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Your Horse:
Selection Of The Horse
Conformation Of Horses
Disposition Of Horses
Saddlery And Equipment For Horses
Care Of Saddlery And Leather
Feeds And Bedding For Horses
Horse Stables
Horse Pastures
The Veterinarian
Care Of Horse Feet And Shoeing
In Or Out Of The Stable
Transporting Horses
Basic Physiology Of Horses
Genetic Considerations Of Horses

Genetic Considerations Of Horses

( Originally Published 1954 )



Like many other stories about George Bernard Shaw this one is probably entirely without any basis of fact; but it does, nevertheless, illustrate some of the pitfalls that enter into our consideration of genetics, the scientific term applied to the study of inheritance. According to the legend the late famous dancer Isadora Duncan wrote to Shaw and suggested that they have a child. "With my body and your mind he should really be super being." To which Shaw replied, "But suppose he has my body and your mind!"

Some people regard heredity as a cocktail and think that mixing things in the right proportion will uniformly bring about the desired result, just as one can vary the proportions of vermouth and gin. Joe Doakes has an old mare so he decides to raise a colt. Although she has served him well he has no ideas of what kind of stock preceded her. She has a short neck, stubby pasterns and a plain head, but "she is a weight carrier" and has a wonderful disposition. So Joe promptly selects a mate and settles upon a nearby broken down bush league racer. His legs gave way because they were pipestems; he is herring-gutted and has a vile disposition, but that doesn't worry our friend, for hasn't the mare good points in these particulars? In due time the colt is foaled and raised only to have his dam's neck and pasterns and his sire's legs and temper. Or perhaps it is the other way around and the foal combines the good points. Then Joe is sure he knows all the answers and goes out and deliberately buys more mares of the same type and waits another four years to assemble his assorted mistakes.

Upgrading a large group, by means of crossing selected sires with poor or mediocre dams, can be accomplished, but only as an average of a large herd and over many generations. Some years ago I had the opportunity to study a remarkable illustration of this fact. An old college friend invited me o spend several weeks at his ranch in New Mexico. At the time they were running approximately seven thousand head of grade Herefords. Some years earlier a severe drouth had practically wiped out the stock, and for a new start they went to Old Mexico and bought practically any kind of cows they could find. To mate with these they obtained registered bulls from Kansas and each year more and better sires of pure breed were added. When I arrived it was possible to see everything from the old Mexican cows to the youngest calves which were three-quarters to seven-eighths pure stock. The quality went up just like stair steps until at the top the resemblance to pure stock was nearly complete. Along the line there were many individual failures, but they still could be sold for beef and the improvement program continued.

Unfortunately such a method is impossible for the man who hopes to raise a few horses. The time to raise a generation or two before results can be determined is too long, and there is little or no market for the failures. Before a man starts to raise horses he had best study the basic principles of heredity and select his genotypes carefully. Genotype is a fancy word which is used to denote the sum total of the characteristics that an animal is capable of transmitting to posterity. This may be unlike the phenotype which is the word used to describe the conformation and characteristics of the animal itself. Obviously, in an animal not used for breeding the latter-is the only thing of importance. The genotype of a gelding is of no moment—it isn't going anywhere. Time and thought devoted to a study of the parents and grandparents of a mare will help more in the evaluation of her breeding possibilities than will any-thing else.

Among those not grounded in genetics some really fantastic ideas have arisen. They believe in prenatal influences and think that a pinto foal is the result of having a pinto near the mare at breeding time rather than the more accurate fact that an unknown mating took place. There is the classic lawsuit about the woman who was frightened by a runaway milk wagon and when her child was born a few months later it tossed its head and made a neighing noise. It took a learned judge to clear the good name of Elmer the Borden horse.

Still others believe in the inheritance of acquired characteristics. That one was put to rest a long time ago by Weismann, a scientist who, with Teutonic thoroughness, chopped the tails off a hundred generations of rats, only to find the next ones as long as ever. A horse does not run well or jump well because his sire or dam were highly trained, but rather because they inherited the talent and in turn passed it on to be developed by the next generation. The Saddlebred carries his tail high because of the knife, a brace, and a stimulant. All of this must be repeated with each generation. The Arab carries his tail high because it is so fixed in the genes of his ancestors for thousands of years.

