(Photo sidebar: Although the CS Fund study did not discover the genetic basis for the differences between curly-coated horses and their straight-haired relatives, it did establish that the unusual coat may crop up as a recessive trait in the offspring of two straight-haired parents, but more often it is the result of a dominant gene passed directly from parent to child.
Domestic breeds of animals have a way of falling out of favor, replaced in some cases by technology and in others by the fickleness of human fancy. But, as the CS Fund, a grant-making, California-based foundation, sees it, the loss of an unusual breed of sheep or a strain of curly-coated horse represents more than the disappearance of a bit of living history. Regardless of its current popularity in the marketplace, each breed, with its unique combination of inherited characteristics, represents a genetic "library" from which future breeds may originate.
In an effort to prevent the loss of these minor breeds' gene pools, the CS Fun commissioned a pilot study of the American Curly Horse, a breed numbering fewer than 1,000, whose signature kinky coat and obscure origins set it apart from the mainstream of modern horsedom. What the study found may help save the Curly Horse as well as provide the means through which other threatened domestic equine breeds, including the Shire, Cleveland Bay, Hackney, and Lipizan, may survive.
The CS Fund's study combined three approaches—laboratory analyses, pedigree searches, and painstaking examination of written and oral historical records—to define the Curly breed. A research study performed in 1975 by Keith Farrell, PhD, of Washington State University, had already disclosed that the only significant difference between curly horse hair and straight horsehair is in the shape of the shaft. As with human hair, curly horsehair is oval in shape while straight hair is round.
When D. Phillip Sponenberg, DVM, PhD, of the Virginia-Maryland Regional College of Veterinary Medicine in Blacksburg, Virginia, examined the first two stud books of the American Bashkir Curly Registry, he discovered that two mechanisms appear to govern the appearance of curly coats in offspring. Some registered Curly Horses had been produced by two straight-haired parents, and, therefore, the characteristic had resulted from a recessive gene. This genetic "hiccup," if you will, can pop up in nearly any breed of horse, but it probably occurs most often in Percherons. The majority of the registered Curly Horses, however, were products of matings in which at least one of the parents was also curly coated, suggesting the existence of a dominant gene. In other words, the coat characteristic must be visible in the parents to appear in their offspring.
An important genetic distinction exists between the two varieties. "The recessive type," says Shan Thomas, administrative director of the CS Fund, "is first and foremost a member of his parent's breed. He is a Missouri Fox Trotter or Quarter Horse upon whom nature bestowed a curly coat. The second, dominant type might be a breed." Currently, the American Bashkir Registry does not distinguish between the two types.
Blood-typing of 200 curly-coated horses as well as 12 straight-haired horses of Curly Horse pedigree were then performed by An Bowling, PhD, of the serology laboratory at the University of California-Davis. The intent was not to verify parentage, as is usually the purpose of the procedure, which identifies and compares blood components. Instead, the CS Fund was hoping the blood would provide some clues as to how a horse becomes curly coated, whether the Curly Horse is distinct genetically from other breeds of horses, and whether there is any difference between the recessive and dominant types.
Although the blood-typing results verified the findings of the other areas of research, they did not identify characteristics unique to the Curly Horse. "There was no single marker common to all horses with curly coats," says Thomas. "If one had been found, this would have led to further study to see if such a marker were directly related to the gene for curly hair."
Genetic diversity was the primary finding of Bowling's work. Within the group of sampled horses, 110 of a possible 135 equine variants were present. This high number is not surprising, says Bowling, in a registry with an open studbook and active crossbreeding program. About half of the markers identified were "rare and unusual," a rate consistent with other breeds, but they were present in only four percent of the tested population. Blood-typing of one Curly disclosed a variant that had not been identified in any North American horse tested but only among South American horses of Spanish ancestry.
Bowling found that the blood components of the 212 tested horses most closely resembled those of the Quarter Horse and Morgan, breeds commonly used for crossbreeding. But a few of the horses also had some variants not usually found in modern North American breeds.
Photo sidebar: Benny Damele, the last of a Nevada ranching family associated with the breed since the '30s, stands with his gelding Shoshone, who exemplifies the stock-horse type of Curly Horse.
