American Thoroughbred



Understanding Sprinting Thoroughbred Lines
in Sport Horses



Domino- the all American Sprinter



Americans, stop being ashamed of your Thoroughbred horses! This article is meant to help you understand the sprinting lines in the American Thoroughbred, so you will no longer have to worry about them, and maybe use them to your advantage in creating the perfect sport horse.And to inform the American breeder how wrong this blanket assessment of our domestic Thoroughbred is by presenting the real facts.

The American breeder has been coached into a belief that their American brand of Thoroughbred is a sprint only strain, and is a lesser type for sport horse breeding then the more stamina bred Thoroughbreds coming from other countries such as France, Australia, Germany and Ireland for examples. And our American breeders themselves, after hearing this repeatedly from sport horse 'experts' are now repeating this assessment as if it is gospel.

The fact is that France is the world leader in producing stamina strains of Thoroughbred, England is a close 2nd and here is the shocker: America is 3rd in world production of stamina racers. But it is even more dramatic than that, the rest of those other supposedly stamina producing countries hardly make a scratch in stayer production and the American Thoroughbred actually supplies more than twice the amount of stayers as all those other countries combined. I know, you don't believe me- afterall you have listened for years to criticisms of the American Thoroughbred from 'experts' at your breed societies. But let me ask you, did you ever do any research on this yourself? I know you didn't, because until I did I believed those experts myself.

Is the modern American Thoroughbred too speed oriented? Yes and no. In America (and in many other countries) racehorses have been selectively bred for the fast maturing brilliant types. There is a quicker return for the racehorse breeder, if it shows brilliance early on- at 2, then it can be sold for a profit or even be put to stud. However, many of the sprinter-bred horses do not train on well, and they lack the stamina to succeed at the classics. In order to get that early brillance, the breeders must concentrate the speed genetics which can result in too extreme a type. Plenty of American Thoroughbreds are sprinters- that is true, but what is not true is the assumption that is all America produces. The greater truth is that America 'rocks' in all the catagories of Thoroughbred- we lead the way in Classic length winners, and this is going to be a shocker- we produce 25% of the world's stayers.

Now after more research I discovered something else, the bedrock of the modern American Thoroughbred is the superior ancestors it is descended from- and these ancestors, horses like Lexington, are the greatest distance racers the world has ever seen. I am not exaggerating, the ancestors of our modern Tb were regularly running 4-mile heat races, several times in one race meet- that means they ran 4 miles, rested for a short while and then they were off on another 4 mile race- and possibly another- the winner was the best 2 out of 3 heats. If there were three or more racers in the race, and if a different horse won each of the 3 heats, then they would even have a 4th heat. That means these horses would run 8 to 16 miles at a full gallop in one race. And they ran not just as a 2 or 3 year old, but well into the double digits- the great racer Boston until he was 10- and was only retired because he was going blind- not unsound of limb or wind. Think about it and read more about the 4-mile racers of yesteryear These racers are sitting in the background of your pedigrees- no other country came close to this level of sport talent. The best news is because of Tesio methods we know how to engineer our lineages so that we build up these amazing individuals in the background.

When I first wrote this article I did not have all the information I do now, and was still in part under the 'warmblood spell', so I accepted some of the bias about the American-bred Thoroughbred, and even worried that my own classic length racemare was too close to that dread sprinter type to produce anything good. But now with many years of experience and study under my belt I am much more able to decern the falsity that abounds in our common knowledge in sport horse breeding.

Two things to consider, first the American Thoroughbred produces 25% of the world's stayer bloodlines- that is no small amount (see Thoroughbred article for more on this). Second, sprint bloodlines are perfectly acceptable breeding material for all sport pursuits- even the breeders of distance racing Tbs know that they have to add a speed horse now and then to keep the distance speed. It is the individual bloodline we have to look at, is it sound, and is it a pure sprinter or is it a multi-distance length line.

For a case in point, consider Nasrullah who is everywhere there are winning sport horses no matter the discipline. Read any article about which bloodlines are showing up in show jumpers, the eventers and sure enough you will find him. Yet Nasrullah, a 1940 Irish-bred, who with plenty of time passed for proper evaluation of his breeding legacy, he is found in the 'Brilliant' column on the chef-de-race list. Brilliant is one of the sprinter classification columns, and Nasrullah is found only in this one- so this is what his breeding legacy is- he is a sprinter sire.

