Objective—To determine whether microchips used
for identification migrate after implantation in horses,
donkeys, and mules.
Animals—53 horses, donkeys, and mules.
Procedure—Twenty horses that had had microchips
implanted in the nuchal ligament at a veterinary teaching
hospital from 1996 through early 2000 were
included (group 1), and the poll-to-withers distance
and location of the microchip were determined, measured,
and recorded. Additionally, the poll-to-withers
distance was measured in 16 horses, 12 donkeys, and
5 mules (group 2), and microchips were implanted in
the nuchal ligament on the left side of the neck. Fortytwo
to 67 days after implantation, the location of the
microchip was determined, measured, and recorded.
Results—Microchips implanted in the nuchal ligament
≤ 4 years previously did not migrate. All
microchips were detected with a multimode identification
tag reader from the left side of the neck in the
midcervical region, and microchips were located at
the midpoint between the poll and withers for all 53
horses, donkeys, and mules.
Conclusions and Clinical Relevance—Microchips
implanted in the nuchal ligament ≤ 4 years earlier did
not migrate in horses. Microchips may be useful for
identification in horses. (J Am Vet Med Assoc 2003;