The science of genetics was given its foundation by Gregor Mendel, an Austrian monk who lived in the middle of the last century. By the breeding of peas he showed that the height, color, and other characteristics depend upon the presence of determining factors (genes) which behave as units, and that the second and later generations of cross breeds exhibit these characters in all possible combinations, each combination in a definite proportion of individuals.

Later researches have proved that these genes or units are grouped in larger bodies known as chromosomes, a large number of which are present in both the male and female cells. Before the male and female chromosomes unite, each splits in two and the offspring is formed by union of one of the two possible halves of the male and female chromosomes.

Perhaps an ever-simplified example in the Standardbred horse will illustrate. This strain carries both the tendency to pace and to trot. Either characteristic may be dominant in the genotype of an individual animal. If "T" represents a dominant trotter and "t" a recessive, while "P" is a dominant pacer and "p" a recessive pacer, we might mate the trotter Tt to a mare who paced but carried the heredity of Pt. The colt might be a Pt, PT, Tt or tt. If the off-spring Pt were mated to a pure trotter again, the result might be either a trotter or a pacer, but in the case of the colt tt a mating; with another pure trotter could give only TT or tt, and then the genotype would be fixed or homozygous for trotting. This, very roughly, is the method used to fix any desired characteristic in a strain. A chromosome capable of transmitting only one of a possible pair of alter-natives is accomplished by a weeding-out or line-breeding method. Whenever we make an outcross the cells take on a combination of the different strains and again become mixed or heterozygous, and for some generations it is a guess and a gamble as to the genotype of the new combination.

Centuries of selective breeding have so fixed the type of the Arab genes that there is little guesswork when two pure Arabs are mated. When an Arab is mated to an unknown mare, the marked homozygosity of the sire tends to swing the type in that direction. But when we breed an unknown mare to a newly established breed such as the Palomino, which as yet is fixed for color only, and not that in its entirety, anything can happen—and usually does.

The number of chromosomes in the horse has been figured at thirty and the genes are far more numerous. Over a hundred genes are known in barley, over two hundred have been located in man, and the much studied fruit fly has been shown to have over five hundred! The possible combinations make the variations in bridge hands seem as nothing by comparison, and explain why full brothers usually are not the same, either as phenotypes or as genotypes. For further information in this fascinating and complicated subject you are referred to ANIMAL BREEDING PLANS by Jay L. Lush of Iowa State College. I personally get badly lost in the good professor's mathematics, but his general principles are a tremendous help and I have drawn freely from his writings.

Before we go any further we might as well stop and admit that heredity is not the only thing that governs the development of an animal. Climate, nutrition, minerals, pastures, altitude, exercise and diseases all play a part in the forming and the damaging of a growing thing. But first we must have the proper genes. It is only thus that we may fix a breed type. There are several methods used by breeders to fix a type. For some reason the word inbreeding sounds bad to the layman, but actually it means mating animals more closely related than the average of the species. It has been carried on extensively and successfully in horses, cattle, and all domestic animals. Linebreeding is a form of inbreeding directed toward keeping the offspring closely related to a highly admired ancestor. Outbreeding means the mating of individuals less related than the average. It may lead to individual excellence but low breeding worth. Prepotency is the ability of an animal to make its offspring resemble that parent and each other more closely than is usual. The genetic basis for prepotency is the degree of homozygosity of the animal and whether its genes are prevailingly dominant or recessive.

Because of the nature of inheritance, even a pedigree does not tell the whole story of the genes in a given individual.

It is a lot of fun to look at a seven-generation pedigree and recall the names of famous horses in the line; but there is no way of telling just what each of these great ones handed on to our present generation. In the purebred animal the emphasis should be placed in the excellence of the two or three preceding generations. The same is true of the unregistered animal, but it is unfortunately more difficult to assemble any helpful information.

So much for the theory, but where do we go from here?

The raising of horses is a long and expensive business and much grief can be spared by care and study before the program is started. A veterinarian friend of mine once re-marked, "A good horseman is a man who never makes the same mistake once," and that is doubly true in breeding plans.

