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Legendary Hearts of Horses

Heart is a word we have many expressions for. We use them to describe moments, conditions and events our lives. Words like heartfelt, heart of the matter, follow your heart, from the bottom of my heart, having a heart to heart…Of course, there are the darker elements; heart of darkness, change of heart, halfhearted, coldhearted…it’s no wonder we’re fascinated with the heart of every horse, especially the extra large hearts. Following the genetic expression of the equine large heart gene throughout history and before, uncovers that heart, while expressed physically in various sizes, is indelibly interwoven with Love, beauty, inspiration, courage and sacrifice. It’s an ageless story about the tangible and intangible qualities of Heart itself.


On June 9th, 1973, Secretariat gave us something so magnificent; something so sublime and something so truly remarkable.

With every stride Secretariat took during the Belmont Stakes – the third and final leg of the American Triple Crown – people knew they were witnessing the greatest performance in all of Belmont’s history.

With 1/4 of a mile to go, he was 14 lengths in the lead. Coming out of the turn for home, he was 18 lengths in the lead. People watching on television heard words infused with unmitigated awe: “He’s moving like a tre-mend-ous machine!”

And we wept. We wept long before the race was over because of his courage, his pride, his freedom. His statement to all of us: I never give up, I never give in, and I do my best every single Moment.

Secretariat finished the 1973 Belmont Stakes an astonishing 31 lengths ahead of his competitors, in a world record time of two minutes and twenty four seconds. He didn’t hurt, harm or cut anyone else down to win, nor was he shy or ashamed of winning. For Secretariat, those ridiculous notions things didn’t exist.

It was phenomenal. Awesome. Indelibly etched in our consciousness, and a instance that has not been duplicated…ever.

Secretariat was born on March 30, 1970, and died on October 4, 1989 at only 19 years old. There were such hopes that the world would see more horses just like him after he went to stud, but that dream was never realized. He was enigmatic and unique. He was not only an equine superstar, he was a horse of the people.

While he conquered tracks in the USA and Canada with his phenomenal countenance and blazing speed, his image was featured in iconic publications like Sports Illustrated and Time Magazine. Movies and documentaries sprouted, inspired by that special something he naturally possessed. He had ‘it’…that undefinable, indefatigable courage and grace imbued and powered by the Almighty Source of all that is. He captured our hearts with his own, and he fired the imagination of cynical experts, fans and common folk alike.

Just how did he run so fast, typically coming from the back of the pack and annihiliating the field of runners that opposed him?

One of those reasons, was plainly expressed by Dr. Thomas Swerczek DVM PhD, who preformed his autopsy, “It was the biggest [horse] heart I’ve ever seen.” (Bonner, 2004) And it was perfectly healthy.

As he lifted the ‘mega-heart’ out of Secretariat’s body, you could imagine people gasping in stunned silence, just as they did during his racing career.

An average horse heart is about 1% of total body weight for a Thoroughbred (other breeds vary). Most horses average a heart size around eight and a half pounds, however, Secretariat matured at around 1200 lbs. For a horse this size, a normal heart would mathematically and theoretically average twelve pounds…even still Secretariat’s heart weighed twenty-two pounds…

Demonstrating the super large heart, and suggesting the room it needed inside a horse's body compared to a normal sized heart.
Secretariat needed a custom girth to reach the billets on each side of his saddle.

This is like the difference between a roaster chicken and a Thanksgiving turkey! Imagine the main arteries leading away from it to supply the body, imagine the size of the major veins bringing the oxygen depleted blood back to it.

Imagine this heart muscle was strong; its walls thick, and its size giving it twice the capacity of a normal heart.

Just one beat of Secretariat’s heart accomplished the work that required two beats of a another horse that was comparable to him in height and weight.

Note: It doesn’t take much to rob a horse of his potential, big heart or not. Improper nutrition, improper handling, negligent mare care, any number of things may conspire to hold back any individual.

To set a Soul like this free, it takes tremendous skill; knowledge combined with love and patience to nurture and coax the horse into an understanding of what is expected…so much so, that he takes this information and owns the knowledge for himself. He masters his environment. He takes the lot that has been given to him, and shows his best to the world, on the world’s stage. Without reservation. Without doubt. He accepts the confines of human rules and expectations, and courageously expresses himself. He becomes our hero. He humbles and inspires us with his generosity, his Spirit, and his countenance. This is a Legendary Heart, one that shows us what can be done. One that tells us to have courage, and live life not in a dream world, but in a real world; a hard world. To dig our deepest without fear. Until you do that, you won’t know what you are capable of…

Clearly, this wonderful horse was surrounded by people who taught him their system respectfully; leaving his Spirit, his willpower and eccentricities, and his own determination intact. For Secretariat’s part, it is safe to say that he was nurtured from the day he was conceived, and brought to his full potential by careful, compassionate, and knowledgeable people.

