Every year since 1978, we’ve packed the stands of Churchill Downs, and stared intently at television screens watching and waiting…  will THIS be the year?  A Triple Crown winner has continued to elude us, but our hope hasn’t waned.  Every year is a new year, and a new chance at history.  That history begins with the Kentucky Derby and a band of broodmares known simply as “Royal Mares.”

When we think back to known Triple Crown Winners, names like War Admiral (1937), Whirlaway (1941), Secretariat (1973), and Seattle Slew (1977) come to mind.  What we often may not consider, is what did these champions have in common?  The easy answer, and one commonly offered without explanation, is “the x-factor.”  It’s an expression that’s often tossed around when referring to people/places/things that just seem to have that certain something about them.  In this case, it refers to a documented gene mutation located on the x chromosome, causing a larger-than-average heart in horses.

The X-Factor is often traced back through the lineage of Eclipse, born in 1764 with a remarkable British racing history, and even more remarkable history as a sire.  But, according to Horse Nation’s in-house historian Lorraine Jackson, it goes back further than Eclipse, to a grey stallion born in 1690, also of British descent, named Hautboy.  While these stallions have most likely been genetically gifted this trait from their dams, it also meant that they were then only able to pass the trait on to their daughters.



All descendants of Eclipse; Princequillio, War Admiral, Blue Larkspur and Mahmoud were found to have larger-than-average hearts.  Where in the case of Hautboy, there were hundreds of nameless, “royal mares” bred by Lord James D’Arcy in the1660’s, who was appointed to oversee the Royal Stables and expand the breed of racing horses for England, making more specific lineage impossible to trace.

war admiral

War Admiral






Seattle Slew

The heart score was developed over 40 years ago, believing that a large heart correlated to athletic ability.  However, the actual gene hasn’t been identified, nor it’s mode of inheritance been determined, lending itself to the idea that the condition may be influenced by multiple genetic factors.  Eclipse, when he passed, was recorded as having a heart weighing in at 14 pounds, double what’s considered “average” for a horse.  Secretariat was also noted as having a 14 pound heart.

Most of our modern contenders carry Northern Dancer and Secretariat bloodlines known for the “X-Factor,” but it isn’t clear if the gene is present in any of them at this time.  Dortmund appears to be one of, if not the largest in the field at 17hh, but does his overall size indicate a heart to match?  Will this year’s winner need an oversize heart, or will figurative heart be what carries him across the finish line first?

Who’s your pick?  Just for the Kentucky Derby, or for the whole shebang?  Only three days until we find out who the next “one to watch” will be!

May 2, 2015

May 16, 2015

June 6, 2015


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