Breeding Planning: Selecting A Sire

When you drive by a farm and see a bright, playful young foal romping in a lush pasture with his dam, it's easy to forget how much work, money, and planning went into his breeding. Many people underestimate the planning that goes into a useful, profitable mating.

The first step in the process is getting the opinion of a qualified veterinarian as to whether your mare can and should be bred. You should also determine the approximate value and usefulness of the resulting foal, and the cost involved. Many horse owners fail to consider costs other than the stud fee, including care specific to the pregnant mare (such as ultrasound examinations) and the veterinarian's charges for delivering the foal. There's also routine veterinary care of the new foal, along with additional farriery costs, stable space, feed, and pasture.

Once the veterinarian says the mare is sound for breeding and you've planned your budget, you can begin selecting a stallion for your mare and agreeing to the breeding contract (see "Read the Fine Print" in the December 2001 issue of The Horse, article #3170 at Naturally, you want to pick a stallion that's strong in any areas your mare is weaker, but how do you do this systematically? You need to evaluate his conformation, performance of other offspring, pedigree, and any physical problems or unsoundness.

Choosing a Stallion

But how do you decide which stallion to use? Basic to all considerations is the stallion's conformation.

"The anatomical structures making up the horse determine its conformation, including its size," says Rowen D. Frandson, DVM, MS, retired chairman of the Department of Anatomy at Colorado State University's College of Veterinary Medicine and co-author of Anatomy and Physiology of Farm Animals. For years this book has been the most widely used undergraduate college anatomy textbook in animal science programs across America. Frandson has long been interested in the relationship between conformation and performance in horses.

Frandson says, "The conformation of the offspring is expected to be somewhere between that of the sire and the dam. Conformation is reflected in the characteristics of each breed. Conformation of the parents, whether good or bad, is likely to be transmitted to the offspring, with desirable or undesirable results. If the sire and the dam each have the anatomical characteristics (conformation) of the breed they represent, the offspring should be representative of the breed." The stallion, therefore, should be strong in those points in which the mare is relatively weak.

Breeding to a stallion that is conformationally better than the mare gives your prospective foal a better chance of improving upon the mare, of course. Avoid selecting a mediocre stallion and expecting your mare's good conformation points to overshadow his weak points. You might get lucky, but it's a much better idea to start with the best genetic material possible in the stallion since your mare is the unchanging factor.

Offspring and Pedigree

Besides his conformation, you need to know how well the stallion's get have been doing in the field in which you hope to use the foal. Notice that it is more important to know how the stallion's get have been doing in that field than how the stallion himself has done. Of course, sometimes the stallion isn't old enough to have two or three crops of offspring with performance records. Then you will have to base your decision on the records of the stallion himself and the get of his full- or half-siblings. In such cases, though, the stud fee should be lower than that of a stallion which has several crops in the field and whose get have done exceptionally well in competition.

An astute breeder will have studied the field (racing, showing, trail-riding, dressage, hunting, etc.) enough to know the names and pedigrees of the most successful (proven) stallions. This helps you identify the best bets among the bloodlines.

If the stallion's get have yet to perform, you must give extra consideration to the grandsires and granddams. Beyond that, although their names can look wonderful on the pedigree, third- and fourth-generation progenitors seldom have made much contribution to the prospective sire. An exception to this guideline might occur if a substantial amount of inbreeding is involved, which is practiced to "fix" certain desirable traits and thus greatly increase the odds that those traits also will be present in the offspring.

Unfortunately, inbreeding does the same for undesirable characteristics, which is one reason it is not practiced more. The other powerful reason for limiting its practice is the frequent loss of vigor in the offspring of lines that have been heavily inbred. To remedy this latter problem, the stallion owners or stud managers probably have outcrossed to a different line somewhere within a generation or two.

If inbreeding is a concern, it is useful to determine the inbreeding coefficient of the stallion. The level of inbreeding that's considered acceptable varies with the breed and the breeder, but most breeders will draw a line in the neighborhood of 15-16%.