But how was it that he had such a big heart?

Following the remarkable discovery of Secretariat’s heart, the renowned equine cardiologist Dr. Fred Fregin, and researcher Marianna Haun embarked on the large heart trail. The work was twofold: first, compile a database of horses and record their statistics using ECGs and ultra sound technology, and second; combine that with extensive pedigree research.

It was theoretically determined that the trait for the equine large heart was carried on the X, or female, chromosome, which is why it is called the X Factor – and in following this gene to its possible roots, the X factor begins to tell an epic story…

Following the ‘X-trail’ and stepping further back into time, there was another horse; one that was in the pedigree of Secretariat hundreds of times, and had a story of his own.


Eclipse At New Market With Groom. Painting by George Stubbs (1724-1806). Public domain.
(he was born during a solar eclipse and was so named on April 1, 1764)

Eclipse’s white face punched through a thick, chilly fog with the suddenness of a violent storm. He delivered an unmistakable message: I am unbeatable.

‘Eclipse first, the rest nowhere’ became the horse’s motto. Strong and full of fury, Eclipse snapped at his adversaries, never allowing any one of them to pass him.

Eclipse was a raging flame, willful and incorruptible. Whip and spurs were absent from the jockey’s fittings, as the horse would never tolerate such garishness.

Like Secretariat, his performance improved with distance. While his competitors were burned up by fatigue, Eclipse won his challenges with ease. It was more than just a victory, it was a reckoning. Undeniable, and unwavering. Consistent and crushing.

During the 18th century, races were typically two or four miles long. Historical accounts convey that Eclipse eased over the finish line with a rumor of other horses having been entered in the race. It was as if they participated in an entirely different event.

Eclipse was not the first undefeated champion of the newly formed British Thoroughbred, but he was the most celebrated. Eclipse was a phenomenon, carrying a veil of superiority that was respected and feared. He was a legend in his own day, acquiring a loyal base of supporters whose endless chattering filled the air for years to come.

He was an egotistical horse, unwilling to tolerate forceful actions originating from man or beast. His own integrity was paramount, his dialogue intense. This was his countenance both on the track and off. He was a horse of magnificent talent and tremendous will; one who demanded respect – one who would not suffer anything less.

This was a horse whose individuated spirit – his soul – was here to tell people, ‘I will perform for you, but you must ask…you must seek my willingness. I have my own opinion, I have my own way. Ask, and I will give freely. Take without permission, attempt to force, and I will not have it. I will fight.’

It must have been such a thrill to have watched Eclipse race during the nascent development of the breed known as the Thoroughbred. Startlingly fast and undefeated in 18 events, the chestnut colt was a harbinger of Thoroughbred greatness.

Upon his death on February 26, 1789 – at almost 25 years old, he was examined by Monsieur Charles Vial de St. Bel, who recorded the session with meticulous detail. Among Eclipse’s measurements, it was noted that he had a heart that weighed fourteen pounds…

Excitement prevailed for Fregin and Haun, as the pedigree trail sparked by Secretariat led to Eclipse himself. The ‘X-factor’ theory was shaping up on both ends of history. Both were gifted super horses, powered by hearts that made them legends; governed by an insatiable and unconquerable spirit of the wind.

The equine large heart story could begin and end here. But of course, it is not that simple.

There’s a problem. A big one…

The idea that a single genetic mutation occurred either at Eclipse’s conception or during his fetal development endowing him with a larger than normal heart was posited. This ‘spontaneous mutation’ would mean that only Eclipse would have possessed this super heart, and therefore, he would be the only one able to pass this trait to his offspring. It makes the theory easier to grasp, but quite a stretch given the magnitude of the equine canvas.

Perhaps epigenetic conditions were ripe, but why this one horse? Why Eclipse when there were millions of horses on Earth at that time and expentionally more in the past who could have carried the trait and experienced conditions and opportunities to express it?

A study of horses ‘before’ the official breed of ‘Thoroughbred’ was needed, but funding of this kind wasn’t available. Like the proverbial chicken and the egg, this dilemma simply takes on different clothing; which came first — the large heart gene, or Eclipse?

