Indiscriminate out-crossing can ruin a strain. Externally the out-cross birds introduced may appear to be capable of effecting the improvements desired, but all the owner gets for his pains is a crop of unexpected faults not previously occurring extensively amongst his own birds, and not necessarily observable in the birds of the out-cross or in their parents. The seller of the out-cross is not to blame; neither is the purchaser. It is just a case of two unrelated families being unblendable.
I am, of course, taking an extreme case. It by no means infrequently occurs that quite unrelated specimens do blend and winning youngsters are produced in the first generation. But here again luck has much to do with the matter for one can never be perfectly confident of the first results when a complete out-cross is brought in. Nevertheless, I am not one of those who dogmatically asserts that it should never be necessary to introduce an unrelated bird into a good in-bred family. But in view of the risk attendant on the mating of unrelated stock the wise breeder looks for some method of modifying the dangers of out-crossing when out-crossing of some kind has become completely unavoidable if progress is to be maintained or improvements effected. I will describe two systems which have proved most effective. Their employment is not really true out-crossing; it can be better described as semi-out-crossing.
The Two-Line System
The first plan is to have two (some have more than two) inbred strains in the same colour or group of colours in the one establishment. The birds of one line are distantly related to the birds of the other line. When an out-cross is required in Family A it is taken from Family B, or vice versa. Such matings are only made when absolutely necessary, and any youngsters which the owner retains from this semi-outcross are carefully transferred to Family A or Family B, not being used first in one line and then in the other. This assists in keeping the two families so apart that they do not become one family only, which is the danger when the 2 or 3 family system is in operation.
The second semi-out-crossing system is to buy birds from another owner who has been breeding skilfully with stock originating from the same source as one's own strain, and therefore related to it. It is, of course not by any means always possible to do this. When it is practicable, however it often has most desirable effects. The fact that the birds have been kept in a different part of the country, or for some other reason not easy to ascertain, seems to make these relatives capable of bringing into another establishment a new vigour - equivalent to what is known as hybrid vigour, usually associated only with the complete out-cross. And these new birds brought in from a distance sometimes give better results than do birds bred within the establishment.
Usually when an out-cross is introduced its purpose is to improve certain properties in which a particular family is lacking. The object is to absorb the good points of the out-cross without simultaneously absorbing any undesirable features. Very occasionally the process is reversed, and the owner's own family is blended to the out-cross. I will explain this more clearly by de imaginary case. A fancier, Mr. A. owns a collection of Budgerigars which are all mostly in-bred. He is not satisfied with their general quality. They are alike in type, but winners are not forthcoming with any regularity. The owner has not had sufficiently good material with which to work. When he has brought the best out of his stock by careful selection, elimination and in-breeding to a large or small extent, that best has just not been good enough. Now a competitor of his, Mr. B. is beating him at the shows. Mr. B. is persuaded to sell one or at the most two, of his better quality specimens to Mr. A. Mr. A cannot get more of Mr. B's strain in order to breed himself more of this successful family. What can he do? He can make the best of his own and mate them to birds he has purchased from Mr. B. The first generation youngsters will be mated back to Mr. A.'s birds. In the second year, birds with more of Mr. B's blood in them than Mr. A's blood will be mated together. And so it will go on until the pedigrees contain a lot of Mr. B's strain and little or none of Mr. A's. The birds purchased originally from Mr. B will have been used as the foundation of a new family.
NO STRAINS OF THEIR OWN
Those fanciers who will never mate relations and who say they are entirely opposed to in-breeding, unless they have a very large Budgerigar establishment, cannot possibly avoid regularly buying a number of birds in order to prevent consanguinity, and those who have to depend on making extensive purchases annually obviously have to rely as much upon the ability of the breeder or breeders from whom they buy as they have upon their own capability. This seems to me to be contrary to what should be the ambition of every owner. To build up a strain of his own capable of producing the majority of his winners and stock birds. I have already indicated that I am not opposed to making purchases to bring into a stud that in which it is lacking if there are any signs of decline in one's own in-bred strain; but I consider that if a breeder has continually to being in new blood in an attempt to maintain his position, he is not only putting himself to what should be unnecessary expense but he is running a grave risk of despoiling that which he should already have accomplished by his own efforts. The risk he runs is that of introducing birds the latent characteristics of which are an unknown quantity. Scores of examples could be brought forward of achievements with all kinds of exhibition birds to bear testimony to these contentions. And I can assert that our own Budgerigars would not have gained much success if there had not been any in-breeding in our aviaries.
