The following treatise is the product of Dr. Rif’at Hussain, breeder of Thoroughbreds for several decades. His most acclaimed homebred was the exceptionally fast racer Shimatoree, whom he bred and raced in partnership with trainer Dick Dutrow (the elder). Dr. Hussain’s views on bloodlines and bloodstock are, therefore, of interest, and the Doc is one who always has a firm opinion on a mating.


Inbreeding and its advantages and disadvantages in racehorses may produce certain desirable characteristics such as speed, stamina, soundness, constitution, character, etc.

What one reads today in the trade journals is notable either for a lack of accurate information or an incomplete account of the practice of inbreeding. The analysis usually provides a very limited and overly simplistic view of inbreeding and what it can do for the breeder in fulfilling his aim of producing smashing racehorses.

There is, however, one fundamental fact that must be kept in mind – that inbreeding is the only tool that we can use to manipulate the genetic puzzle to obtain substantial improvement in the racing ability of the modern Thoroughbred provided it is done in a carefully planned and deliberately well thought out manner.

The Thoroughbred is intensely inbred and has been closely inbred from time to time during the last 300 years. Before the start of the Thoroughbred era in England, and before the stud records were kept in England, the local English horses were very closely inbred because of geography and transportation conditions as they prevailed at the time in the British Isles. Even more inbred were the imported oriental horses at the time (Arab and Barb), where it is quite well-known that the Arabs did, in fact, practice incestuous matings of their favorite horses quite frequently, in addition to the inbreeding resulting from their geographic isolation in the desert.

Charles Darwin points out in ref: to inbreeding and its effects:

  1. Close inbreeding causes loss of vigorfertility and loss of size, etc.
  2. The negative effects of inbreeding do not become evident immediately, but the positive effects do.
  3. The great advantage of inbreeding in order to maintain and enhance desirable characteristics is well established and thus far outweighs the deleterious effects.

Let us examine these dictums in reference to the Thoroughbred racehorse.


The question is loss of size.

In the case of the Thoroughbred, this has not occurred. This is due to the selection of the breeding stock that has gone on for the last 300 or so years. Classic winners today are bigger than those of 200 years ago. This is confirmed by the written records kept of measurements and the horse shoes that are still available in the museums in England.

The question is loss of vigor.

This has occurred only in those strains that were not vigorous to start with. In other words, if the breeding stock selected was not very vigorous and those ancestors being inbred to also were not very vigorous, then the inbred foals will not be very vigorous.

So if you were inbreeding to vigorous strains only (Nasrullah, St. Simon, Northern Dancer, etc) through breeding stock with a great deal of vigor, there will be no loss of vigor. Loss of vigor does not occur because of inbreeding in this case as vigor has become enhanced due to the inbreeding.

The question is loss of fertility

Caused by close inbreeding is not borne out by the facts. The fertility of the English mares was complained about in those times and after the importation of the oriental stallions – some improvement did occur in fertility in the short term. But this positive effect on fertility turned out to be quite transient. The fertility averages returned to what they were before the importation of oriental horses. Later on, the same was the case in regards to the Thoroughbred stallions and mares up to the modern era. The records of imported Thoroughbred stallions indicate that the number of barren mares has not been that significantly different from the stallions – (and mares) – that never left. So the supposed deleterious effects of in-breeding on fertility are simply not true when one looks and analyses the record.


Do the results of inbreeding appear sooner when they are positive? Sometimes they do and sometimes they do not. They physical and structural results of in-breeding become apparent if the foal inherits the racing ability – (functional) – of the ancestor to whom he or she is inbred. The commonly held fears of having foals with congenital abnormalities or weakness simply because of inbreeding are not true at all, provided you have selected the breeding stock (stallions and mares) carefully. If the two parents are strong and robust with good constitutions and are known to produce healthy foals, their inbred foals will also be strong and robust with great vitality. Most of those that condemn inbreeding today and blame it for everything from unsoundness to bleeding and wind infirmities are outside professors whose horsemanship is limited to breeding mice in the experimental labs. The critics of inbreeding in the Thoroughbred use the unrelated examples of inbreeding of mice, rabbits, monkeys, cattle and sheep to scare everyone. They hide behind their “pseudo-scientific status” and use the word “genetics” to legitimize their opinions.

