Whenever two or three dog fanciers get together there is almost sure to be talk about linebreeding. The term may be used without any one of them having a real understanding of what it means. There seems to be much confusion, even in the minds of experienced dog breeders, about the actual meaning of the terms inbreeding and linebreeding and how to differentiate between them. The prime purpose of this article will therefore be to try to explain, as simply as possible, these two methods of breeding, as well as why they are used and what should be expected from them. In covering these types of breeding, the subject of outcrossing must of necessity enter the picture. We should know exactly what we mean when we talk of inbreeding, line breeding and outcrossing. Few breeders have a clear conception of just where one leaves off and the other begins.
Prior to supplying a greater definitiveness as to what is meant by the above systems of breeding, the following short explanations are given. In the broadest sense they contain the gist of the whole subject.
Linebreeding is mating animals who are closely related to the same ancestor, preferably one whose type it is desired to obtain in the resultant progeny. In other words, it is accomplished by using for parents dogs who are closely related to that ancestor, but are little, if at all, related to each other through any other ancestors. They are, in effect, bred in line to that common ancestor. When a breeder says his dog is linebred, one immediately questions, “Linebred to what?” As we shall see later, the answer to that question enables us to somewhat evaluate the wisdom of having used this type of breeding in that instance.
Inbreeding implies a much closer relationship between the mating pair than does linebreeding. Instead of involving second, third or more distant generations, it is generally understood to have to do with only four relationships—son to mother, father to daughter, brother to sister, half-brother to half-sister (both having the same sire and different dams, or the same dam and different sires). It should be remembered that when mating the progeny of two litters each having the same parents (from repeated matings, for instance), one is mating full blood brothers and sisters. That too is inbreeding.
There is no complete concurrence of opinion among breeders as to where linebreeding takes over from inbreeding, since the former is only a modification of the latter. We find that both terms are rather loosely used, that there are several intermediate relationships which are labeled inbreeding by some, linebreeding by others. It is difficult to make any incontrovertible definition of the two terms, if indeed not impossible. It would be only confusing if we took up here what some breeders consider to be inbreeding, others linebreeding, such as the mating of a dog to a half-brother or half-sister of one parent. There are several other such closely involved relationship matings upon which there are similar differences of opinion. However, in the broadest and most commonly accepted meanings of linebreeding and inbreeding, explanations have been given above.
The reader should understand that there is an area of breeding between interrelated animals which is not entirely covered by the terms “inbreeding” and “linebreeding” as defined here. For this type of breeding I have for years used the term “family breeding,” which, to the best of my knowledge, I myself originated. Since “family breeding” is simply an extension of both inbreeding and linebreeding, what I have to say about these will apply in some measure, of course, to family breeding.
Why Inbred or Linebred?
While it is important to understand that there are some differences in the selection of the mating dogs when using the systems of inbreeding and linebreeding, it is of far greater value to know why these types of breeding are so often employed; why they are used by almost all successful breeders of any variety of livestock and what the results are likely to be, both good and bad. We shall pursue that subject now.
The purpose of both linebreeding and inbreeding is to bring about breed improvement to get the best that is possible out of one’s matings and to upgrade his stock. Experience has shown that if more than mere multiplication is to be had, and any real and lasting results toward breed improvement are to be obtained, a breeder must use a system of linebreeding, which not only combines animals very similar in their characteristics but narrows the pedigree to a few closely related lines of descent. This “purifies” the pedigree rapidly and enables a breeder to control, to some degree, all characteristics. It discourages variability and reduces it to a minimum.
Advantages of Linebreeding
The results obtained by this system of breeding can more certainly be predicted than the average breeder realizes. Few indeed are the dog fanciers who do more than mate bitch to dog HOPING for results that is no scientific reason to expect. When by good fortune one or two above average offspring do appear, they have nothing behind them upon which to base an expectation that they will pass on their desirable traits. On the other hand, when such superior offspring are produced by linebreeding, and improvement is shown, it is backed up by the most powerful hereditary influence obtainable because of the simplicity and strength of the ancestry. If the SELECTION of this ancestry has been good, the “pulls” are all in the same direction. The records of all breeds show the pronounced salutary results that have come from judicious linebreeding.