THE CRITICS ANSWERED
Now I will deal with the objections to in-breeding which are at times expressed. I contend that in-breeding is often blamed unjustifiably when it is not the in-breeding that is at fault but the manner in which it is applied. I have admitted that in-breeding is a two-edged sword. Just as in-breeding can bring high success so can it be the cause of dismal failure, and it is the failures which have given rise to those objections with which I am now about to deal. A stock criticism is that in-breeding is contrary to nature. This is absolutely wrong. There is undoubtedly a tremendous amount of in-breeding amongst gregarious wild birds. This is uncontrolled in-breeding.
The birds mate as their fancy dictates and not as a fancier decides. I have indicated that uncontrolled in-breeding can lead to disaster. Therefore why does it not do so well in wild life? The answer is because of that world-old rule, the survival of the fittest. The health and vigour of wild birds and animals are maintained because of the ruthless elimination of the unfit, which cannot survive climatic conditions and destruction by enemies. This is like unto the law of the jungle and it assures the maintenance of the vigour of the race. On the other hand, the fancier keeping livestock in domesticity protects them from all those handicaps with which wild creatures have to contend and he has himself to enforce that ruthless elimination of the undesirable which is so essential to ultimate success. Another criticism levelled against in-breeding is that it reduces vigour. I have already agreed that it will do so if it is allowed to but I think I have shown you how this can be avoided. Numerous examples could I bring to show that skilful in-breeding can increase vigour, just as I could bring evidence to prove that the indiscriminate mating of related stock can reduce vigour; and contrary to the contention of many people, the same remarks apply to size.
LINE-BREEDINC OF JERSEY CATTLE
A striking example of how health and stamina have not only been maintained but actually improved by the continuous mating of related animals is provided by Jersey cattle. In Jersey it has been illegal since 1862 for cattle of any kind to be allowed on to the island except for immediate slaughter. Consequently there must have been continuous line or in-line breeding, and yet the quality and health of the Jersey cattle has improved and the milk yield and the butter-fat content of the milk has increased. There has, however, been the strictest control by the Royal Jersey Agricultural Society of all breeding operations, and no cow or bull can be used for breeding purposes until it has passed a test for both appearance and pedigree conducted by the Society's inspectors.
It will thus be understood that there obtains in Jersey that strict elimination and selection which has been emphasised in the course of this must be carried out if in-breeding is to achieve its object and not be in any way harmful. And then we have those people who tell us that in-breeding is unscientific. To contradict this I will quote at length from some of our leading students of biology:- The late Chritian Wreidt wrote of the virtues of in-breeding in his book Heredity in Live-stock. He proved that in-breeding consolidates the good properties by producing birds in greater numbers homozygous for such good properties. A specimen which is homozygous for a property has the factor for it in double dose. Wreidt wrote:- "The Mendelian law teaches us . . that in-breeding results automatically in homozygous constitution. Experiments show that in-breeding in itself is not detrimental, but the genetic factors of the animal used in in-breeding alone determine whether the results are good or bad."