Let us suppose that we are going to start with a mare of unknown pedigree. If she herself does not possess the con-formation and disposition of a good saddle horse we had best call a halt. If the foal should turn out to resemble the dam would we be satisfied? After we have considered the mare as a phenotype and have approved her, the next step is to learn what we can about her as a genotype. If we learn that she is out of a reasonably good mare and sired by a stallion of any registered saddle type, we have something to go upon, and if we can go even one generation further on the female side we have most of the essential information. If, for example, we learn that our mare is by a Remount Service Thoroughbred stallion out of a half-Arab mare with a local reputation as a good stock horse, that puts us another notch ahead in the ladder of heredity. But if we find that our mare is just a lucky outcome of the mating of a coarse mare and an unknown range sire, perhaps we had best dismiss her from our plans and find a more suitable place for her old age, such as serving as a children's pet or a producer of light work horses at a farm establishment.

There should be no trouble in finding a good stallion, for many of them are available. The horse should be a registered animal of one of the long established saddle breeds. He may be Thoroughbred, Saddlebred, Standardbred, or Arab, the choice to depend upon the qualities desired in the foal. The Tennessee Walking Horse is another well-fixed type and can be used to advantage if there is a desire for the type of gaits for which he is noted. It is wise to eliminate stallions whose registry is based solely on the color of its mane and tail, a multicolored coat, or an amplitude of roan spots upon its rump. This does not mean that there are not good individuals of these so-called breeds, but they are not, at present, pure in their transmission of the many other genes which go to make a first class saddle horse. Also beware of the white-coated and pink-nosed fellow whose owner insists that he is an Arab. The honorary and self-appointed Arabs floating around the country could make a book all by themselves, but it is certain that, whatever else they are, they are not pure Arab and serve only to cast a reflection upon one of our oldest and finest breeds.

Finally there is a decision, and then all we can do is give the mare the best of feed and care, spend the winter evenings in dreaming, and hope.

For those fortunate persons who own Thoroughbred mares the problem is a little different and perhaps even more difficult. The breeder of unregistered horses is usually content with a sound and sensible animal of good con-formation. The breeder of pure Thoroughbreds has his sights aimed considerably higher. He studies, dreams, and slaves to raise the horse which will win the big races on the flat, or over timber, or even perhaps in the show rings. It is not often that his dreams will be completely fulfilled, but he will strive for years with that in his mind.

The late John E. Madden, one of the greatest breeders of all time, wrote as follows: "As to the so-called intricate science of breeding in so blending the blood of the sire and the dam that winners may be produced in numbers, although of absorbing interest to the student and theorist, the practical man need confine himself to the formula only of breeding a good mare to a great horse taking into due consideration the varying qualities of each, and putting his trust in like producing like, or the likeness of some good ancestor. He will have his share of winners, his good years and bad years, and the experts will tack figures on to the pedigrees of his winners, and tell him how it all happened."

One of the most popular of these systems of breeding is the Figure System of Bruce Lowe, an Australian. Probably no scheme in the long history of animal breeding compares with it. Lowe classified the winners of the three classic events in England (Derby, Oaks, and St. Leger) into Matriarchies or families upon the basis of the tap-root female ancestor to which each animal traced. Each family was as-signed a number upon the basis of its relative standing as a classic winner. Lowe designated 43 families; Allison a few years later added seven more. Many others have since been added under such names as American, Canadian, Irish, etc. Certain families such as 1, 2, 3, 4, and 5 were identified as running families and certain others as sire-producing families. The preposterous assumption of maternal predominance was at the very heart of the system. Pedigrees of successful horses were cited as guides to the proper ways to combine and blend the family numbers. Many still believe in this so-called science, which could more properly be labeled the number racket. In the English book, BEST HORSES of 1945, by Phil Bull, there is a compilation of the Lowe family numbers of about four hundred of the selling platers which ran last in their respective races. The Number One family provided 43 of these worthless nags and Family 43 supplied but one. So much for Mr. Lowe and Mr. Allison, except to add that their pseudo-science is harmless compared to the hell they have raised by their part in the Jersey Act.

Another less popular screwball system was proposed by the Frenchman Vuillier in 1927 and was called the Dosage System. Its main feature was to take the pedigrees of great horses and calculate the percentage of blood of each of its famous ancestors and breed future winners by the simple process of duplicating these percentages.

