Published November, 2010

Genetics is one of the many research focus areas at the University of Kentucky's Gluck Equine Research Center. A subset of this emphasis area is the Animal Genetic Testing and Research Laboratory (AGTRL), which allows horse owners to investigate their horses' DNA and offers a range of tests to the public, including those for genetic disorders and coat color patterns.

The AGTRL is one of only two such laboratories connected with public universities in the United States; the other is at the University of California, Davis.

The AGTRL was founded in 1986, before DNA tests were widely used. At that time the Department of Veterinary Science had begun regularly conducting blood type testing to verify parentage for Standardbred registrations across the country when scientists became aware of a condition called neonatal isoerythrolysis, or foal jaundice, present in about 2% of Standardbreds. The condition occurs in healthy foals and is caused by an incompatibility of blood types between a mare and her foal, which causes a destruction of the foal's red blood cells. The AGTRL research team studied the condition and discovered a way to test a mare and stallion to see if a cross would result in neonatal isoerythrolysis.

"It was a bigger problem in Standardbreds because of the variability in their bloodstream ... Thoroughbreds had a lower incidence because they were much less variable," said AGTRL director Kathryn Graves, PhD.

Graves said the test can also be conducted after the birth of a neonatal isoerthrolysis foal and allows farms to place affected foals with nurse mares.

After the discovery of neonatal isoerythrolysis, Graves said technology started changing. In the mid-1990s DNA became easier for owners to sample and for the lab to test, and genetic markers were established as comparisons to verify parentage or identification.

It was easier to pull hairs from a horse's mane or tail than to have an area veterinarian draw blood when a horse needed to be registered, Graves said. Now there is also no need for temperature regulation of the samples, and shipping time is less of a concern.

With the ease of sampling came the development of more tests for genetic diseases such as junctional epidermolysis bullosa (also known as JEB, commonly found in Saddlebreds) and overo lethal white syndrome (OLWS, a concern in Paint horses). The test for JEB was developed at the AGTRL.

Also available at the AGTRL are tests for the presence of genes linked to coat color. Scientists can test for the e locus gene, which controls presence of red or black hair; the agouti gene, which determines whether a horse is bay or black; the cream dilution gene, responsible for palominos and buckskins; champagne dilution; silver; gray; sabino; and tobiano. The champagne dilution test was developed at the Gluck Center by Ernie Bailey, PhD, professor in the Department of Veterinary Science.

While these tests do not tell breeders exactly what color a foal will be, they do allow scientists to present the possibilities and their probabilities, based on the genetics of both parents.

Graves said most tests are submitted by breeders, many of whom are hoping to learn their horse carries two copies of the gene for tobiano coat color, which always results in a spotted offspring.

Others are curious about whether their horse carries two copies of a gene to make him or her palomino or cremello. For many, the value of their breeding stock depends on the horses' genetic makeup, and stallions are advertised based on their ability to produce uniquely colored foals.

However, Graves said testing has decreased due to a decline in horse breeding because of the economic downturn. Despite the drop in samples submitted, Graves has bright hopes for the future of the lab.

"Right now we're in the 'baby phase' of genetic testing. [We have tests for] things that are easy to find the mutations for and simple mutations that have a blatant affect on the horse," she said. "We've had the completion of the horse gene map, which is very exciting because we now know the location of all the genes in the horse and can begin testing for the location, not just for diseases. We can start developing tests for desirable traits like performance traits and conformation."

The AGTRL uses its revenue for genetic research projects and works with breed registries to identify genetic issues within specific breeds.

To request a series of tests, owners, breeders, and veterinarians can visit the AGTRLwebsite.

Natalie Voss is a UK equine communications intern and recent graduate in equine science and management.