Interestingly, these components are present in the blood of the straight-haired feral horses of Nevada's Great Basin region. Three separate groups of Curlies from Nevada, Canada, and the Dakotas retain the most remnants of the original genetic pool, indicating that these horses are likely descendants of feral stock. The result, says Bowling, is that the horses are a "source of some unusual genetic material that can't be found elsewhere." At the same time, Curlies carry a heavy mix of characteristics common to other domestic breeds.
In the historical section of the study, four theories of the breed's origin were scrutinized. The unusual coat has variously been ascribed to the introduction of horses from Russia or from South America, mutations in native-born stock, and the remnants of pre-Spanish horses that unaccountably escaped extinction when all other equidae on the continent were wiped out eons before. Though the study did confirm the presence of curly-coated horses in both Russia and South America, it was "unable to prove that a dominant curly-coated horse breed was introduced or imported to North America," says Thomas. It also confirmed that the Curly Horse did not obtain its unique coat from the Russian Bashkir breed, which, in fact, is a straight-haired horse. Instead, evidence appears to point to a "spontaneous mutation" or adaptation of feral horses and that this adaptation can be the result of either a dominant or recessive gene.
"From both the empirical evidence and the blood work," says Thomas, "there is justification for two and possibly three coincidental mutations that resulted in curly horse breeds in Russia, North America, and South America. These three breeds have common ancestors. You don't see these mutations among horses with pony ancestors, for example. Isolated mutations are not uncommon in nature. We suspect that in these three separate groups of horses, the mutation was instigated or supported by severe environmental conditions. There is good anecdotal evidence that curly-coated horses can survive cold better than those with straight hair. And interestingly, the regions where these three curly-haired groups developed are all similar in environment, being high-altitude plains."
The fact that a curly coat remains in these horses, continues Thomas, "is only one sign of a breed that once existed and has now been nearly crossbred out of existence. The Curly Horse breed is now three distinct types: the stock-horse type from crosses with Quarter Horses, Appaloosas, and Paints; the Fox Trotter type; and a more-refined type from crosses with Arabians, Morgans, and Saddlebreds." Although the curly coat remains in some of these crosses, the horse is genetically more Quarter Horse or Morgan or Fox Trotter than pure Curly.
Owners and breeders of curly-coated horses can go in several directions now that breed genetics are better understood, says Thomas. "If interested, they could attempt a regeneration program. With attention to genetics and by tapping the three pockets of original gene pool left, they might be able to use linebreeding to recreate what once was. DNA research, though expensive, would help this project significantly by giving very specific information about group membership. Unless this happens, the original Curly Horse breed can be considered extinct.
"If breeders choose, alternately, to move forward from here," she continues, "it would be necessary to acknowledge in the registry the existence of the three subsections of the breed, standardize within these types, stop crossing between the types, and close the stud books."
Thomas sees the current policy of the American Bashkir Curly registry as essentially a "coat registry." To become a "breed registry" it needs to register only horses with the dominant gene for curliness or at least not allow the recessive-type Curly to be used as Curly breeding stock. "The continuation of crossbreeding," cautions Bowling, "could virtually dilute out the more unusual aspects of the gene pool."
According to Thomas, the response from Curly Horse owners, breeders, and aficionados to the CS Fund report has been positive. "There is some interest in reorganizing the registry as well as starting a new one to reflect some of what we found out, and a Curly Horse Foundation has been founded to identify and conserve the American Curly Horse." The foundation has created a technical committee on which both Sponenberg and Bowling have agreed to serve. Its goals are to conduct and fund research about the Curly Horse and develop breeding and education programs to preserve the breed.
For its part, the CS Fun has learned valuable lessons in researching genetic roots from its study of the Curly Horse, and the nonprofit organization plans to produce a handbook for others interested in conducting similar studies. The CS Fund is considering another "roots research" with the bronze turkey, a rare poultry breed. Though the organization still owns two Curly Horses and will continue to track the breed's progress, it has called a halt to its breeding program, leaving the Curly Horse's fate in the hands of the owners and breeders. Fortunately, the foundation's study has taken some of the guesswork out of the tricky business of saving an endangered breed, replacing good intentions and chance with scientific fact.