Tail Snips, Tattoos and
Identification Procedures Training Presentation
University of South Florida
(July 2005)
Course Objectives

This presentation will outline common methods used
to obtain tissues for DNA/RNA sampling, as well as
prevalent identification methods.

Tissues commonly used for assessment of DNA
and RNA in mice are the tail and ear.

Simple identification methods include ear
punching, ear notching, placement of ear tags, and
tattooing of the tail or foot pad.

(NOTE: Any tissue collection over the age of 21
days and/or over 5cm requires anesthesia; use
of local anesthetic agents is suggested for
animals under 21 days of age).
Ear Punches/Notches

In order to establish which
is the right or left of the
animal - position it so that
the belly is down and the
head is facing away from
the you.

Restrain, as appropriate, to
facilitate performing the
punch or notch.
Ear Punches/Notches



A single hole or notch
may be made using an ear
punch tool.
Notches are
accomplished by
positioning the
instrument at the edge of
the ear, resulting in a hole
that is only partially
surrounded by tissue.
Notches may also be
made by removing a small
wedge shaped piece(s) of
tissue with small scissors
Ear Punches
Ear Notches



Tissues removed during this
process are generally ample
enough to allow for genetic
testing, especially when PCR
is utilized.
Sterile instruments and tubes
are used to obtain and
manipulate the tissue after
collection, and should be
sterilized between animals.
Multiple punches may be
made to collect enough
tissue for analysis – each
punch is approximately
0.5mm in diameter.
Ear Punch/Notch Code




Right ear notch or hole indicates a single
digit.
Left ear notch or hole indicates a multiple
of ten.
One hole located in the middle/center of
the Left ear = 100
One hole located in the middle/center of
the Right ear = 200
Ear Punch/Notch Code

Holes/notches begin
at the top of the
animal’s ear and
progress along the
outside edge of the
ear to the bottom
portion of the ear.

There are three basic
positions on the outer
portion of each ear
and the numbers
progress as
illustrated.
Tail Snipping

Anesthesia is required for mice
over 21 days of age!

Sample should be < 0.5cm
 DNA does not proportionally
increase if tail fragments larger
than .05cm are used.

Scissors or scalpel are both acceptable - both
must be sterilized between mice.
 Scalpel use is preferred by Comparative
Medicine Staff.
Tail Snipping

Sterilization between
animals:
 Use of the bead
sterilizer provides a
two for one punch:
 Hemostatsis and
cautery.
 Complete
sterilization
between animals.
Tail Snipping
Sterilization between
animals is important !
• You don't want to cross contaminate DNA
samples !
• Wiping with alcohol will not prevent this
from occurring (contact time is too short
and may not remove or destroy all
DNA/RNA).
Tail Snipping

Tattooing should be
completed first, if
applicable.

Insert the scalpel blade
into the beads ~15sec.
 Just the blade itself don't introduce past
the tip, or it will heat
the handle (could
burn yourself)
Tail Snipping

To perform the snip:
 Press the blade
through the tissue.
 Hold the flat
surface of the
blade against the
tip - the residual
heat will cauterize
to the area.
Tail Snipping
Use of a hard surface
is recommended to
facilitate asepsis &
cleaning. It also
provides a suitable
surface to push the
blade into with no
damage to
underlying surfaces.
(Note the use of hard
Plexiglas or a glass
Petri dish - can be
used with or without
disposable pad)
Tail Snipping

Many labs use VetBond /glue for hemostasis

Can cause an exothermic reaction that often
makes the mouse rip off the scab once
placed back within the home cage.

Use of silver nitrate sticks is another
popular choice (Note: don't 'roll' the tip
around, but just sort of 'plug' the stick into
the end of the tail).
Ear Tagging
The animal is positioned, as with the ear punch
method, belly down, facing away from the
handler.
The ear tag is pre-loaded into a
crimping device. The mouse is restrained.
The tag is applied to the left ear so
that the self piercing portion is firmly
attached through the interior
portion of the ear tissue.
The tag should be applied so the number is visible to
the outside of the ear.
Ear Tagging
Many animals will scratch or pull out tags.
Care must be taken to position the tag so
that it does not extend too far past the ear
edge, but not so close as to wrinkle the ear.
Tail Tattooing
The animal should be properly restrained or
anesthetized, in accordance with existing SOPs and
IACUC guidelines, before attempting to tattoo.
The most common instrument used on rodents is
the tattoo pen. Tattooing is the preferred method of
identification for animals being utilized on long-term
projects, while tagging is commonly used on
animals involved in short term models.
The numbers used will be determined by the user.
Tail Tattooing
The tattoo pen is normally
used on the tail, but can also
be used on the foot pads for
long term identification.
Several practice attempts
should be completed to
learn proper technique with
the tattoo pen, since
legibility is a major factor.
Tail Tattooing
The area to be tattooed is
gently cleansed prior to
tattooing.
The area can be sprayed with a numbing agent to
alleviate potential distress – these sprays provide
transient effects only, and the tattoo should
proceed quickly following prepping of the area.
A thin layer of tattooing oil will be applied in an
even manner across the entire area.
The area prepped should extend just beyond the
tattoo pattern. The pen is positioned so that the
needles just pierce the tissue.
Tail Tattooing
The numbers will be
arranged so that they
progress down the tail
beginning at the base and
extending to the tip.
Care must be taken to not tattoo
directly over any visible
underlying vasculature.
Once the tattoo is completed,
any excess ink is wiped away.
Tail Tattooing
•
All tattoo equipment (especially
needles) should be cleaned
thoroughly at the end of the session.
OR as directed by the PI:
• between animals
• between cages
• between strains
• between rooms and protocol
assignments
AUTOCLAVE needles weekly at a minimum!
Special Thanks



Monica Torres – SRB Quarantine
Manager
Jim Gildea – SRB Facility Manager
Amanda Rockhill and Omar Guevarra
SRB staff members
And the MICE who so graciously “posed”
for us!