What Makes a Great Racehorse

Living in the horse capital of the world, Lexington, Kentucky, it is not rare to find great racehorses. From the Kentucky Horse Park, to several racetracks such as Keeneland, to the numerous horse farms, it is evident that Lexington is well known in the horse industry. The competitive racing of horses is one of humankind’s most ancient sports dating back to 4500 BC, and is the second most widely attended U.S. spectator sport (Parker). While the majority of the public may be more interested in only profit from the racing of horses, others are more intrigued by the horses themselves and what makes them successful performers on the racetrack. The anatomy of a horse is one of many explanations to success in racing. I believe that the size of a heart is considered to be the most important factor in a racehorse’s performance, and that the size has a direct relation to the genetics of a horse. It has been said that, “Ever since the first rider challenged another rider to see who had the faster horse, horsemen have described the fastest runners as having “great heart” (X-Factor 13). The term originally described a horse’s charisma and its determination to cross the finish line with passion. However, the term ‘great heart’ took on a whole new meaning after an autopsy procedure performed here in Lexington, Kentucky.

Many have heard of Secretariat, a Kentucky bred horse known worldwide for his success in racing. An article by ESPN stated, “Secretariat was the winner of the 1973 Triple Crown and is widely considered to be one of the greatest Thoroughbred race horses of all time. His times in the Kentucky Derby and the Belmont Stakes set records that still stand today.”  These  accomplishments say a lot about the athleticism and greatness of Secretariat. He was not just an ordinary horse. In fact, in 1999, Secretariat was ranked the 35th greatest athlete of the 20th century by ESPN. His placement on the list was significant because he was the highest-ranking non-human on the list. Maryjean Wall, a horseracing writer for the Lexington Herald Leader, wrote,  “Secretariat was a living flame, a strikingly handsome chestnut colt whose charismatic qualities quickly won him worldwide acclaim” http://infoweb.newsbank.com/iw-search/we/InfoWeb?p_product=AWNB&p_theme=aggregated5&p_action=doc&p_docid=0EB739B8044CEFB0&p_docnum=1&p_queryname=6

After Secretariat’s unfortunate death, it was discovered that his heart was almost three times the size of an average horse. Dr. Thomas Swerczek, my grandpa, works at the University of Kentucky and has spent many years in equine veterinary sciences. He performed the autopsy procedure on Secretariat back in 1989. In a Sports Illustrated article, William Nack wrote, “Just before noon the horse (Secretariat) was led haltingly into a van next to the stallion barn, and there a concentrated barbiturate was injected into his jugular. Forty-five seconds later there was a crash as the stallion collapsed.” Secretariat was in so much pain that the only reasonable thing to do was put him down. No one knew the cause of his pain and therefore nothing could be done to keep the Thoroughbred alive and well. Nack continued, “His body was trucked immediately to Lexington, Kentucky, where Dr. Thomas Swerczek, a professor of veterinary science at the University of Kentucky, performed the necropsy. All of the horse’s vital organs were normal in size except for the heart.”

In the same article, Nack quoted Swerczek saying, “We were all shocked. I’ve seen and done thousands of autopsies on horses, and nothing I’d ever seen compared to it.” Dr. Swerczek said that the heart of the average horse weighs about nine pounds and Secretariat’s heart was about twice the size that. It was the largest equine heart he had ever seen. Swerczek noted, “it wasn’t pathologically enlarged. All the chambers and the valves were normal. It was just larger. I think it told us why he was able to do what he did” (Sports Illustrated).

In a recent interview with my grandpa I asked him about that day when Secretariat was brought in for procedure. The first thing he told me was “I almost missed the discovery of the large heart.” Since Secretariat was such a beautiful animal, Dr. Swerczek said he did not want to mutilate the body at necropsy, but rather only determine the cause of death. He informed me that Secretariat was suffering from a severe disease condition called laminitis, and further explained to me that the disease “is an inflammation of sensitive layers of tissue inside the hoof between the bone and the hoof wall.” My grandpa told me that because of the severe laminitis, Secretariat had to be put down in order to stop his intense suffering. Dr. Swerczek said he not only found that the laminitis affected all four feet, but that lesions were very severe. In addition to the feet, lesions were found in the kidneys and liver.