Disadvantages of Linebreeding
Selection by pedigrees alone, without consideration being given to the physical traits of the mating pair, is the chief danger in this system of breeding. The writer can state in the following few words the most important counsel to those who would attempt linebreeding: Physical compensation is the foundation rock upon which all enduring worth must be built. A linebred pedigree is valuable or dangerous in exact proportion as the individuals have been selected. Linebreeding does not replace selection but, on the contrary, demands the most discriminating choosing within the line. If the breeder selects by pedigree, and without consideration to physical compensation, undoubtedly dogs with notable faults will result, and thus linebreeding will ensure failure quicker and more certainly than will any other known system of breeding. No other breeding plan has ever brought about the good results of linebreeding, and no other system will ever be so powerful in the production of consistently good animals, and this with the greatest certainty year after year. The principal requirement is not to abandon individual selection. A pedigree is a guarantee of bloodlines, a record of the blood of ancestors within which breeding operations and selection may, with confidence, be confined. The word “confined” is used advisedly for, after linebreeding has been practiced for a few generations, the end result is the development of what is in effect a pure breed — a breed within a breed, so to speak. When that has occurred, any attempt to introduce “cold” blood (that of unrelated dogs of other strains) is likely to result in the penalties of hybridization. The departure from linebreeding is a kind of “crossing” in a small degree, for when the blood of line bred animals becomes intensified they assume all the attributes of a distinct strain, which in truth they are, and they will likely behave as such for a long time.
In saying that linebred dogs tend to become like pure breeds, or strains within their breeds, and that their progeny from a union with unrelated animals are like hybrids, I do not mean that such breedings should never be made, or that the results would be like breeding into an entirely different breed of dogs. While in some strains of animals linebreeding and inbreeding have been intensified to a point where a herd or flock would be practically a breed of their own, I do not personally know of such a family in any breed of dogs today. However, there have been strains developed in some breeds to a point where their blood has become so dominant that it will not yield for several generations to any noticeable blending when outcrossed, the characteristics of the inbred or linebred parent always showing up. This is, of course, to be expected.
In the dog game those who criticize the system of linebreeding far outnumber its proponents. This is true for several reasons. There is a continual influx of beginners in breeding dogs, people who have never before mated one animal to another, or made any study of the subject. In their ignorance they believe that mating two dogs with “pedigrees,” especially if both are winners, or better yet, “Champions,” is all there is to it. Then, there are a multitude of breeders who refuse to take the time to make any study of genetics, who want only to breed dogs to sell and make money, and these have no interest in breed improvement through years of planned effort. Again, we have the many hit-or-miss breeders who hope for the good luck which sometimes strikes novices who by sheer accident come up with a real “topper” or two. In listing the opponents of closed-up breeding, one should not fail to mention owners of stud dogs, hungry for stud fees.
Fortunately there are in almost all breeds of dogs a very few fanciers intent upon consistently producing dogs superior to the average of the breed. Many of these know that the quickest and most certain way to do this is by linebreeding.
Because linebreeding is more generally practiced than is inbreeding, I have dwelt more on the former so far in this article. The difference in the degree of relationship of mating pairs, as generally accepted by breeders, was explained, however. It might be well now to go more fully into the subject of inbreeding. This is “breeding in and in” and is linebreeding carried to its limits. It possesses all the advantages and disadvantages of linebreeding to their utmost attainable degree. Breeding a daughter to her sire gives rise to offspring three-fourths of whose bloodlines are those of the sire, a practice which, if continued, would soon result in progeny with but one line of ancestry, practically eliminating the blood of the original dam. This form of breeding is practiced when it is desired to secure all that is possible of the blood of the sire.
On the other hand, when a dam is bred to her son or sons successively, it increases the blood of the dam. This form is practiced when it is the dam’s bloodlines one desires to preserve and intensify. Either system can, of course, be approximated by the use of a granddaughter or grandson.
The breeding together of brother and sister is inbreeding which preserves the bloodlines from both sire and dam in equal proportions. It is inferior to either of the others as a means of strengthening previously existing bloodlines, but it is freely employed when the combination of sire and dam (of the brother and sister) has proved exceptionally successful, virtually setting a new type. It has all the dangers of the other two types of inbreeding, and in a greater degree because we have no knowledge of what the new combination will produce, whereas in strengthening the proportion of one line of ancestry over another, whether it be that of the sire or the dam, we are dealing with previously existing bloodlines known to be harmonious.
Advantages of Inbreeding
As previously stated, it is linebreeding earned to its highest degree. When superior animals are used, it is the most powerful and sure way known of making the most of their excellence and perpetuating it. It is the method by which the highest possible percentage of the blood of an exceptional dog, or of a particularly fortunate “nick,” can be kept, fused into, and finally made to influence an entire line of descent. If continued, the outside blood disappears and the pedigree is quickly loaded to an almost unlimited extent by the blood of a single animal, or two at the most. In practice it is usually that of a sire. Inbreeding is not so much a matter of originating excellence as of holding and making the greatest use of it when it appears.