Okay, so the Nasrullah factor poses a problem for the 'no sprinter' rule in warmblood breeding- the facts do not support the bias. However, now we see that like everything else we have learned- it is the bloodline that matters- if the bloodline is a good sport source- like Nasrullah, or even his sire Nearco- who by the way is classified as classic and sprint sire, then it will probably work extremely well in our breeding projects.

This is such a radical turn from the conventional wisdom that it will probably help us to get a stronger understanding about just what constitutes a sprinter bred horse, and the scientific evaluation of those horses that produce sprinters has given the Thoroughbred industry some remarkable facts.

When Clive Harper applied scientific method into the evaluation of the Thoroughbred pedigree he came up with statistics that demonstrate the power of the pedigree pattern in dominance building. Breeding Principle: The Thoroughbred pedigree researchers determined that speed can be built into a horse by duplicating 3/4 siblings close up, and that both speed and class by duplicating full siblings close up. Surprisingly the speed making duplicated individuals are often stayers, not sprinters! On the other hand, the statistics show that stamina is built by multiple duplications in the 6th through 10th generation. They also found that failure to revisit the stamina background strength closer up, that is funneling it forward in the 4th through 6th generations can cause dissipation of the talent developed in the far reaches. We will examine these principles closer in the evaluation of known sprinter sources below. More on Pedigree Generation Position

Stamina Lines in the American Thoroughbred

So, what is the story here? Let's examine the sprinting Thoroughbred and what it is made of, and I think you will be a little surprised. The great equine scholar, Alexander MacKay-Smith traced the speed influences in Thoroughbreds in his "Speed and the Thoroughbred"- an excellent work. He stated that the sprinting lines in the modern Thoroughbred all originate at 6 sources. I say a thank you to Mr. Mackay-Smith, and present them here for your understanding, they are:

St. Simon- a true wonder horse, born in 1881 in England, and some say he is the most successful sire ever. I don't think I have ever seen a modern Thoroughbred pedigree where he is not represented multiple times. He was unbeaten as a racehorse, although he wasn't raced until after he was 3. And like other great sires he had serious temperament issues which he sometimes passed on. He is pre-potent for speed, at all distances.. That means he produced fast distance horses as well as sprinters.


St. Simon




Domino - born 1891 in America, pre-eminent sprint sire, although his grandsons Celt and Colin were great classic mid-distance winners- the best of their era. (Colin beat the stayer Fair Play three times including the Belmont Stakes.) Domino is found in our modern sport horse quite often through both Black Toney and Blue Larkspur

See how often Black Toney shows up in the top show jumpers.


Americus- also born in the USA (1892), but he was shipped to Ireland where he strongly influenced the European Thoroughbred by producing Americus Girl who in turn gave us two mares who created racing and breeding dynasties in the English Thoroughbred: Mumtaz Mahal and Lady Josephine.(below)


The Tetrarch -born in 1911 in England, called the spotted wonder for obvious reasons was unbeaten at 2, and produced the sprint sire: Tetratema and the amazing Mumtaz Mahal called the fastest filly ever. Mumtaz Mahal is out of an Americus dam. The Tetrarch also produced notable stayer such as Salmon Trout, and the jury is still out on whether he is truly a sprinter himself as he won at 2- considered the best two year ever by some, but was injured twice in the front legs and retired to stud. Could he run long? No one is sure. The Tetrarch, like Domino above is found in the best sport horses of today.



Phalaris- the most predominant sire line today, was born in 1913 in England, was the fastest horse of his day at a mile. I challenge you to find a good sport horse today, in any country, without a Phalaris line in him! He produced mid-distance horses as well as sprinters. Phalaris is a source of great hind end impulsion, but can also give weak front legs. He is behind both Nearco and Nasrullah mentioned above. His ability to transmit great impulsion is seen in the Hanoverian sire Lauries Crusador.




Havresac - born in 1915, a top Italian sire, used by Tesio on his stayer mares; he is sire of Nogara. Tesio avoided sprint lines until late in his career. When he finally let some in he got his world beaters: Nearco and Ribot.





"Sprinters are built downhill". Another point we often hear is that a sprinter has low withers and a high hindquarter- 'built downhill'. The great equine scholar MacKay-Smith stated that the high hind quarter we so associate with sprinters comes down the genetic trail from the Godolphin Arabian (a Turkoman). Turkoman horses were best at races of 4 to 20 miles and they were not good sprinters.- So this is not a sprint linked trait.