A third popular system is that of "nicks," a theory which claims that certain crosses produce more and better winners than equally good animals mated in other ways. One of the more famous ones is that of Fair Play sires with Rock Sand mares. Of course good horses came from these matings; but so did poor ones which are less easily remembered. Before long some bright light will probably start spouting off about the wonders of the cross of Heliopolis with Bull Dog mares. But before we accept this it is well to recall a few additional facts. Heliopolis is a great horse, the son of a famous sire. He has produced top colts from an assortment of good mares. Bull Dog was a good race horse and stands today at or near the top as a sire of winners and dams of winners. His mares were one of the finest collections in the world. In addition Bull Dog is the son of the immortal Teddy and the full brother of Sir Galahad III and of Quatre Bras II. Any stallion which would fail to produce good horses from mares of this direct lineage should rightly be classed as a failure. There is no harm in trying nicks if other factors are not ignored. The best nick would be to mate a leading sire with a mare of proven producing worth.

Only a few scientific studies have been made to determine the actual value of a pedigree. One of the most comprehensive of these was done by Dr. Dewey G. Steele of the University of Kentucky. Thoroughbred stakes winners of 1935-1940, and arbitrarily chosen horses that failed to make a good record during the same years. The "poors" were the horses who finished last in their races, exclusive of accident and breakdown, using a predetermined sampling system of races held on cetain days through the season. All of these pedigrees were broken down into the percentage of blood of each of the famous male lines such as Domino, St. Simon, Bend Or, Isonomy, Galopin, Hampton, Hermit, Eclipse, Herod and Matchem. It was amazing to see how little was the variation between the pedigree percentages of the winners and the "poors." Dr. Steele remarks, "Minor differences between the superior and the poor horses were hardly consistent enough nor great enough to be of practical significance." Incidentally a similar study of American Saddle Horses showed the same thing in regard to the pedigrees of the top winners and those of average or poor quality.

Now that we have dismissed all these common ideas on how winners may be bred, can we find any real guide for our plans? I think that the answer is yes. J. A. Estes has gathered considerable data to prove the contention that high racing class in the immediate ancestors is the best index of probable excellence. For example, the Futurity has been run 56 times, and 22 of its winners, or 39 percent, were the sores and daughters of stakes winning mares. Since there are so few mares of this caliber, the normal expectancy would be nearer 10 percent. A similar study by Robertson of the classic winners in England, showed convincingly that racing class of a dam is indicative of her potential value in the stud. Estes adds, "It is, more specifically, my intention to contend that it costs ten times as much to buy a pedigree without racing class as racing class without a good pedigree, and that these odds are upside down. Class without pedigree is actually a far better risk than pedigree without class. Class with pedigree (if the pedigree is limited to two generations) is of course better than either."

There are many ideas as to the relative importance of the sire and the dam. Genetically they are equally important in their contribution to the offspring, but since the mare develops, nurses and to a certain extent guides the early life of the foal, a good mother actually may have more than her genetic share in the final outcome.

Since but a very small percentage of all males foaled will ever become sires, we automatically rule out over ninety percent of the poorer ones. A good stallion is one which has the desired physical characteristics and has demonstrated his actual class by performance. If his sire and dam were also of top class, his future is doubly assured. The final proof of his value is that known as the progeny test, which means an evaluation of the quality of his get. If a horse produces good foals from poor mares, and top winners from average mares or better, we can be sure that he is one to seek. If a stallion is unraced, or too young to have progeny of racing age, he may still turn out to be a great success, but there is no way to be sure of his true value.

In choosing a mare the same considerations hold, but they become more important, because the great majority of all mares will end up at the breeding farms. It doesn't make much sense to demand the best stallion in the state and then be satisfied with any mare which has "papers" and a couple of crosses of St. Simon or Ben Brush. Consider precocity, staying power, soundness, sprinting ability, and disposition, all in the light of what you particularly wish to produce. Avoid lines which have a high transmissibility of unsoundness. The particular line is of much less moment than the excellence of the individual. Recently new importations to America have been very successful, but there is hardly a top horse which does not have more or less of the blood of the three old native lines, Domino, Ben Brush, and Fair Play. For example, the four leading American money winners, Whirlaway, Seabiscuit, First Fiddle and Sun Beau each contain one or more of the immortal three.

We cannot ever predict results with certainty; hence the fascination of horse breeding. In the BLOOD HORSE it was remarked that "heredity is not a rifle, it is a shot gun!" This is undoubtedly true, but we had still best take aim before we fire.



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