Sat. Dec 3rd, 2022

Animal Breeding Line Breeding

Animal Breeding Line Breeding

Animal Breeding Line Breeding has been practiced by not a few who object to in-and-in breeding in the full meaning of the term. It would be correct to say that but a few of the more noted herds and flocks have been long maintained without more or less of line breeding having been practiced in the families from which the males have been chosen.

Line Breeding Defined. —Line breeding may be defined as the process of breeding within the members of one family or of a limited number of families possessed of similar types. As usually conducted no animals are inter-bred which are not intricately connected in the general lines of their blood.

It is in a sense a continuation of in-and-in breeding, the relationships in line breeding, however, being more distant. The animals that are line bred are more commonly descended from animals that have been bred in-and-in.

For instance, from a few foundation animals closely in-and-in bred, several divergent streams may flow out. These divergent streams represent families and very probably more or less divergent types. When the streams become fully divergent, that is to say, from the time the families become distinctly separate, the males are chosen from within these families, sometimes called strains, and from that separating period line breeding may be said to begin.

But line breeding may also be the outcome of the blending of two distinct strains, each of which has probably been more or less in-bred. It differs from in-breeding in the virtual exclusion of alien blood and in continuity.

The relationships in the former are in a sense closer. When in-breeding, the blood may be promiscuous in its near origin. When line breeding, it is unmixed with extraneous blood from what may be regarded as its starting point. Line breeding may be spoken of as repeated acts of in-breeding, the relations becoming less close as the starting point is receded from, because of the increase in the number of individuals.

The Starting Point in Line Breeding. —As now understood it would not be possible in all instances to define exactly the starting point of line breeding. It may commence with a pair of animals, or with a limited number. When it does, in-and-in breeding is practiced at first. But it may also commence at a later period in the history of the breed.

More commonly it begins at that point where the outcome of in-and-in breeding diverges sufficiently to admit of the formation of distinct families descended wholly or chiefly from one ancestor. In line breeding the males are subsequently chosen from this family.

Close Breeding Defined. —Close breeding signifies the mating of closely related animals. Its relationship to in-and-in breeding has already been pointed out (see page 112). In some instances, it may mean the same thing as line breeding, but ordinarily it differs from the latter in the relationships being closer, and from in-and-in breeding in their not being so close. It differs further from line breeding in the less degree of the continuity in the breeding. As with the other terms applied to breeding it is not easily defined. It is not easy to distinguish in all instances between what should be regarded as close breeding and what as line breeding.

High Breeding Defined. —High breeding signifies a rigorous selection of breeding stock with reference to a definite standard. It is sometimes regarded as synonymous with close breeding, but it differs from close breeding and also from line breeding in allowing the selections to extend to unrelated animals. High breeding may have reference to form only or to pedigree or to both.

Where practiced, a high standard is set as to both form and pedigree, and the animals to be mated are chosen accordingly. They may be related or unrelated, that is to say, this line of breeding may be the same as in-and-in breeding or the same as line breeding, or it may be neither, nor a combination of these systems.

When it considers only animal form it is not likely to be markedly successful. Nor will it be any more successful if it simply regards pedigree without considering form. When it duly considers both form and pedigree and does not include too much of line breeding or of in-and-in breeding, and when, moreover, good judgment is shown in the selections, high breeding is but another name for wise breeding, and is worthy of all consideration. But when it is follow- ed practically on the lines of in-and-in breeding, the results will be the same.

The Objects of Line Breeding. —The chief objectives of line breeding are to obtain uniformity of type in the stud, herd, or flock, and to maintain the same.

In other words, it is an effort to obtain greater average prepotency in the animals. Similarity of type in the whole herd is at once evidence of prepotency in the parent or parents and a guaranty of the same in the offspring. Now this result is facilitated by the maintenance of identity or of similarity of blood in both sexes. This will, of course, secure and render permanent certain dominant properties.

But the same end may be obtained though not so quickly by carefully selecting males from a line bred family. This method of line breeding is considered safer than the former and many of those who practice it now do so on these lines. But eventually it becomes line breeding of the first class rather than of the second, where no fresh blood is brought into the stud, herd, or flock, through the purchase of females.

And just here it may be stated that there is a magic influence about that word uniformity when applied to animal breeding, which is apt to lead the average breeder to place too high an estimate upon it. The advantages of uniformity depend almost entirely on the character of the uniformity. There may be uniformity of a low type as well as uniformity of a high type.

In breeding, the first is not so desirable as less uniformity of a higher type. It is when the uniformity sought is of a high standard that it is to be prized.