A large proportion of prepotent sires have been inbred or at least closely linebred. An inbred dog is, of course, enormously more prepotent than one who has outcross breeding. Its half of the ancestry having a great deal of identical blood is almost certain to dominate the offspring when mated to one of the opposite sex having an “open” pedigree. (An “open” pedigree is one in which there does not appear the name of any one dog more than once in perhaps several generations.) Inbreeding is therefore recognized as the most influential of all breeding plans or systems, supplying the simplest of all pedigrees—an advantage when we recognize the laws of inheritance. It is all that linebreeding is and more. When using either system it must again be cautioned that careful SELECTION must continually be made, both as to physical compensation and vigor and fertility. In conclusion on the matter of the advantages of inbreeding, I will repeat: No other method of breeding equals this for intensifying bloodlines, making the best use of exceptional individuals, and in building a strain within a breed.
Disadvantages of Inbreeding
Although the doubling up and intensifying of characteristics by this method of breeding ensures results that are more probable than possible and, if continued long enough, are a certainty, it works the same for one trait as another, both good and bad. It affects all characteristics of the animals involved. That is why, unless a breeder knows a good individual of his breed when he sees one, or possesses the right stock to start with, inbreeding can bring disaster. On the other hand, when the opposite is true, the most strikingly successful results can be obtained. Examples of success are many, but so can one name many failures amongst those who have dropped out of the “game” and whose “strains” vanished or are disappearing.
Inbreeding Not Necessarily Disastrous
Undeniably, no form of breeding has so many who decry it, most of them entirely ignorant on the subject. They claim it causes lack of vigor, size and fertility, and a multitude of such instances could certainly be listed. However, if what has been written here, and been proven by innumerable tests and examples, has any meaning at all, it is that ANY characteristic can be bred up or down, strengthened or weakened, by this method of breeding. Some of what we know about the results of inbreeding in animals comes from the scattered and irregularly reported experiences of breeders. It is difficult to be at all sure that the evidence against inbreeding came from using animals who were typical of their breed and should have been inbred upon at the outset. There is also the question of whether one hears of the usual effects of such breedings or only of the exceptionally bad ones. Anything undesirable which does appear is apt to be blamed on inbreeding, in spite of the fact that equally bad results often occur when no inbreeding has been done. There is usually no way of making comparisons, that is, with non-inbred animals kept under the same conditions, fed and reared in the same way.
Since it is universally agreed by all breeders and geneticists that ANY characteristic can be bred up or down, strengthened or weakened, by inbreeding (providing rigid selection is followed), why then this claim that it will bring about a loss of size, vigor and fertility? Are there some inherent traits, which come from close breeding, or is it merely that lack of vigor and fertility are commonly possessed characteristics and frequently show up? Many think it is the latter. There are so many examples of great vigor and fertility in inbred individuals, and of family lines, and even in whole species of plants and animals, as to obviate all fear of inevitable weaknesses from close breeding, but it doesn’t take much investigation to indicate to us that there is lurking weakness and infertility everywhere. It is particularly evident in humans and in domesticated animals. A large number of animals, and an apparently larger number of plants, are relatively weak and easily succumb to disease. In nature the strongest live and beget offspring, whereas the weaklings die. In breeding animals we are liable to select largely for show or utility type, yes, even for color, ignoring, or trusting to luck, as to vigor and fertility. Is it any wonder then that these traits have crept upon us until they often present a strong argument against inbreeding, although they also appear amongst entirely outcross bred dogs?
When we SELECT for vigor and fertility, as well as for other attributes, there will be less talk about the evils of inbreeding. In the meantime we shall hear about it mostly where vitality and fertility were low in the stock inbred upon. Because both of these are requisites — one to ensure life and the other for reproduction—they should be possessed in a high degree by the dogs one intends to inbreed upon.
Charles Darwin learned from hundreds of experimental tests with both plant and animal life that crossbreeding, or “out crossing” as we speak of it in dog breeding, often increases vigor and fertility. He also found that this was not true in all individuals, or in all species, even those most sensitive to inbreeding. His experiments showed that sometimes the opposite (weakness and infertility) occurred and he could not solve the mystery of the cause. Much of this “mystery” for which no explanation could then be offered has been largely dispelled by modern knowledge of heredity. It would necessitate writing at great length were I to describe even a few of his, and many other scientists’, experiments, as well as involve us in complicated scientific terms. This I will refrain from doing, to keep my treatise as understandable as possible to the average reader, since I am not writing for experienced dog breeders or students of genetics. For them this article is elementary, with nothing supplied that they do not already know.
To those for whom it is written, however, a summation of the total effects of inbreeding, and to a modified degree that of linebreeding, follows.
All characteristics both good and bad exist in various degrees in different dogs. One wishes in his matings to secure and retain the desirable characteristics, and it is easily demonstrable that this can best be accomplished by inbreeding and, to a lesser degree, by linebreeding. It is also easy to show that, by using the same methods of breeding, the lowest intensity of undesirable characteristics is attainable. Results are entirely dependent upon SELECTION, remembering that “Physical compensation is the foundation rock upon which all enduring worth must be built.”
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