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How are Racehorses, Bred? Tradition vs. Modern Science

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I always enjoy this time of the year seeing the foals, the future crop of racehorses, playing in the pastures. However, I never thought much of the process it took to get these foals here, so I started doing some research to learn about how racehorses are bred.

Thoroughbred stallions must “live cover” a thoroughbred broodmare for their offspring to become a registered thoroughbred racehorse, Quarterhorse broodmares can be either “live covered” or artificially inseminated.

The process of determining what stallion to breed to a particular broodmare is a complicated formula. Let’s look at this in more detail.

Racehorse breeding is a risky business.

It’s estimated that only 6% of racehorses earn enough money to cover their expenses and just a small fraction of these go on to win any significant money.


Owners and breeders try to increase their chances of success with superior breeding. In this article, we will look at both how racehorses are bred and what factors go into the decision to mate individual horses.

Thoroughbreds studs must “live cover” a mare.

The Jockey Club requires Stallions to “live cover” a mare for its foal to become a registered thoroughbred racehorse. http://www.registry.jockeyclub.com/registry.cfm?

Live cover: The live cover process begins with an examination of the broodmare. The veterinarian will keep a close eye on the mare watching for signs of ovulation. He may run a test to determine which day and time will make conception the most likely.

Once the mare has entered ovulation, she is brought to a select location for breeding by an experienced handler. Safety is paramount for all involved. After she settles into her new place, her tail is wrapped, and she is thoroughly cleaned. Next, a teaser stallion will be brought in to get her ready for breeding.

The stallion is brought to the breeding location and cleaned as well. If everything is right and all parties ready the stud is walked up behind the mare, and he mounts her. This process will only take a few minutes. Afterward, both are cleaned and brought back to their respective areas.

Racing Quarter horse mares can be artificially inseminated.

The American Quarter Horses Association does not have a “live cover” requirement for registration of quarterhorses. Artificial insemination is an acceptable method of breeding. .https://www.aqha.com/forms-and-resources

Artificial Insemination: The first thing we have to do is collect the semen from the stallion. This process begins with cleaning the stud thoroughly to keep the process sanitary.

Next, a mare in heat will be introduced to the horse, to excite him. After he is sufficiently excited, the mare will be walked near a dummy mount fitted with an artificial vagina and an attached sterile collection bag. The stallion will mount the dummy and ejaculate into the artificial vagina, and the semen is collected.

Now that we have successfully collected the semen, it can be introduced into a mare. The typical procedure is to wrap the mare’s tail and hold it out of the way. Next, the vagina and the surrounding area are cleaned.

The veterinarian then inserts a tube inside the mare which extends into the uterus. Once the tube is confirmed to be in place, the semen is injected from a syringe into the tube. Afterward, the mare is observed to ensure she is ovulating if not, medicine will be used to induce ovulation.

You may elect to confirm pregnancy with a mobile ultrasound scanner. (You can check out the products review page for information about mobile ultrasound devices)

Choosing the right stud is critical.

The first step in the breeding process is determining what stud you want to breed with your broodmare. This is the most important step in the process and also the hardest.

There is no sure fire method to determine which stud is best to breed to your mare. However, there are bloodlines that do match better than others. Also, certain studs are generally more successful than others regardless of the amount of races they’ve won in their career.

Racehorse breeding is a high-risk gamble.

bred, racehorses,
Morning workout

Racehorse breeding is a genetic lottery. All the numbers are in the pool you just have to be lucky enough to match them correctly to have a winner. What methods are used by the breeder to increase their chances of producing a winner?

Horse owners dream of owning the next Kentucky Derby or All-American futurity winner. Yes, the purse money is excellent, but the real windfall comes from stud fees.

For example, American Pharoah won the first Triple Crown in 37 years in 2015. His stud fees started at $200,000 per cover, and he could cover over 100 mares per year. (Click here to read an article about why some racehorses are gelded)

Genetics is critical in racehorse breeding.

To understand the importance of genetics in horseracing lets look at some of the winners of the Kentucky Derby. A total of twelve Kentucky Derby winners have sired Derby winners, including three triple crown winners who have gone on to sire Kentucky Derby winners.

Although Secretariat a Kentucky Derby winner himself never sired a Kentucky Derby winner, he did sire some great runners as well.

War Front currently has the highest stud fee at $250,000 per cover. Although not a Kentucky Derby winner, he descends from an excellent bloodline, he is the son of Danzig and grandson of Northern Dancer.