The Evils from Successive Line Breeding. — Line breeding is usually beneficial for a time, but it should not be carried too far, as there is danger that it will intensify defects, as well as useful qualities. When it does it becomes so far, an evil. Ultimately it will produce all the evils consequent upon in-and-in breeding, though less in degree. These include loss of size, delicacy of constitution, impaired powers of re- production and gradual deterioration. As these have been discussed in Chapter X. they will not be further discussed here.

It should be noticed, however, that some of those evils may be gendered in the system before they become markedly apparent. For instance, the seeds of increasing delicacy of constitution may be sown before they are distinctly apparent, as evidenced by the results that flow from them. The results come later.

When the evils do appear to a marked degree, they have become so incorporated in the animals, so much a part of the system, that much loss results before they can be corrected by judicious out-crossing. In this tendency first to create defects and then to transmit them, lies the greatest danger from in-and-in breeding and from line breeding.

Illustrations of Excessive Line Breeding. — Il- lustrations of long continued line breeding is furnished in the various herds of wild cattle sheltered by certain parks in Great Britain during the past century.

While at the beginning of the century there were at least seven herds, now more than half the number are gone, and their total extinction in the not distant future is by no means improbable. It would seem peculiarly fortunate that illustrations of this question are furnished by herds which cover so long a period.

Some of them have been kept within the enclosed grounds of certain nobility for more than 500 years. The most famous of these herds, viz., that at Chillingham Park, has been line bred for more than seven hundred years. These wild or semi-wild cattle have been bred under circumstances the most favorable to successful line breeding that could well be imagined.

These wild or semi-wild cattle have been bred under circumstances the most favorable to successful line breeding that could well be imagined. The continuity of sameness in bloodlines has not been disturbed by out-crosses. The breeding has been from the most vigorous sires, as each in turn secured the proficiency in the herd. The exemption from the enervating influences of domestication was most complete since they were not confined.

They were also supplied with food, when necessary, in winter. And yet, from natural causes, these herds are gradually waning in numbers, insomuch that it is feared that the extinction of those that yet survive is only a question of time. These cattle are not prolific, although their surroundings are eminently favorable to prolificacy. For are they of large size. Is not the conclusion legitimate, therefore, that these results are the outcome of too long continued line breeding?

The results of the experience of the molders of the various leading types of Shorthorns point in the same direction.

The Collings Bros inbred closely as a rule,” though not at the outset, but their practice varied. It was they who introduced into their herd the Galloway blood, and the resultant fact remains that the highest priced animals at their dispersion sale were those possessed of this blood.

But too much should not be made of this fact as the percentage of Galloway blood in many of the animals possessing it was small indeed.

Darwin states that during the first thirteen years of breeding at Kirk Levington, Thomas Bates bred most closely, and during the next seventeen years of breeding he made several outcrosses, that is, to say, he introduced Shorthorn bulls from other herds. It was after he began the introduction of these outcrosses that his greatest triumphs were made in the showing.

During the earlier period of the breeding conducted by the Booths, new blood was repeatedly introduced by purchasing females, and an occasional outcross was also made by bringing males from other herds, and for a time all went well. Later the breeding was closer, with the outcome that it was found necessary to introduce fresh blood freely to preserve the high average of excellence in these cattle.

The Cruikshank cattle were much mixed in their blood lines during the first decades of the breeding conducted at Sittyton many of the females brought into the herd from without were chosen from various sources and were not specially line bred. Later the breeding was more closely in line and for the reason, among others, that by breeding thus, Mr. Cruikshank was the better able to reap the fruits which grew out of his great reputation as a breeder.

The fame which in time came to those cattle was doubtless due to the great skill shown in the selection of males to use upon females of varied breeding. But the herd was dispersed at a period too early to show what the outcome would finally have been from the closer breeding practiced. The experience of those breeders, therefore, as far as it goes, is certainly less favorable to long continued line breeding than to the more promiscuous blending of blood elements within the breed.

Line Breeding Cannot be Carried on Indefinitely. —From what has been said above it is manifest that line breeding cannot be carried on indefinitely without sowing the seeds of ultimate deterioration. The postponement of the evil day will depend upon such conditions as the skill of the breeder, the numbers of the herd or flock, the naturalness, or otherwise of the conditions of keep, and the management.

Of course, the more skillful the breeder, the greater the number of animals in the herd or flock, the more natural the conditions and the more sensible the management the less quickly will the evils from line breeding too long continued show themselves.