Note: Continuing their research within the Thoroughbred breed (still a valuable pursuit), data pointed toward a descendant of Eclipse – a mare named Pocahontas born in 1837 – to whom they attributed the proliferation of the large heart gene in Thoroughbreds. Pocohontas’s son Glencoe was famous racehorse and successful sire in Britain. However (fortuitously), he was imported to the USA, where he had an astounding influence on several breeds.

Following the equine large heart trail also includes Eclipse’s parentage which has embedded clues: his undefeated maternal grandsire Regulus, and the qualities by way of these x-factor female components…

Adhering to the theme and logic that only mares pass on this trait, three mare lines stood out in my personal research. Of Regulus’s heritage, two of the Royal mares in Queen Anne’s stable: Royal mare number 6 and Royal mare number 2 are of extreme interest.

They had produced horses like Hautboy, Snake, and Bald Galloway who became prominently established in the pedigrees of the best horses in Britain and the New World. It is important to keep in mind that the Royal mares (many of whom sported significant oriental blood) were bred to many oriental stallions, including Lister Turk, White Turk, and the Barbs like Fenwick Barb and St. Victors Barb.

There were also the daughters of Brimmer. Brimmer was a champion racehorse and sire by ‘Darcy’s’ Turk out of a Royal mare of unknown origins. However, because he was such an early horse little has been documented, but it is known that his ancestry was primarily Turkish and North African…

The Byerley Turk, an oriental stallion from the Ottoman Empire, was the earliest of the three recognized foundation sires for the British Thoroughbred. Royal and other oriental mares produced incredible horses when their blood was mixed with this propotent stallion.

For example, when Byerley Turk was crossed with the Taffolet Barb mare born of another ‘Barb’ mare by a Turkish stallion, one of the most important female families of Thoroughbreds was ‘born’, stretching its influence into to modern days.

“Still the most populous female family, with a 2010 Epsom Oaks winner, the fortieth tracing to its founding mares since the race was first established in 1779. Some of the most renowned mares in the history of the thoroughbred, and many of its most influential stallions, are members of Family 1.”, accessed 9-12-2020

“Of the many Family 1 mares of significance to the breed, the most important is Julia (1756, by Blank), with four generations of high-class race mares and broodmares — many of them taproots of various branches of the family.”

ibid., accessed 9-12-2020

Julia had a great deal of Barb/oriental blood running through her veins. She was the daughter of the incomparable ‘Bonny Lass’ (great granddaughter of the Byerley Turk) and Blank, a son of the Goldolphin Horse aka Godolphin Arabian.

The Godolphin Horse reinvigorated compactness, stamina and speed…a formula that was coveted and desirable, especially as the foundation for the Quarter Horse and spilling into horses like Man O’ War and Secretariat.

Centuries earlier, the blood in these Royal mares had provided the foundation for breeds such as the Connemara and the Irish Draught horse. They were known for their speed and agility. These sturdy, athletic horses were used by Robert the Bruce in his fight for Scotland’s independence…while King Edward tried to prevent these valuable beasts from ever getting into the possession of his enemies (a similar sentiment influenced the US Government in their war against the Native Americans).

The story continues…

PS: Another large heart horse:

Phar Lap

Phar Lap with jockey Jim Pike riding at Flemington race track c 1930
photo by Charles Daniel Pratt, 1893-1968 / Public domain

During the 1930’s, researchers in Australia identified a departure from the norm when they witnessed the size of Phar Lap’s heart. Phar Lap, Australia’s ‘Wonder Horse’, was a very large horse, with a very large heart seemed to have been bypassed by the large heart researchers.

Forty seven years before Secretariat was born, a little foal came into being named Phar Lap. During his racing career, he had become a true legend; cantering rather than galloping across the finish line, usually with several lengths to spare.

Equine Large Heart research had begun almost 50 years earlier in a different country!

After his passing in 1932, his body was preserved, and his heart revered. The phrase “a heart as big as Phar Lap’s” signifies strength, power, and generosity.

Physically, his heart weighed 14 pounds, and is on display at the National Museum of Australia.

Phar Lap’s Heart
AYArktos / CC BY-SA (

His pedigree does include Eclipse (and Pocahontas) in X positions, however, there are far more Godolphin Horse and Byerley Turk daughters sprinkled throughout those ‘influential and essential’ theoretical X positions. If cumulative effects, inbreeding coefficients, probabilities and other mechanisms have their influence, then Phar Lap’s blood would be an advocate for the amount of ‘varied spice in the sauce’, rather than a few chance peppercorns.

Continue reading! The next chapter goes further back, to the origins of the Thoroughbred…

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