Here is another: One of the greatest horses of recent times, anywhere, is Secretariat. He won at all distances, on all surfaces, with energy to spare. You certainly couldn't classify him as a sprinter, yet he contains all six of the above Sprint lines.

So, obviously there is more to this then sprint equals sprint.

What do these sprint sources' pedigrees tell us? I found there are some noticeable pedigree patterns in these horses, for instance 4 of the 6 are out of one inbred parent, with the other parent directly engaging that inbreeding. The other two are closely inbred themselves. This is just what the experts told us- that inbreeding to close relatives builds speed.

St.Simon- is by the inbred Galopin, who is 2x2 to the half siblings:Merope and Voltigeur. The dam brought in the full sister to Voltigeur: Velicipede. St. Simon is the best son of Galopin and a genetic giant in Thoroughbred breeding.

Phalaris- is out of inbred Bromus who is 1x2 to a son and daughter of Springfield. The sire Polymelus brings in a Hampton line- who is brother to Wenlock who is behind Sainfoin the Springfield son, and he adds a Bend Or line who is a genetic relative to Sunrise, the Springfield daughter. Springfield is 4x4 to the full siblings Pasinquade and Touchstone.

Havresac- his dam Hor Concours is inbred 4x2 to St. Simon and his full sister Angelica. His sire Rabelais brings in another St. Simon line, which makes Havresac 2x3x5 to St. Simon and his full sister.

Domino- His dam, Mannie Grey, is inbred through her dam Lizzie G., who is 2x3 to War Dance/Lecomte, 3/4 brothers. His sire's dam, Hira is 3/4 genetic sister to Lizzie G., which brings together Lexington-Lecomte 3x3x4x4.The Domino line is represented also by sires that are inbred to him- Ultimus and High Time. The great Quarter Horse typesetter Three Bars is also strongly bred to Domino.

The Tetrarch- creates a close inbreeding himself with Bend Or and his 3/4 sister Rose of York 3x3, plus there is an additional 1/2 sibling to each of these two, 3x3.

Americus- is 2x2 to the full siblings the Nun/Norfolk, by Lexington out of Novice, a Glencoe daughter.

In these major sources of sprint speed in the modern Tb (with the exception of Springfield) the bloodlines that are closely duplicated are in themselves not sprint lines- this is important- It is the pedigree pattern that provides the sprint or stamina factor, not the individual line that is duplicated. For instance, Lexington is an old style stayer but his close duplication creates amazing speed in Americus and Domino.

So there you have the notorious sources of sprint lines in our modern Thoroughbred. As you can see they are not just an American phenomenon, and they can easily be adjusted by proper breeding technique.

Why is this important to Sport Horse breeders? First, we can not avoid these lines, so we better find a way to use them, and second, we can apply the breeding principle in designing our own pedigrees to our advantage. The sprint lines deliver brilliance, courage and strong hearts, which we can certainly find a use for in our sport product.

Inbreeding concentrates whatever is there in the genes. We now can see that close inbreeding of fast staying lines even like Lexington -the world record holder for 4 mile racing- can cause sprinters. We can apply this knowledge not just to our Thoroughbred lines, but warn us to be careful on how we inbreed or linebreed to the other sport line carriers. It is very important that when we closely breed, that the lines we choose are sound, sane and talented. To closely breed in something that is talented, but has a weakness or some unsoundness can flaw our gene pool for generations. Remember always that the influence you concentrate and balance in your pedigree construction will be the most dominant.

Mumtaz Mahal- an example of successful close breeding

On the Pedigree Generation Page the experts told us to do our duplications in the engine room- and this is in most cases the way for us to go. For sport breeders, if you loosen up the duplications, use the engine room area and sex balance the multiples, you will get the ability, and the pre-potence, but maybe not the problems we sometimes see in closely inbred horses.

With inbreeding there is something important you need to keep in mind- inbreeding does not cause mutations or defects to occur. It only increases the odds that if there is a defect in the geneotype that it is more likely to be seen in an inbred individual. Inbreeding concentrates whatever is in the gene pool- that is why it is so powerful a tool, but also why we should use it with caution and intelligence.

However, remember that inbreeding is a tool we use to set type, and we should not be afraid to use it, but to use it carefully and intelligently. When it works it produces typesetters or improvers- those individual horses that can upgrade a breeding program in short order.

Example of a Successful Inbred Sport Horse Stallion- Noteworthy.
And Asher, a successful example of inbreeding to an Elite mare.

Back to The Importance of the Thoroughbred in Sport Horse Breeding

real stayers- see what a real stamina horse is made of