News Notes

New Research Allows Geneticists to Trace Paternal Lines of Horses

By Courtney Price

Researchers recently found information about the Y chromosome in horses, which could identify optimal lineages for breeding and preserving breed diversity.

The Y chromosome has meaningful variation and is important for species diversity, according to Gus Cothran, PhD, a professor emeritus at Texas A&M College of Veterinary Medicine and Biomedical Sciences.

“We can trace the male lineage of horses using the Y chromosome, which was something we could not do before,” Dr. Cothran said. “The Y chromosome has many sections that repeat, and even some that are palindromes—the same forward and backward. It makes it challenging to understand which genes are encoded there,” Dr. Cothran explained.

As technology has improved, computers have made it easier to process these sections of DNA. This enabled them to screen a worldwide collection of horse DNA samples to trace back the roots of modern stallions, according to Dr. Cothran.

“This study allowed us to see major breeding influences and how historical expansion routes contributed to the spread of horses” he said.

Currently, pedigrees are used to find out the horse’s ancestry, which gives information on the traits a horse may have inherited. However, pedigrees are recorded manually, and they may go back only a few generations.

“Our recent research enables us to go back much farther, to see what evolutionary lineages a horse has in its DNA,” Dr. Cothran said. “We can now see the bigger picture of an individual horse’s paternal ancestry.”
Studying the evolutionary history in a horse’s ancestry may soon become a vital part of equine breeding to protect the health and well-being of rare breeds.

“One of the main dangers within breeding programs for some horses is inbreeding, which happens when mating animals are too closely related; in horses, it can cause genetic defects like club foot and loss of fertility,” Dr. Cothran explained. “Thus, both breeders and equine conservationists are interested in using scientific research to promote genetic diversity.

“If you have a horse from a rare breed and there is more than 1 male lineage to choose from, you could, perhaps, select for the rarer of those lineages in breeding, which would help maintain diversity within that breed. With the new analysis capabilities…we may discover that there are reasons to avoid crossing certain male lineages to protect the health of offspring or the future of the breed,” he said. MeV

This article was originally published on the VBSM site. It was edited for space and style. https://vetmed.tamu.edu/news/press-releases/secrets-of-horse-genetics/

For more information:
Radovic L, Remer V, Rigler D, et al. The global spread of Oriental Horses in the past 1,500 years through the lens of the Y chromosome. Proc Natl Acad Sci. 2024;121(49). Epub 2024 Nov. 14. https://www.pnas.org/doi/10.1073/pnas.2414408121