Northern Dancer won the 1964 Kentucky Derby and Preakness Stakes and went on to become one of the most successful sires of the 20th century. A War Front colt qualified for the 2019 Kentucky Derby.

To breed a racehorse that will be successful is challenging. You not only need to have a horse with good conformation that can withstand the rigors of training and racing he must also be fast enough to win.

Choosing which horses to mate is difficult.


Through the years humans have developed different theories on how to produce the ultimate horse. The following are some of these methods.

Telegonic is ancient theory not proven effective.

Telegonic theory has been around since the days of Aristotle, and the basic premise is that previous pregnancies influence future offspring.
The theory goes that when a stud covers a mare, his genes remain with the horse and will influence the next offspring.

As a mare has more foals, she will have a higher chance of producing offspring with the best genes from all her previous mating partners. The telegonic theory has lost favor with many breeders.

Linebreeding is the most popular breeding method.

Linebreeding is the presence of an ancestor twice or more in a horse’s pedigree with at least one strain present from each parent. There are many reasons this is desirable.

Breeders have determined that if the horses who appeared in the pedigree more than once were present through a different son or daughter, it improved the horse. This leads to a reduction in genetic variance and an increase in the desired traits.

A stallion passes his Y-chromosome to his sons and his X-chromosomes to his daughters. This could explain why line-breeding on a horse via a son and a daughter is exceptionally successful. Linebreeding is the most popular form of reproduction in thoroughbreds.

Pattern breeding is linebreeding with a twist.

Pattern Breeding is a variation of linebreeding, wherein you try to repeat a pattern of ancestors found in the broodmare with a similar family found in the stallions pedigree.

Two or three influential ancestors in the same section of lineage increase the chances of passing the desirable characteristics to the offspring. Pattern breeding is still a viable method used by breeders today.

Inbreeding is no longer a prefered breeding method.

Inbreeding is the duplication of ancestors within the first four generations. Although there has been some success with inbreeding horses over the years, it is no longer a favored breeding method.

We know the stories of hemophilia amongst the royal bloodlines of Europe. Similar issues can arise with the inbreeding of horses.

Outcrossing/outbreeding increases genetic diversity.

Outcrossing or outbreeding is breeding of unrelated horses. This is done to increase genetic diversity in the bloodline reducing the probability of genetic abnormalities.

We know line-breeding can lead to the production of a successful racehorse; however, too much inbreeding can lead to physical problems. Studies have shown that mares with too much of the same genetic makeup will benefit from the introduction of new blood.

Outcrossing provides for the introduction of new DNA by breeding with a stud completely outside her family tree. Today it is tough to find pedigrees without some cross when you look back six generations.

To “Nick” a horse means to link successful bloodlines.

To determine which bloodlines cross best with a broodmare is referred to as a Nick. Nick is the term used to describe a proven successful link between two lines of stallions.


A good example is Northern Dancer/Star Kingdom pedigrees. Broodmares from the Star Kingdom line has proven to produce successful offspring from Nothern Dancer stallions.

There are many other successful combinations. Nicks have led to the positive development of the thoroughbred horse. For years professional nickers made an excellent living advising owners on the best

Nick for their horses. However, with the advent of the internet and DNA studies, Nickers are not as prevalent.

Appendix bred can be registered as a Quarter horse.

An appendix bred horse is a cross between a registered quarter horse and a registered thoroughbred. The appendix reference may continue down the pedigree-based on certain conditions.

Appendix bred horse is desired for displaying the best traits of both breeds, calmer disposition of a quarter horse and the thoroughbred’s athletic ability.

Artificial insemination is good for horse racing.

The reasons why artificial insemination is good for the horseracing industry.

  • Allows Stallions to breed more mares
  • Safer for the horses and the handlers
  • Help to regulate the costs of breeding

Artificial insemination harms horseracing.

The reasons why artificial insemination is not good for horseracing

  • Dilutes the gene pool and creates inferior horses. Lower class mares will be bred.
  • Only the most desirable stallions will be used, and thus the gene pool size will be reduced.
  • Price and demand, artificial insemination will reduce the value of the stallion stud service through dilution of the market, this would also lead to a reduction in the value of the horses overall.
  • Many horsemen respect the old ways of doing things and do not like change.

After all the calculations and time spent researching pedigrees to determine the best match for your broodmare, there is still no guarantee. Foals are stillborn. Colts and fillies break legs.

Horses can’t run for numerous reasons or struggle to make it through training. Even successful runners sometimes fail as studs or broodmares. Breeding horses is like the lottery.

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