Most all great Thoroughbred horses, like Secretariat, are insured as they are valued in the millions of dollars. Dr. Swerczek said that since he was satisfied that he found the cause of Secretariat’s illness, he did not want to further dissect the body because the owner wanted to keep the body intact as possible for burial at Claiborne Farm, located in Paris, Kentucky. My grandpa told me that the resident Veterinarian at Claiborne Farm, where Secretariat stood at stud, was Dr. Walter Kaufman. The term stud simply refers to a farm where horses are kept for breeding, and stood at stud means the horse is available for breeding. Kaufman, like my grandpa, provided for the veterinary care of Secretariat since his arrival at Claiborne to stand at stud at the end of his racing career. As Dr. Swerczek was completing the autopsy, Dr. Kaufman asked my grandpa, “I wonder what Secretariats heart looks like.” This led to Dr. Swerczek deciding to further dissect Secretariat’s thoracic cavity and remove the heart. My grandpa said, “It was then that Secretariat’s large heart was found and it was obvious why he was one of the greatest racehorses of all times.” My grandpa has performed necropsies of several thousand Thoroughbred horses, and no other horse had the heart the size of Secretariat’s.

Scientists made the assumption that Secretariat’s heart size was a contributing factor to his excellence in racing. Their theory was proven even more correct in 1993 thanks to another Thoroughbred horse named Sham. An ESPN article about sham stated, “Sham may be one of the unluckiest horses to have ever galloped over a race track. He was lucky enough to be blessed with incredible talent but had the misfortune to have been born in the same year as perhaps the greatest thoroughbred of all time. That horse of course is Secretariat.” Sham and Secretariat were huge rivals who both competed at Belmont Stakes in 1973 when Secretariat won the Triple Crown. Earlier that year at the Kentucky Derby, Sham finished 2 1/2 lengths behind Secretariat, however he ran the second fastest Kentucky Derby ever that day. http://www.horseracegame.com/community/content/blogs/espnsports/16-07-2009/sham-underrated-superstar

After Shams death in the year of 1993, my grandpa also performed the necropsy on Sham. He found that Sham’s heart was the second largest heart he had ever seen in a Thoroughbred racehorse. It weighed 18 pounds compared to Secretariat’s heart weighing 22 pounds. My grandpa told me that the third largest heart he discovered at necropsy was from another great racehorse named Key to the Mint. However, it weighed much less at 16 pounds.

The coincidence of two great racehorses with two huge hearts gave way to Marianna Haun’s book The X Factor, which discusses the relationship between inherited heart size and racing performance. After years of conducting heart measurements, collecting blood samples for DNA analysis and charting autopsies of Thoroughbreds from Kentucky to California, Haun came to a conclusion. The findings were able to prove that the inheritance of heart size is linked to the X chromosome. This means that the genes related to heart size are passed from stallions (male horses) to their daughters and then to the next generation. Dr. Gus Cothran, a geneticist at the University of Kentucky’s Equine Research Center, hypothesized that if the sex linkage was true then the characteristic was most likely a genetic mutation from a single source that could have been passed down from hundreds of years ago. After several months of research, a genetic link was found on the X chromosome line between Secretariat and Eclipse, another great racehorse, with more than 200 years separation through the female horse, Pocahontas, who was born back in 1837 (X-Factor 54).

Almost every finding has at least one contradiction. Dr. Swerczek informed me all about the argument involving steroids. With athletes there is a controversy that the use of anabolic steroids improves athletic performances in several sports, including baseball, bicycling and track as well as others. These steroids are now banned for use in humans in order to make sports fair for all athlete participants. In racehorses, these anabolic steroids have been used for years. The reason is to increase the growth and muscle mass of developing horses. These steroids have a major effect on increasing the muscle mass of humans and animals. Currently, like with the human athlete, there is a move to make these steroids illegal for racehorses.

It is not known if these steroids increase the muscle mass of the heart like they do with the skeletal muscles. Some people feel that the large heart in some racehorses, like Secretariat and Sham, may have been due to the use of steroids.  This is important as horsemen who are against the use of steroids in racehorses feel that they may have a harmful effect on the horses. In other words, outstanding racing performances may be due to the use of steroids, and not due to the genetics of the horse. This is important to many people involved in the horse industry because integrity of the horse breed is lost. Racehorses with outstanding racing performances due to the use of steroids would not pass on their  abilities to their offspring, and would  have a negative effect on breeding stock. Another reason why there is a move to have these steroids eliminated in racehorses  is because the betting public has lost confidence in the truthfulness of the sport . The public uses past histories of great racing lines of the purebred breed to predict which breeding lines will make great racehorses as well as a good breeding stock.