Inbreeding has to be used just like any other breeding formula where the breeding stock – (or source animals) – must be based on very strict guidelines of conformation, pedigree, temperament, constitution, and character. The negative effects of inbreeding become evident only if inbreeding is used without care and without judicious selection of breeding stock. The key words toward success are proper selection of breeding stock.

Thirdly: the beneficial effects

The benefits of inbreeding far outweigh any possible deleterious effects. Most of the undesirable effects can be eliminated by careful selection of the breeding stock. If you wish to breed sound animals, you must have a sound mare that comes from a sound family and is by a sound broodmare sire. She then should be mated to a sound stallion who is from a sound sire line. In addition, the stallion or the mare to whom you are inbreeding to also must have been a sound animal and produced sound animals in their produce. And you can substitute speed or stamina, etc.

Let us examine a few hypothetical situations.

One can inbreed to Secretariat or to Northern Dancer today. Let us look at this from an analytical standpoint. Merely placing the name of Northern Dancer three times in a pedigree in a 3x3x4 position will not re-create the characteristics of Northern Dancer, or Secretariat in a similar situation. The written names in a pedigree are only an indication of the existing names on the page and no more.

The scientific basis for obtaining ANY BENEFIT from inbreeding is that the desired characteristics must be present in the stallion’s and mare’s germ cells (ovum and sperm), but then they must also be present in the resulting zygote which forms the new animal. Anyone involved in breeding thoroughbreds knows that there are billions of sperms in each ejaculate of the stallion, and there are at least thousands of ova in the mare’s ovaries. It is also well known that perhaps most, if not all, of these germ cells carry genetic codes for different and differing characteristics. That is why full brothers and full sisters seldom have the same qualities or similar abilities. Thus, repeating inbreeding on the same basis, for example: 2×4 to Bold Ruler, will not result in the same Thoroughbred with the same racing ability, even if repeated many times.

So inbreeding to Secretariat 2×2 on a six-generation pedigree page, you may not get any one specific desirable quality from him or might get only one characteristic. For example the chestnut color only but none of the structural characteristics such as skeletal and muscular conformation, or any of the functional qualities such as the galloping action, speed and acceleration, stamina and racing ability.

Thus inbreeding on a pedigree page means absolutely nothing more than the pedigree page unless the characteristics and qualities of the breeding stock – (stallion and broodmare) – involved in the close inbreeding are understood, evaluated and practiced with attention to each and every detail.

So how do we go about inbreeding in a productive fashion to produce the smashing super horse?

We solve this puzzle – of obtaining racing ability and conformation – by inbreeding in the Thoroughbred, using the tool available to manipulate the genetic puzzle and concentrate the desirable benefits with this much maligned and much praised practice.

FIRSTwhen you inbreed you must inbreed to influential and dominant, yes dominant, individuals who have proven themselves to be such beyond any question by the test of TIME.

This would mean that such influential horses would have shown tremendous racing ability on the racetrack and then shown the ability to reproduce those traits in their offspring. Such individuals can be stallions or mares, but they must be influential in transmission of their own specific characteristics.

In recent times, such individuals amongst stallions would be Bold Ruler, Northern Dancer, Ribot, Native Dancer, Turn-to, Raise a Native and so on. Amongst the mares, such individuals would be Cosmah, Almahmood, La Troienne, Grey Flight and so on. It is not necessary to limit yourself to these, but you may want to inbreed to St. Simon or Teddy, and you can do that by using animals who are inbred to these great Thoroughbreds. In fact, Tesio did do that when he produced RIBOT who has, I think, 16 or 17 crosses of St. Simon.

SECONDif you wish to inbreed, you must utilize individual mares and stallions who do in fact possess the functional – (racing ability, speed, stamina, etc) – qualities of the individual to whom you intend to inbreed.

