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HERDA Traces to Poco Bueno

 

It isn’t just a matter of identifying the gene, says Winand. Once that has been accomplished, the researchers face the task of perfecting the test. “You must optimize the test to ensure specificity (thus avoiding any chance of false positive or false negative results)”.

In the meantime, the first line of defense by horse owners is to avoid breeding a known carrier to a known carrier. A horse that is an HC gene carrier is never afflicted with the disease. It is clinically normal and shows no signs of the disease. However, when two carriers are mated, there is a 25% chance the offspring will have HC.

Under the genetic law of averages, here’s how it works, according to the two researchers. When a normal horse (one that is not a carrier) is crossed with a carrier, 50% of the offspring will be carriers and 50% will be normal. When a carrier is crossed with a carrier, 50% of the offspring will be carriers, 25% will be normal and 25% will be afflicted (can develop the clinical signs of HC). When an afflicted horse is crossed with a carrier, 50% of the offspring will be carriers and 50% will be afflicted. When an afflicted horse is crossed with a normal horse, 100% of the Carrier status is established when a stallion sires an HC-afflicted offspring or when a mare gives birth to an HC-afflicted foal. When properly diagnosed, it only takes one afflicted foal to establish carrier status, Rashmir and Winand say. There was a time in the past when some in the cutting horse industry referred surreptitiously to HC as the Doc O’Lena affliction because a number of HC horses carried his bloodline. Doc O’Lena was indeed a “prolific carrier,” says Rashmir, but it went beyond that--back to his grandsire Poco Bueno and beyond.

It has been established, say Rashmir and Winand, that the recessive gene was passed on to Doc O’Lena through his dam, Poco Lena, rather than through his sire, Doc Bar. There is no evidence that Doc Bar was a carrier, they say. Poco Lena had only one other foal, Dry Doc, and he, too, was a That, says Winand, is unfortunate. Under the genetic law of averages, there was only a 25% chance that both would be carriers.

The Poco Bueno bloodline begins with a mystery horse, according to American Quarter Horse Association (AQHA) pedigree records. The horse was named Traveler, believed to have been foaled in the late 1800s, and he literally came out of nowhere. No one has a clue as to what his pedigree might be.

The late Robert Denhardt, author, and one of the founding fathers of the American Quarter Horse Association, described Traveler thusly in his book, Quarter Horses: “Traveler’s history has been traced back to Eastland County, Texas, where he was working on the railway. He was just a sorrel work horse in a large remuda owned by the contractor. It has never been adequately explained just how it happened that a stallion was allowed with the horses, but there was no disagreement on this part of the story. Traveler was not a young horse when he left the railroad--his age has been estimated between eight and 10. He had to be broken to the saddle, even though trace-chain marks showed on his side and collar marks on his shoulders. He had been worked plenty, but not ridden. According to one old-timer, he pitched terrifically, but showed great intelligence and soon quieted down.”

Despite his age, Traveler raced successfully. However, it was as a sire where he shined. He sired an excellent racehorse in Little Joe. That stallion in turn sired Zantanon, and Zantanon sired King, the sire of Poco Bueno. Poco Bueno was born in 1944. King and Poco Bueno became legends in their time, and in the breeding shed they sired outstanding cutting and performance horses.

One of the greatest sons of Poco Bueno was Poco Tivio, foaled in 1947. The researchers say that he was a carrier of the HC gene. Poco Tivio became well known for his excellent producing daughters, many of which were bred to Doc Bar. It was a magic cross, with many of the offspring becoming champions and big money winners in the cutting arena. Unfortunately, under the genetic law of averages, many of them also would be HC gene carriers.

It wasn’t long before cutting horse enthusiasts reasoned that if a little of the Poco Bueno bloodline through descendants like Poco Tivio and Doc O’Lena was good, a lot might be even better. Through the years there has been a good deal of inbreeding, which has allowed HC to flourish in the gene pool reservoir and now is manifesting itself with greater A check of the 2004 Quarter Horse News Stallion Register, Rashmir says, reveals that out of the top 100 cutting horse stallions, lifetime, based on earnings of offspring, 14 are known HC “That,” says Winand, “is just the tip of the iceberg. This thing (HC) is going to mushroom in the next several years, and there is no way to stop it. Because of the popularity of sires that are (or were) carriers and the use of assisted reproductive technologies (shipped cooled and frozen semen, for example), it is likely that the HC gene is present in thousands of horses.”


“We didn’t have that many cousins carrying the HC gene being bred to each other in the past,” says Rashmir. “Now we do.” Winand says that another study, also based on statistics published in the 2004 Quarter Horse News Stallion Register, reveals that between 1998 and 2002, some 1,241 offspring of HC carrier stallions were sold at public auction for $26,749,650. One-half of those offspring, based on genetic law of averages, she says, also are carriers.

Winand emphasized that other disciplines besides cutting are involved in these bloodlines--reining, working cow horse, and even pleasure horses. “It is not just a problem with cutting horses,” she says. “It can involve all disciplines when “It’s not the horses’ fault,” says Rashmir. “It’s the way we have bred them. Many of these horses have been, and are, wonderful athletes and, though they are carriers, have no outward signs of the disease. Breeders are going to have to take responsibility for their decisions and not breed known carrier to known carrier.”

Mississippi State University has taken a step to facilitate that process. Horse owners can send pedigrees involving potential matings to Rashmir, and she will analyze them and seek to determine the degree of probability of the offspring inheriting either the gene, or the disease itself. A fee of $25, which goes directly into the HC Research Fund, is charged. The address is College of Veterinary Medicine, P.O. Box 6100, Mississippi State University, Mississippi State, MS 39762.

With Rashmir’s help, the first step in curtailing spread of the HC gene pool can be taken by individual breeders. The American Quarter Horse Association is concerned about HC, says Gary Griffith, executive director of registration for AQHA. He says the announcement by Rashmir and Winand, to his knowledge, is the first public revelation concerning the Poco Bueno bloodline being the primary reservoir for the He said that AQHA is funding research at the University of California, Davis, which is attempting to identify the gene responsible for HC. Hopefully, such research, he says, will provide a simple genetic test that will identify HC carriers. “All of the information stemming from research into this problem will be passed on to the appropriate registry. (AQHA) There is good news for owners of Poco Bueno-bred horses -- not all of them are HC gene carriers. Many are not. The goal is to determine which ones are, and avoid breeding carrier to carrier.
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