Wreidt demonstrated conclusively what has already been stated that when faults and constitutional weaknesses appear by in-breeding, that is actually a point in favour of this practice it has brought to the surface weakness which are latent and which without in-breeding should not be able so quickly to eliminate. According to Wreidt, by skilful in-breeding we decrease the number of birds heterozygous for bad properties and increase the number of homozygous for desired properties. Wriedt asserted that the genotype (the genetical constitution) of an animal or bird can be even more important than its actual shape and colouring. Specimens which consistently produce good offspring (the foundation birds which I have referred above) even with different mates and which stamp their excellence upon their descendants are (vide Wreidt) homozygous dominants and such birds are produced by in-breeding and continued in-breeding the number of homozygous offspring is also increased. Other quotations from Wreidt which support my arguments are the following:
"There is no sire of any breed so prepotent as an in-bred sire." "By in-breeding it is possible to determine whether a breed contains general defects which will have ... bad consequences. If a breed has remained sound and strong through several generations of in-breeding there is every reason to believe that there are no defects hidden in that breed . . ." "By careful in-breeding and careful selection through four to five generations a breed will be found which is constant for those factors selected as a basis, and at the same time free from hidden defects." "The basis on which breeding must rest is the homozygosity to be obtained by intensive in-breeding in conjunction with strict selection." And here is a quotation from the late Mr E.C. Richardson, who has a scientific correspondent to Fur and Feather:- "The lending authority is The Effects of In-breeding and Cross Breeding on Guinea Pigs, by Sewell Wright, published by the United States dept. Of Agriculture in two small volumes. "Wreidt's experiments involved the breeding of about 30,000 pigs, and the description of them, together with his commentaries, brings out clearly why in-breeding, accompanied by rigorous selection, should be the general rule, whilst an occasional out-cross may be desirable. "Very briefly, in-breeding, unaccompanied by selection, brings to the surface all characters good and bad. Hence in-breeding, plus selection, tends to preserve the good qualities. Owing, however, to the fact that mutations sometimes occur in stock, and to the fact that mutations tend as a rule, to be harmful, there may be a tendency to deteriorate with which selection inside an in-bred stock is not powerful enough to combat and in such cases an out-cross may be desirable."
Eugene Davenport in "The principles of Breeding" wrote:- "By 'line-breeding' is meant the restriction of selection and mating to the individuals of a single line of descent. The purpose of this system of breeding is real breed improvement --- to get the best that can be got out of the race, and better than ever before if possible. " Experience has shown that if the purpose be breed improvements carried to its limits, it is not enough to confine selection to the limits of the breed. All breeds are exceedingly variable, and real results aiming at anything more than mere multiplication can follow only closely drawn lines within the breed--breeding in line, or line-breeding. "Line-breeding excludes everything outside the approved and chosen line of breeding. It not only combines animals very similar in their characters, but it narrows the pedigree to few and closely related lines of descent. This purifies the pedigree rapidly and gives the ancestry the largest possible opportunity. The system is eminently conservative. It discourages variability, and rapidly reduces it to a minimum. Moreover, whatever variations do occur will be in line with the prominent characters of the chosen branch of the breed. "The nature of results secured by this system (line-breeding) can almost certainly be predicted, and when they do appear, and improvement is at hand, it is backed up by the most powerful hereditary influence obtainable, because of the simplicity and strength of the ancestry, which, if the selection has been good, all 'pulls' in the same direction. The records of all breeds will show the pronounced results that have followed judicious line-breeding.
A volume could be filled with pictures of famous animals so produced... "No other system of breeding has ever secured the results that line-breeding has secured, and if the present state of knowledge is reasonably sound, no other system will ever be so powerful in getting the most possible out of a given breed or variety, and this with the greatest certainty as we go along. * Davenport -- The Principles of Breeding: Thremmatology (Ginn and Company). The only requirement is not to abandon individual selection. A pedigree is not a crutch on which incompetence can lean, it is a guaranty of blood lines -- a field inside of which breeding operations and selection may with confidence be confined. "The word 'confined' is used advisedly, for, after line-breeding has been practised for a few generations, the ancestry become a kind of pure breed of its own -- a breed within a breed, so to speak -- and any attempt to introduce blood from other lines is likely to be followed by the pains and penalties hybridisation, for a departure from line-breeding is a kind of crossing in a small degree, and so rapidly do blood lines become intensified that line bred animals assume all the attributes of distinct strains, as they in truth are, and they will be likely to behave as such ever after.