For example, if you are trying to inbreed to Raise a Native, the source (stallion or mare) related to Raise a Native must possess the one quality that he is known for – speed and acceleration (function).

There is no point in inbreeding to Raise a Native through a son or daughter of his who had lacked speed because that horse obviously did not inherit this required quality of the Raise a Native sire line.

At the same time, if you are inbreeding to Raise a Native, you must keep in mind the unsoundness of bones that goes with his strain. So you should use stallions and mares who were sound themselves.

If you are inbreeding to Ribot, the source animals must possess the quality that Ribot is known for, namely soundness, stamina, and the ability to accelerate going a distance.

If you are inbreeding to Nasrullah, size, soundness, speed, and temperament must be present in the source of animals and so on.

THIRD, when you plan on inbreeding to a specific horse, it is better to do it through differing sources, such as full brothers or brothers and sisters who do themselves possess the quality of the ancestor to whom you are inbreeding.


If you wish to inbreed to Northern Dancer, it would be of great benefit to duplicate his name through different sources, such as by breeding a son of Lyphard to a daughter of Nureyev or of Nijinsky. This has the added benefit of providing differing physical characteristics, while perhaps reducing some of the less desirable qualities of the sire line. From Nijinsky, you could obtain size and substance while getting quality from Nureyev or Lyphard.

FOURTHdo not try to separate the yolk from the egg white. If you are trying to in-breed to Ribot, don’t be too upset about bad temper as that is part of the Ribot package or trademark – call it what you may.

The bad front legs of the In Reality line is a similar trademark. In Reality is inbred to War Relic, who is in bred to Rock Sand and Fairy Gold – all of whom had less than perfect front legs.

The late maturation of bone in the Raise a Native sire lines must be taken into account and accepted when inbreeding to this sire. One of the main reasons for the so-called unsoundness of this strain is that mentally and physically the young horses from this sire line mature very early, but their bones mature much later. The end result is that many 2-year-olds with a great deal of speed are allowed to self-destruct as their bones are not yet ready to withstand the stress of racing or even fast gallops or breezes.

Regarding bad temperament, inbreeding by itself cannot be blamed for the occurrence of bad temper. Many outbred horses have been well known to transmit their evil disposition in a dominant fashion, such as Hastings, Barcaldine, Tristan, Mata Hari, Nasrullah etc.

And finally inbreeding is only a plan where the odds of breeding good horses may be improved directly in proportion to the amount of detailed work that is done in regard to proper selection of breeding stock and carefully selecting the strains that you are trying to reinforce. If you wish to produce consistent results in your breeding of racehorses, the only real tool available is inbreeding.

You might inbreed to Northern Dancer through a son who has no race record and get only the skeletal and muscular structure (conformation) without the expected racing ability. But if you inbreed to Northern Dancer through Nureyev or Nijinsky, through Storm Bird or better still through Sadler’s Wells, you are much more likely to benefit from the planned concentration of the desired genetic pool.

On the other hand, if you were to inbreed to Secretariat, who is not a dominant stallion, it is less likely that you would obtain the desired result. The reason is that even though you are planning to place the name of Secretariat in a 3×3 position and expecting the characteristics of the Big Red Racing Machine, what the same in-breeding also does is to inbreed to Secretariat’s ancestors, such as Bold Ruler or Princequillo, any one of whom might act as a dominant factor and transmit qualities that you had not planned for in the resultant foal.

On the other hand, once you inbreed to a dominant animal such as Northern Dancer or Bold Ruler or Raise a Native, the chances of such an unexpected happening are less, as these stallions are known to be dominant in passing their physical traits, even when they sire foals with no inbreeding, as their sire record shows. So inbreed to dominant stallions and dominant mares and dominant female families.

This is where the advantages of inbreeding remain. Inbreed to dominant and influential animals through their offspring who have shown the preferred inherited characteristics of the dominant ancestors. Then and then only, the results will be consistent and satisfactory to the breeder.