It is for these reasons why the large heart in some racehorses is debatable.  It is not known for sure at this time if steroids have caused horse’s to produce a larger heart because there is not enough evidence to prove this. However, the X-Factor proposal has much more scientific proof making it the only acceptable reason for the heart size.

As proven, a horse’s large heart size is an advantage in racing. However, the health of the heart, either large or small, is just as important. According to Dr. Herb Maisenbacher, a clinical assistant professor of cardiology, heart disease is the third most common cause of poor performance in horses. An article found in Holistic Horse quotes Maisenbacher stating, “If a horse has an underlying heart disease, stress or work can negatively affect it, as the heart cannot function efficiently and congestive heart failure, or even death may occur.” http://www.holistichorse.com/Behavior/the-equine-heart-beyond-the-x-factor.html This shows how important the health of a horse’s heart is, especially in the racing world. My grandpa informed me that when examining Secretariat’s heart, it was evident the horse did not suffer from any sort of heart disease, which was another bonus to his athletic abilities.

Todd C. Holbrook, a professor of equine medicine, wrote about the equine heart and said, “The impact of heart size on performance is supported by relative heart sizes in famous human and equine athletes. One multiple Olympic champion distance runner had a heart mass that was almost three times larger than predicted for his body size.” He then went on to talk about Secretariat’s heart size. It is evident here that not only horses, but humans too, can benefit athletically from a larger than normal heart. So why does a larger heart improve performance? The larger the heart is, the more blood it can pump. Cardiac output is the amount of blood pumped per minute, and when physical activity begins the cardiac output increases. Therefore, the volume of blood being pumped increases, and a larger heart will allow for a greater cardiac output, which is required to supply the muscles with oxygenated blood. All of this results in more energy and a stronger endurance. http://www.distanceriding.org/php/articles/health/TheHeart.pdf

As I mentioned before, the heart is the most important factor in a racehorse’s performance. The proof can be found in horse breeding.

Any breeder would want a horse with the athletic ability of Secretariat. After discovering that a horse’s heart size relates to their genetic make-up, breeders began to try and create that large heart gene. Luckily, it is possible to identify the largest heart line in todays breeding stock. This can be done by researching pedigrees, checking autopsy’s past and present, and by examining horses that are now in training as well as failed racehorses (X-Factor). Knowing that large hearts in horses can only be passed down through mares, the pedigree research is perhaps the best way to go about choosing horses to mate. By looking at a pedigree chart, one can go several years back and see what horses carry the large heart gene, and what horses have the potential to pass it on. An example can be found with Secretariat. Weekend Surprise was one of his daughters who produced A.P. Indy who in turn was the mother of Rags to Riches. Rags to Riches won the Belmont Stakes only a few years ago in 2007. Terlingua, Another one of Secretariat’s daughters, created Storm Cat and his daughter, Secrettame. Both of which are considered very good sires of sires. This genetic power has been passed down through the daughters. As imaginable, Secretariat’s sons were not nearly as successful. http://www.sport-horse-breeder.com/pedigree-study.html

However, just like racing, horse breeding consists of luck because of uncontrollable factors. Breeders cannot control the sex of the horse, which means there is never a sure chance in producing the large heart gene that can only be passed along the X-Chromosome. There are also other factors such as unknown diseases that disrupt the breeding process (X-Factor 192). When the correct horses are bred together with desirable traits and luck is on the breeder’s side, it is easy to create a foul with great potential in the racing industry.

These days, it is hard to separate horse racing from horse betting. Even though placing a bet for a certain horse to win may consist of a lot of luck, everything about the horse is taken into consideration. The heart of the horse is a major determination of what makes a champion on the racetrack. Thanks to Secretariat it has become possible to breed these champions to have ‘great heart.’

Link to partner: www.goodracehorse.wordpress.com

Additional Sources:

“Basic Horse Genetics.” Horse-genetics.com. Web. 09 Nov. 2011.

Haun, Marianna. The X Factor: What It Is & How to Find It: The Relationship Between Inherited Heart Size and Racing Performance. Neenah, WI: Russell Meerdink, 1997. Print.

Nack, William. “Pure Heart.” Sports Illustrated Vault. 04 June 1990. Web. 24 Oct. 2011.

Parker, Mike. “The History of Horse Racing.” Web. 15 Nov. 2011.

Swerczek, Thomas. Personal Interview. 12 Nov 2011.

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