UK Gluck Publishes Phase One of Genetic Diversity Study

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The first phase of a research study into the genetic diversity in Thoroughbreds is in the books, with researchers from the University of Kentucky's Gluck Center concluding from the phase one portion that diversity among Thoroughbreds “falls within the range for other breeds of horses” despite centuries of human intervention, according to the Gluck Center.

The study, by the Gluck Center's Ernie Bailey, PhD and Ted Kalbfleisch, PhD,, and Jessica Petersen, PhD, from the University of Nebraska-Lincoln, is based on sequencing the entire genome of Thoroughbred horses, and is published in the Equine Science Review of the University of Kentucky.

According to Dr. Bailey, the completion of their first phase of research in 2021 documents that the diversity among Thoroughbred horses is consistent with that found for other domestic animals and that it falls within the range for other breeds of horses.

In a press release Thursday, the team at Gluck called the study “the most comprehensive analysis of the genetics of the U.S. Thoroughbred to date. Previous studies of Thoroughbred diversity were based on sampling small subsets of the genome,” the release says.

“The goals of the study are to create a database that catalogs the variation across the genome of today's Thoroughbred horses and to generate anonymous (by horse) data that will create a foundation of knowledge for use in monitoring changes in genetic diversity over time,” they write.

During the first phase of the study, 1,000 Thoroughbred samples were collected from horses in Kentucky, California, Florida and New York. Pedigrees of the horses were examined and 120 were selected for whole-genome sequencing to capture as much of the genetic variation of the population as possible. As a result of sequencing these horses, the study aims to create a catalog of 15 million DNA variants among U.S. Thoroughbreds which can be used to monitor future changes in the Thoroughbred population as well as to construct computer models to assess how changes in breeding practices may affect the genetic structure of the population.

The second phase of research, now set to get underway, will be a sequencing project that aims to help protect the breed from deleterious recessive genes. The appearance of variants will be identified, and programs will be used to predict whether those variants might have a potentially negative effect on a gene. Additionally, the team is interested in using part of a survey of the whole breed to get at overall frequencies of genes.

“We can whole genome sequence every animal that is suspected of suffering from a deleterious recessive condition and look for possible causes; if none are proven we can archive the DNA in a database for comparison with future horses that appear with similar disease phenotypes,” Bailey said. “If we wait until a recessive deleterious disease occurs in 1% of the population, then 18% of all Thoroughbreds will already be carriers. This approach allows us to detect such genes before they become so prevalent.”

“Importantly,” the press release concludes, “these data will be publicly available so researchers at other institutions can perform studies of specific traits or genes. The genetic data, and the approach used in generating them, also represent a new tool available for breeders to use in maximizing the genetic potential of each foal and in ensuring the Thoroughbred's status as an elite population of equine athletes.”

Those interested in learning more about the project are invited to contact Dr. Bailey at [email protected]. Those interested in supporting this project through financial contributions may contact Danielle Jostes at [email protected].

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