Britain may be renowned for the rise of the Thoroughbred, but its oldest established horse breed is actually the Cleveland Bay.
It is the only native warmblood horse breed in Britain, with a breed history going back more than 600 years.
Scientists have been using genetic tools to unveil the ancestry and diversity of many horse breeds in recent years, exploring the effects of inbreeding on the animals’ health, especially so in small populations, and examining the potential impact of losing a breed to the species’ overall genetic diversity.
In fresh research carried out at Texas A&M University, scientists have analyzed the genetic variability in Cleveland Bay horses and investigated its genetic relationships with other horse breeds.
The breed has a rich history. It spread from Britain, growing in popularity in the United States. By the 1900s, the number of registered horses there had risen to more than 2000. However, this number decreased to fewer than 200 by 2009, resulting in the American-based Livestock Conservancy listing it as a critically endangered breed.
Likewise, in Britain, the Rare Breeds Survival Trust listed the Cleveland Bay as a breed of critical concern as there were fewer than 300 breeding females registered worldwide.
Today, the breed is used for recreational riding, driving, and equestrian competition.
Most are used for breeding purposes, but many are kept as companion animals.
The majority of purebreds reside in Britain, with North America having about 25% of the total population. A handful of purebreds are in continental Europe, Australasia, Pakistan, and Japan.
For their research, Anas Khanshour and his colleagues looked at the DNA of 90 Cleveland Bay horses sampled in the United States, and compared them to a total of 3447 horses from 59 other breeds from Europe and the New World.
They found that genetic diversity in the breed was less than that for the majority of other tested breeds.
In fact, it was well below the variation levels for almost all other breeds and ranked as the third-lowest after the Friesian and Clydesdale, both of which are known to be highly inbred breeds.
“This low variation is an indication that active conservation measures for the breed should be undertaken,” the study team said.
“Many horse breeds have disappeared completely or been drastically reduced in number within the past one hundred years, and such low variation indicates that the Cleveland Bay could be at risk.”
The evidence suggested no direct relationship between the Cleveland Bay and Thoroughbred but suggested that Turkman horses – likely in the lineage of ancestors of the Thoroughbred – were a possible ancestor.
As expected, the strong input of British draft and pony breeds were identified in the breed’s lineage.
“Our findings reveal the genetic uniqueness of the Cleveland Bay breed and indicate its need to be preserved as a genetic resource,” the researchers wrote in the journal Diversity.
The authors noted that interest in reviving the breed began in the late 19th century when the studbook was first introduced.
“Since that time there has been a continued interest to keep the breed from extinction, although a serious threat to the breed in modern times has been the crossing of the Cleveland Bay with other breeds to produce sport horses.”
They say genetic testing and detailed pedigree analysis provide a mechanism that can suggest the best matings to make in order to maintain the present levels of diversity within the breed.
“Considering the breed’s own mixed history, as well as its influence on other breeds across Europe and America, an in-depth genetic evaluation of the breed (possibly genome sequencing) seems appropriate.
“The Cleveland Bay is unique among world horse breeds and conservation is important.”
The full study team comprised Khanshour, Rytis Juras and Gus Cothran, all from Texas A&M University; and Eleanore Hempsey, from Northland Pioneer College in Winslow, Arizona.
Genetic Characterization of Cleveland Bay Horse Breed
Anas M. Khanshour, Eleanore K. Hempsey, Rytis Juras and E. Gus Cothran.
Diversity 2019, 11, 174; doi:10.3390/d11100174