Unfortunately, most of the inbreeding that actually takes place today is either accidental (fortuitous or inadvertent) or planned by those that do not have access to top-class stallions and mares, and they inbreed using less than first-class animals, with less than first-class results. This counter-selective sort of inbreeding is reported by students of bloodstock and analyzed by pedigree experts and writers in the press. And it is this practice of inbreeding which is blamed or credited with whatever the results are.

If one examines the record of deliberately planned inbreeding done by breeders who have the means to use first-class breeding stock and who inbreed to dominant stallions and mares, it has been a phenomenal success and is in fact responsible for the renowned success of horses like Flying Fox, Buckpasser, Turn-to, In Reality, Roberto, Seattle Slew, Herbager, Ribot, and others.

The history of Thoroughbred racehorses would be very different had these courageous breeders not had the faith and conviction and the resources to do what they did. Lord Derby, Col. Hall Walker, Federico Tesio, and Marcel Boussac are the icons of inbreeding. As a matter of fact, without deliberately planned in-breeding the racehorse as we know it today would not have existed.

For today, inbreeding to Mr. Prospector through Woodman, Conquistador Cielo, Forty Niner, and Majestic Light would provide an excellent possibility to concentrate speed, acceleration, and class while minimizing the problems of unsoundness and front leg confirmation defects.

One could inbreed to Bold Ruler through the sons of Seattle Slew and the daughters of Secretariat (AP Indy) or to Northern Dancer through the sons of Nureyev and Nijinsky with daughters of Storm Bird and Lyphard. This would make a great deal of sense if the sources (mares-stallions) used were excellent animals in terms of race record, female family etc.

Prepotency and inbreeding

Ribot, Nearco, Northern Dancer, and Raise a Native, Bold Ruler, Turn-to, and Native Dancer are dominant stallions. Inbreeding to them would tend to re-create and enhance their characteristics. The resultant foals will – if they are true genetic types – possess the desired qualities of their ancestors. And that is the aim of inbreeding.

On the other hand, inbreeding to animals who have not shown dominance (such as To Market, Secretariat, and most others) in siring superior racehorses themselves, will not re-create what they did not have, namely genetic prepotency, and thus inbreeding to them will not achieve the enhanced genetic transmission of racing ability in the resultant foals.

What may happen in some of the latter situations is that fortuitous – (inadvertent) – inbreeding to one of the ancestors will occur which might result in unexpectedly good results.

EXAMPLE: Spectacular Bid in-bred to To Market 3×3

Now the sire line of To Market is dead for all practical purposes and he is not known for being a top broodmare sire either. Therefore, he is certainly not a dominant or influential stallion. So inbreeding to To Market in Spectacular Bid’s pedigree has very little to do with his racing ability – (exceptional) – and has certainly not enhanced his siring ability in spite of the books of exceptional broodmares that he was bred to early in his years at stud.

Another example of close inbreeding is Broad Brush, inbred to Turn-to 3×3, but he is by Ack Ack, whose sire line is hanging by a thread. So even though Broad Brush is inbred, he is by a less-dominant sire. Turn-to is known to be a dominant and influential stallion, even though he is known to sire unsound stock. I believed that Broad Brush would sire runners of exceptional ability though they might tend to be unsound. They proved both more talented and more sound than the odds could have predicted.

And last, you have to believe that inbreeding does work and is responsible for the great racehorses of yesteryear and also is the only tool left for breeders to pursue and re-create excellence. You must think about incorporating it into your breeding plans. All the rest is superfluous. To concentrate an improved genetic pool must be pursued with care and diligence in selecting proper breeding stock. Regardless of the physical attributes, what matters in a Thoroughbred racehorse is his genetic make-up, and nothing else matters.

If Tesio had asked the statisticians before planning his matings, there would be no Nearco nor Ribot.

If Col. Hal Walker had measured his horses with tapes and rulers, the result would have been far from Blandford, Princequillo, and Bahram (bred from Hall Walker lines).

And if Lord Derby’s team had consisted of critics of inbreeding, inbreeding to Pilgrimage would never have been practiced, and thus no Swynford, no Blandford, no Blenheim, no Nasrullah, no Bold Ruler, no Secretariat, and so on.


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