performed on the field must be reviewed and approved by the IACUC.

 

 Approved on 9/15/2022; Revised: 05/12/2025