Y Chromosome Research and the Fell Pony

Recent results of a study on horse DNA brought to mind parts of Fell Pony history.  The study suggests that modern horse breeding practices have reduced the genetic diversity in male equines.  When I think back to the premium and enclosure schemes of recent Fell Pony history, it’s easy for me to see how this could be true.

The study, summarized in the article “Ancient wild horses help unlock past,” focused on Y chromosomes and was conducted on both modern and ancient horse DNA.  Previous studies on domesticated horses had found that there is less genetic diversity in male horses than in females.  The prominent explanation of this fact has been that the harem mating system of horses “skewed reproductive success of males.”  If this were the case, one would expect to see the same lack of diversity in males in ancient wild horses as in modern domestic ones.  This new study found that was not the case.

Dr. Michi Hofreiter of the University of York led the team of researchers.  He said, “Our results reject this hypothesis as the Y chromosome diversity in ancient wild horses is high. Instead our results suggest that the lack of genetic diversity in modern horses is a direct consequence of the domestication process itself.”  (1)  The study found that even 2,800 years ago domesticated male horses had significantly more genetic diversity than they do now.  (Domestication of horses is assumed to have occurred 5,500 years ago, but a recent archaeological dig in Saudi Arabia has suggested that domestication may have occurred 9,000 years ago. (2))  This result suggests that it is relatively modern breeding practices of domestic horses that have caused the lack of male genetic diversity.

One hundred years ago, the Fell Pony Committee had a premium scheme to encourage the breeding of Fell Ponies.  Owners of Fell Ponies were paid both a flat fee to stand their stallions as well as a per-foal award.  In 1912, the scheme resulted in 217 mares being served by just six stallions, an average of 36 mares per stallion.(3)  In 1947, 31 mares were served by a single stallion in the enclosure scheme at Berrier.(4)  These schemes were considered necessary to preserve the breed and increase the numbers of registered Fell Ponies, so they were used for several years each, often with the same stallions.  It is easy to see, then, how the male/female ratios that resulted could concentrate male genetics rapidly, consistent with what the recent research has found.

In the Fell Pony breed we are dealing with Foal Immunodeficiency Syndrome (FIS).  It has been estimated that as many as 47% of our ponies carry the FIS mutation. (5)  I couldn’t help but think of FIS when I read about this research on Y chromosomes and the lack of genetic diversity in modern stallions.  One knowledgeable Fell Pony breeder has told me that FIS traces to a single stallion, though the breeder didn’t tell me which one.  Given the past practices of premium and enclosure schemes that encouraged breeding lots of mares to a single stallion for several years in a row, we have definitely concentrated the genetics on the male side of our breed.  It’s easy to conclude that FIS is a consequence of this practice.  A friend of mine has suggested that our breed should institute a grading up program to diversify our genetics. (6)  That idea has even more merit now that I understand how little genetic diversity is common in males of equine breeds.

© Jenifer Morrissey, 2011

(1)   http://www.pasthorizonspr.com/index.php/archives/08/2011/ancient-wild-horses-help-unlock-past
(2
)   http://www.pasthorizonspr.com/index.php/archives/08/2011/domestication-of-horses-may-stretch-back-9000-years
(3)   Fell Pony Stud Book Registrations 1898-1980, The Fell Pony Society (FPS), Penrith, Cumbria, p. 21.
(4)   FPS, p. 149
(5)   http://www.horsetrust.org.uk/News-1/Horse-Trust—Funded-Test-For-Fell-Pony-Foal-Syndrome-A–Massive-Success—With-Breeders/
(6)   For more information on grading up and the past use of this technique in Fell Ponies, see Morrissey, Jenifer, “Inspection Schemes and Grading Up in the Fell Pony Breed,” Feather Notes, Willowtrail Farm, Volume 4, Issue 3, July 2011.

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About workponies

Breeder of Fell Ponies, teamster of work ponies, and author of Feather Notes, Fell Pony News, and A Humbling Experience: My First Few Years with Fell Ponies. Distributor of Dynamite Specialty Products for the health of our planet and the beings I share it with.
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