Speaking of Secretariat..
When Secretariat was put down the autopsy showed that his heart weighed close to 22 pounds,the average Thoroughbred heart weighs 9 lbs. Secretariat's heart was all in porportion, not a mutation.
Geneticist Marianna Haun, among others, discovered that horses carry a gene for a large heart. It is passed through the X chromosome in the mare. Measurements of more than 400 horses with a ECG has found that the X-Factor is 100% consistent. It is possible to track the large heart from sire to daughter to granddaughter and grandson and to great granddaughter and great grandson. The heart scores on certain lines are 100% consistent. These lines come from Princequillo, War Admiral, Blue Larkspur, and Mahmoud.
We obviously know that Secretariat possessed the large heart gene. His heart was larger than any other TB on record. And we know that he got his large heart from Princequillo. A horse's heart is measured by a electrocardiogram and given a "heart score". That phrase was coined only 40 years ago by an Australian researcher named Dr. James Steel. In his research Dr.Steel ranks heart scores according to size. A score of 103 is considered small. A medium size heart is scored from 104-116. 117-120 and above is considered large. The Largest heart in his study was from the Thoroughbred Champion Key to the Mint. He carried the Princequello heart, and rated a heart score of 157-160. Most of Princequello's hearts were between 147 and 160. The three other "superhearts" were from War Admiral, Blue Larkspur, and Mahmoud. They had a heart score of 140-150. A heart score of 140 and above is considered very large and generally found in very successful racehorses.
Marianna Haun says in her book "The X Factor" that even though there is no heart score on Secretariat, based on the weight of his heart at autopsy his estimated heart score would have been 180. There has not been any heart score even near that size. She also states that if Secretariat's heart hadnt been so far out of the norm, they might not have ever discovered what they have about the genetic mutation that produces a high performance heart.
Just until recently it was thought that the sire was the one responsible for his offspring's success. The racing industry has judged a sire by his male offspring for hundreds of years. Great Thoroughbreds were thought to be busts because their sons never produced winners. But the large heart is passed to the foals by the dam. The TB Weekend Surprise is the daughter of Secretariat. Weekend Surprises' dam was Lassie Dear. She produced all winners, including her daughter who produced Horse of the Year A.P.Indy and Summer Squall. The exception to this however was ManO'War, who was fortunate enough to be bred to a mare whos heart was actually larger than his own. The mare was Brushup and she produced War Admiral. Seattle Slew, Cigar, and Silver Charm all have that heart line.Therefore ManO'War was considered a great sire, although it was his dam that passed on the large heart gene.
Throughout my research I have discovered that ManO'War's trainer Louis Feustel, never would let the jockey give him full rein. His reasoning here was to save his horse and not push him if not necessary. ManO'War did possess the large heart gene but I feel that even if he was given full rein he could not have maintained the stamina that Secretariat possessed. Through the strategies of Louis Feustal, ManO'War's legacy is cemented forever. The interesting thing about Secretariat is, in the Belmont, Jockey Ron Turcotte said he was along for the ride. The horse did everything on his own. He set a new world record that still stands, he beat extremely good competition by 31 lengths, and won the Triple Crown. We all wonder what Secretariat could have done if he was actually "asked". Like ManO'War before him Secretariat's legacy is cemented in history. Secretariats' rival in all three Triple Crown races was Sham. Sham's heart was weighed at autopsy at 18lbs. The second largest on record. He lost to Secretariat all three times. At the '73 Belmont, Sham tried in vain to keep pace with Secretariat but to no avail. Even with an 18 pound heart and tremendous will to beat his rival, Sham could not muster the stamina. Sham finished last and never raced again.
Secretariat.com
wil.