 The inbreeding coefficient for Thoroughbreds, on average, is somewhere around 8%. Any individual, however, could have an entirely different inbreeding coefficient. The coefficients for other breeds usually are readily obtainable by studying the breed history, and have already been obtained by experts in many instances. In such cases you would want to know if the stallion you are considering is inbred to a higher or to a lower degree than the average of the breed. You certainly will want to know how the foal compares, and so will anyone considering buying the foal at a yearling sale or thereafter.

In evaluating siblings, half-siblings, sires, dams, grandsires, and granddams, the careful breeder will profit from at least a brief study of equine genetics. For instance, a given sire or dam will not necessarily pass the same genes to every offspring (see "Genetics Primer" in the November 1997 issue of The Horse, article #624 at, for more on genetics). Some sires, however, are known to be prepotent, meaning they seem to pass their good qualities along to their offspring no matter the mare's qualifications.

Because horses often possess some genes that are suppressed by the influence of others, full siblings can be entirely different from each other in certain traits and almost identical in others. This is due to one foal inheriting the dominant gene and the other inheriting the suppressed (recessive) gene. Unfortunately, there is no way for a breeder to know which alleles the horse will receive before breeding. Here the law of averages holds. That law says that the chances of getting the combination of genes you want is much greater if the sire's offspring and the offspring of the sire's siblings and half-siblings have the characteristics you want.

Evaluating Physical Problems

Another consideration is the number and kind of physical defects in the stallion (every stallion has at least one or two). Some of these are the result of heredity; others, probably the majority, are the result of environment (what happened to the stallion during and after birth). For instance, a crooked leg could be the result of an accident, or he could have been born with it. Keep in mind that the stallion's conformation might have been responsible for the defect.

Unsoundness in the stallion is another matter entirely. If the stallion is unsound, you have a red flag warning you to consider carefully breeding to him. Blindness in one or both eyes, for instance, might or might not be inherited.

Evaluate the circumstances under which the horse became unsound. For example, conformation likely had nothing to do with a leg injury received from stepping in a gopher hole. However, severe arthritis after a career of mild work such as pleasure riding might have its roots in poor joint conformation that you don't want your foal to have. Even if the unsoundness itself is not transmissible, the tendency to acquire it after birth might be so. "Faulty conformation may predispose to unsoundness," says Frandson, "and that may cause rejection of the animal for the purpose it was intended."

An advisor might recommend disqualifying on general grounds any stallion which is unsound for any reason. Many advisers, however, would not go quite that far, choosing instead to evaluate the unsoundness relative to the horse's designated discipline. For example, lameness that only shows up after full-speed race work might be perfectly acceptable for a Western pleasure candidate.

Nevertheless, if the stallion under consideration is unsound, you should discuss the matter with a qualified equine veterinarian before signing a breeding contract.

Need Help?

The extension horse specialist for your state or your county agricultural agent (both of whom can be located by checking the local telephone directory under "Cooperative Extension Service") can be helpful in evaluating potential sires. The careful breeder also will check the reputation of agents and stud managers before seeking their advice or deciding on a sire.

The extension horse specialist works for the public and is paid with public funds, not private ones. The law requires that he/she be available to consult with every citizen who needs help in any field in which he/she is experienced. You need not be a full-time or even a part-time farmer to ask for help.

In most cases, bloodstock agents or even top breeders with many stallions at their disposal can also help you work out sire selection issues. Genetics texts such as those listed below might also prove helpful in understanding breeding planning challenges.

Perhaps the most appropriate closing statement is one that has been floating around for decades, if not centuries: You can look at a horse and know what he/she seems to be; you can study the pedigree and know what the horse ought to be; but only the offspring can tell you what horse really is!

John Foss, MS, is a free-lance writer whose work has appeared in several equine publications. He also edited Anatomy and Physiology of Farm Animals and is a director of the American Horse Protection Association.


Chalkley, Lorraine A, DVM, MS; Cook, W.R., FRCVS, PhD, eds. Equine Genetics and Selection Procedures. Dallas: Equine Research, 1978.

Thrift, F.A. Animal Breeding. Lexington: F.A. Thrift, 1993.

About the Author

John Foss

John Foss is a free-lance writer whose work has appeared in several equine publications. He also edited Anatomy and Physiology of Farm Animals and is a director of the American Horse Protection Association.

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