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The large Heart Gene and the X factor explained.
The following information is derived from the American Saddlebred magazine and from Marianne Haun’s two books on the subject.
Author Marianna Haun wrote two books on the subject of the large heart. In her studies she determined that the large heart existed in 28% of the current Saddlebred population i.e. 28% of each foal crop. The large heart is a genetic mutation that is found on the sex linked X chromosome and is passed from father to daughter and from daughter to sons and daughters. It is not passed from fathers to sons. In order to get the heart a stallion has to have a dam that had the heart. This gives a new meaning to the importance of the bottom line in a pedigree! However ,only an actual physical measurement can guarantee the large heart is present. A pedigree is only an indication the horse may have the large heart
Double and Single copy mares A double copy mare has inherited the large heart gene from both her sire and dam. A double copy mare transmits the large heart to both her sons and daughters. A single copy mare is more complicated. She may transmit the single heart she carries to 50% of her foals. The only way we can tell is based on the performance of her offspring.
The only other way you can tell if a single copy mare passed the heart on is if you are looking at her and her foal and are able to watch them in motion. If their heads are similar in conformation and their front end conformation causes them to move in a similar manner, the dam has probably passed that heart onto that foal.
Example -See picture below of double copy mare Canyonleigh Vanity’s Pride and her filly foal Inspirations Cover Girl stride for stride.
Large Heart genes and their importance to breeding good horses.
Of course this is not an exact science and without pictures and electrocardiogram or ultrasound readings there is no way of determining the facts for sure. However, by looking at a pedigree you may ascertain if the horse could likely have a heart gene inheritance.
A large heart is desirable in any horse that is bred and trained for any kind of performance activity that requires a lot of stamina.
The sport of Endurance which is one of the elite sports where your horse would most certainly benefit from having a larger heart than most.
The importance of a large heart in the racehorse goes without saying and two of the most famous racehorses in the world (Phar Lap and Secretariat ) were found to and actual physical evidence proved that they had larger than normal hearts. The average horse heart weighs in a 8.5lbs. Secretariats weighed 22lbs Phar Laps weighed almost 14lbs |
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