At least one excellent flock of line bred sheep is now in existence into which an outcross has not been introduced for about a century. The reference is to the famous flock of Border Leicester at Merton Lodge in Berwick shire, Scotland. But the fact is significant that American purchasers at the present time are looking to other flocks not thus line bred when making selections.

They assign as a reason, that while the Merton Lodge flock furnishes sires of much prepotency, they are lacking in scale.

Remedy for Evils from Breeding too Closely. — The evils consequent upon line breeding or in-and-in breeding too long continued may be remedied in part by the judicious introduction of an out-cross or a succession of out-crosses, carefully made. The timely introduction of the same may be made to ward off those evils or to prevent them entirely. That line breeding may be made to aid in furnishing prepotent sires cannot be questioned and, in this fact, lies one of the strongest arguments for practicing it.

That a time eventually comes when it ought to be discontinued even for this purpose is equally true. There is decided difficulty, however, in knowing when and where to stop, that is, just when and where to intro- duce the out-cross. As soon, however, as signs of deterioration in any direction become apparent, they should be taken as danger signals calling to the breeder to halt.

When the evils have become at all prenominated this remedy may work slowly, since the evils may have become in a sense dominant. Whether there is any way by which the benefits of line breeding in the production of sires may be secured continuously without gendering the evils complained of does not yet appear to have been demonstrated. It would be practicable to draw sires, for a time, from a line bred family, and at the same time to have another line bred family coming from which sires could be chosen later.

Such breeding would, however, encounter two difficulties, viz. : That the period covered by the breeding of the average individual is too short for such a demonstration, and the results from the males of the second line bred family would be uncertain until proved. With all the merit that line breeding possesses it must be acknowledged that it is a steed which breeders cannot always control to their satisfaction.

An Out-cross Defined. —An out-cross may be de- fined as the use of a sire of unrelated blood upon females of the same breed that have been bred in line or that are in-and-in bred, but it may also mean crossing high grade or pure-bred females with a male of another breed. It is only in the former sense that it will be discussed in the present chapter.

Unrelated blood, if healthy and vigorous, infuses fresh vigor into the stocks upon which it has been crossed. The reasons for this increase of vigor are not well understood, but it has been noticed that it is frequently greater when the animals used in making the out- cross have been brought from places wide apart, and when the conditions such as relate to climate and production are different.

Thus, it is that Shorthorn blood brought from Britain seems to have a renovating influence on herds in this country though not bred in line, aim probably the same would be true of Shorthorn blood exported from the United States to Britain. This would seem to be akin to the renovation which in many instances comes through the introduction of the seeds of plants from outside sources. But it would not be correct to say that all such changes with animals or plants bring renovation.

 Benefits from Introducing an Outcross. —The benefits which flow from increased vigor the result of an out-cross include:

  1. An increase of size and flesh-forming qualities ;
  2. An increase of milk production;
  3. Increased productivity; and
  4. Extended longevity. These benefits are virtually the opposites of the evils created by too close breeding and too long continued. They grow out of that upward, onward stimulus which increased vigor brings along with it, and which extends to every part of the system. Thus, it is that prize winning animals are so frequently found in the earlier progeny from out-crosses.

Animals Long Line Bred Produce few Specimens of Highest Excellence. —While animals long bred in line or in-and-in bred may produce an occasional specimen of high excellence, they do not produce so many of these as pure-bred animals of what may be termed mixed breeding. Such has been the record written on the page of history in the breeding of Shorthorns for the past one hundred years. No class of Shorthorn cattle has been bred line to a greater extent than certain of the Bates families. They have been in the hands of many skillful breeders, and yet the prize winners from such herds have not been relatively numerous for the past fifty years.

But, when those cattle have been judiciously crossed by Cruikshank males, the results have been of the most satisfactory character. The progeny of these out-crosses stand high in favor in the herd, in the show ring and on the block. That mixed breeding, or, as it is sometimes termed, “natural breeding,” when judiciously conducted will produce a high per- centage of excellent animals has been clearly demonstrated in the Grasmere herd already referred to (see page 109). The fact only can be stated here.

Out-crosses Should be Made Cautiously. —Outcrosses should be introduced with much care lest the variations resulting should be in a different direction from what was intended. The prepotency even of a vigorous animal cannot be measured by conjecture. When these out-crosses are made they should be made in a tentative way in about the same manner as sires are tested to judge of their prepotency. They should be mated with only a few females until the results of the outcross are apparent in the progeny. When these are quite favorable those sires should then be used freely on the herd and for as long a period as may be judicious.

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Regards, Coyalita

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