Natural, manmade, technological ID methodologies give DVMs choices to present to clients; uniform government mandates coming
Jun 01, 2004
Editor's Note: This month Dr. Kane will review natural and manmade horse identification modalities. Next month, he will explain technological modalities, including microchips and the United States Animal Identification Plan.
Regardless of the methodology, each has its proper application. Though some may be fallible in specific circumstances, the proper choice is the one that is most useful, convenient and easily recognizable.Up to now, each horse registry or organization has chosen a method/s that suits its purpose. This review of horse identification methodologies provides basic information for the equine practitioner and his/her clients. With the pending advent of the United States Animal Identification Plan, some of this discussion might be moot, though, regardless of what may be the mandated modality in the future, other methods of horse identification might still be viable as adjunct forms of identification.
Natural I.D. methods
Though many of these features are not as distinctive as chestnuts or DNA-based information, they do represent genetic phenotypical characteristics, and provide the horse owner with quick visual evaluation and simple recognition.
Signalment includes coat color, and markings such as facial blaze and foot stockings, or the elaborate coat-color patterns of a Pinto.
Coat color and markings are not unique enough to be absolute evidence for determining horse identity, and unfortunately can be altered by a skilled unscrupulous horse thief.
More distinctive, as are human fingerprints, are the oval plates of horny epithelium called chestnuts. These callosities growing like the hoof from enlarged papillae of the skin, are found on the inner face of the forearm, above the carpal joint in all species of Equidae, and in the horse, occur near the upper extremity of the inner face of the metatarsus, on the inside of the foreleg above the knee or on the inner surface of the hock.
They are evidently rudimentary structures, which it is suggested may represent glands (Lydekker, Proc. Zool. Soc. London, 1903, vol. i.), or are thought to be remnants of the first toe.
The pattern on the surface of chestnuts is unique to each horse. Impressions can be made of them using fingerprint-like technology. Like coat markings, unfortunately, they, too, are easily altered (surgically), and can be done so by the same skilled dishonest horse thief.
Similarly distinctive as coat markings or chestnuts, are the trichoglyphs or hair whorls, found throughout the coat pattern, especially on the neck.
Both the Morgan and Thoroughbred registries use these "cowlick" patterns within their records. These whorls are naturally formed during embryonic development and remain throughout the horse's lifetime.
Though no outer body tag is visible, DNA testing and blood typing provide a foolproof indicator of absolute recognition. Both methods are commonly used in horses for paternity and registration verification. If an animal has a DNA test on file, this technique may be used for theft or loss detection as well.
"The DNA of equines, depending on what part of the DNA one is looking at, may be very similar to what we see in people, or very dissimilar," says Joy Halverson, DVM, director of QuestGen Forensics. "It can also be very similar between individual horses, or if you look in a different place, it can be very dissimilar. It is the dissimilar parts of the DNA that are used for identification."