Blood Typing and Identification; More Than Parentage

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The University of Kentucky's Blood Typing Research Laboratory, headed by Gus Cothran, PhD, has made many advances in using the genetics of horses in parentage verification. However, Cothran said there are other uses for this science. In this article we find out some of those uses.

Blood typing has been used by horse breed registries for many years as a means of identification and parentage verification. Due to the number of gene marker systems tested, blood typing is an extremely powerful means of identification. This power also has been used in a variety of other circumstances that are not so well known.

One of these areas is drug testing.

If a horse tests positive for a prohibited drug after a race, owners or trainers may claim that the blood or urine sample with the positive test was not taken from their horse. Blood typing methods can be used to compare the urine or blood samples that need tested positive for the drug with another sample drawn from the suspect horse.

From the blood sample 10 or more gene marker systems can be tested. From a urine sample only fie marker systems can be typed and this requires intensive concentration of proteins in the urine. A single difference in the types is proof that the samples came from different individuals. However, if the two samples are the same, this is not proof that the samples are from the same individual.

It is possible to give an estimate of the probability of two horses having identical types based upon the frequency of the genetic markers within the breed. For Thoroughbreds, the probability of two individuals having identical types at the five systems detectable from urine is 1 in 15 for the most common markers. If less common markers are found, the probabilities become very small. When all the genetic markers normally tested by blood typing can be use, the probability that two Thoroughbred horses will have the same type is no more than 1 in 25,000. For breeds such as Quarter Horses, the probabilities exceed one in a million.

The Equine Blood Typing Research Laboratory of the University of Kentucky has performed several such comparisons of drug positive samples with blood samples of the horses provided by the owners. In all cases, the types have been the same.

Another case where the laboratory was requested to use the identification poser of blood typing involved a horse that ha a positive Coggins test for equine infectious anemia (EIA). When a horse tests positive for EIA, restrictions imposed by states differ considerably, but the horse is usually quarantined or destroyed. In this instance, an individual was attempting to sell a horse that was suspected of being EIA positive. The state veterinarian provided the sample used for the Coggins test and a blood sample freshly drawn from the horse in question. The blood types of the two samples were identical and the owner of the horse was fined.

The power of blood typing as a tool for identificaiton has many potential uses. However, its primary use remains parentage verification to maintain the integrity of the stud books of horse registries.