Mapping the horse genome used to be a pie-in-the-sky type of wish for veterinary geneticists: Understanding the genetic makeup of the horse could help them unlock a plethora of equine health mysteries and improve horse care. It was a tough concept to explain to the layperson, journalist, research donor, or horse owner. But the message got through and the completed equine genome sequence is now a reality, clearing the way for advancements in equine veterinary medicine, from new tests for genetic disease to ways of predicting orthopedic injury.

Douglas F. Antczak, VMD, PhD, director of the James A. Baker Institute for Animal Health at Cornell University, gave the John Hickman Memorial Lecture at the 46th Congress of the British Equine Veterinary Association (BEVA), held in Edinburgh, Scotland, Sept. 12-15, 2007. His talk, "The Genetics Revolution," kicked off three days of presentations from some of the best and brightest names in equine veterinary medicine.

Antczak chronicled the beginnings of the Horse Genome Project group, who had seven or eight genes of the horse fully mapped at the group's outset in 1995. This contrasts with the estimated 20,000 genes that are mapped to chromosomes of the horse today. "This has been an unprecedented collaboration that has extended over the past 10 years from 22 laboratories in 12 countries," he explained. "This collaboration has brought us to where we are today," which is to a point where a complete (6.8x) whole genome sequence of the horse is available to researchers worldwide in public DNA databases.

"Horses are large, expensive--they kick, bite, they really are the geneticist's nightmare," he said. "Nevertheless, they've moved to the forefront of modern molecular genetics." The research moved along steadily in the hands of the Genome Project group until 2006, when they were helped by a commitment from the U.S. National Human Genome Research Institute of the National Institutes of Health, who added the horse to its list of mammalian species to be sequenced. The map was rocketed toward completion, and scientists are now at liberty to complete associated equine genetic research much more efficiently than before. While it used to take about six months to sequence an equine gene, now information on a particular gene can be pulled and useful to a researcher in 15 minutes.

Applications that have come out of the genome project during the past 20 years or so have been commercial tests for severe combined immunodeficiency (SCID) in Arabians, hyperkalemic periodic paralysis (HYPP) in Quarter Horses, and lethal white syndrome in frame overo Paint horses. More recent advancements include mapping genes that cause glycogen storage disease in some breeds and hereditary equine regional dermal asthenia (HERDA) in Quarter Horses.

The impact of having the entire sequence available could be staggering. "In 10 years there will be available tests for more genetic defects, and there are more being published every three months," said Antczak.

He believes in light of these recent advancements, genetic ethical issues veterinarians face include:

  • Addressing wastage in the industry (If certain genetic markers are known to be associated with particular conformational defects, will these horses be overlooked in the sales without valid reason? Who says what conformational defects are actually harmful?)
  • Pinching twins in pregnant mares: "Are we contributing to the success of our own profession, or are we making her (the mare) reproduce when she shouldn't?" he asked.
  • The quandary of complex genetic traits: A genetic marker might be responsible for one feature of the horse, but there could be--and probably are--a variety of genetic and environmental components to that marker. Recurrent airway obstruction ("heaves") and skin tumors (sarcoids) are examples, as are conformation and performance, which are strongly influenced by environment.

The completed genome "will change the way in which we think about modifying our feed, training, and care techniques," he said, addressing his veterinary peers in attendance. "I see a very murky but exciting future for us, and I look forward to working with you on it."

Prominent equine researchers in the audience said the industry understands and can handle the ethical issues, but expressed with frustration that money will often prevail: the get of a stallion who throws stakes winners will still sell for high prices, regardless of whether buyers have been told that his foals are likely to develop osteochondritis dissecans or other problems.

A Dutch veterinarian said, "It's a matter of informing the public (of the risks involved with particular genetic problems in a horse's family), and after that, it's up to the breeder."

Another audience member summarized, "If the information (on an animal's genetic predispositions) is there, the purchasers will begin to demand it. This is ultimately purchase-driven, and it will be a very long time before that (purchaser demand for genetic marker information) arrives."

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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