"In saying that line-bred animals tend to behave like pure strains, and that their progeny from union with other strains behave like hybrids, it is not meant that such unions should never be made, or that such behaviour is as persistent as with real crosses. In truth, many lines are so stubborn as never to blend with others afterward (behaving like the most strongly established races), but on the other hand, most of them will yield to well- directed and persistent effort, that is to say, a line-bred herd can be modified, and in time made to assume the characters of another family, but the process is attended with a struggle and not a few failures. It has been fashionable at times to decry line-breeding, but the fact remains that a few generations of good breeding soon bring the herd and its career to a point where line-breeding must be practised or a worse alternative must be accepted, for with well-selected strains all out-breeding is mixed breeding . . .
A Close Relation
"Line-breeding carried to its limits involves the breeding together of individuals closely related. When it involves the breeding together of sire and offspring or of dam and offspring or of brother and sister, it becomes in-breeding, or 'breeding in and in'. It is line-breeding carried to its limits, and of course possesses all the advantages and disadvantages of that form of breeding carried to their utmost attainable degree. "Three forms of in-breeding are possible amongst animals, namely
"1. Breeding the sire upon his daughter, giving rise to offspring three-fourths of whose blood lines are those of the sire -- a practice which, if followed up, soon results in offspring with but one line of ancestry, thus practically eliminating the blood of the dam. This form of breeding is practised when it is desired to secure all that is possible of the blood of the sire.
"2. Breeding the dam to her son or sons successively, thus increasing the blood lines of the female side. This form is practised when it is the dam's blood lines that are to be preserved and condensed. Both systems are necessarily limited to the lifetime of the individuals involved. Either system can of course be approximated by the use of granddaughters or grandson, which would by common consent be called in-breeding, but relationship more remote would generally be regarded merely as line-breeding.
"3. Breeding together of brother and sister - a from of in-breeding which preserves the blood lines from both sire and dam in equal proportions. It is inferior to either of the others as a means of strengthening previously existing blood lines, but it is freely employed when the combination has proved exceptionally successful, virtually establishing a new type. It has all the dangers of the other two, and in a larger degree, because we have practically no acquaintance with the new combination, whereas in strengthening the proportion of one line of ancestry over another, whether it be that of the sire or that of the dam, we are dealing with previously existing blood lines known to be harmonious. . . .
"Nobody claims advantage of in-breeding per se, but it is the acme of line-breeding, and when superior individuals are at hand it is the most powerful method of making the most of their excellence. It is the method by which the highest possible percentage of the blood of an exceptional individual or of a particularly fortunate 'nick' can be preserved, fused into and ultimately made to characterise an entire line of descent on both sides. "If persisted in, the outside blood disappears by the same law that governs grading, and the pedigree is speedily enriched to an almost unlimited extent by the blood of a single animal. ... A large proportion of the really great sires have been strongly in-bred.
Only Worthwhile System
"An in-bred animal is of course enormously prepotent over everything else. Its half of the ancestry, being largely of identical blood, is almost certain to dominate the offspring. In-breeding is, therefore, recognised as the strongest of all breeding, giving rise to the simplest of pedigree - an advantage quickly recognised when we recall the law of ancestral heredity. In this respect it is all that line-breeding is and more. ... All things considered, no other known method of breeding equals this for intensifying blood lines, doubling up existing combinations, and making the most of exceptional individuals or of unusually valuable strains. ... Plenty of examples of successes can be instanced, and every breeder is familiar with them...." Davenport then went on to show the dangers of in-breeding if it were not accompanied by strict selection and ruthless elimination. In 'The Basis of Breeding' Leon F. Whitney, when referring to in-breeding says: -
"In-breeding is the great means at the disposal of the breeder to originate new breeds or purify old.... "In the past any breeder might shudder to think of mating brother to sister once. But if we select for excellent traits and discard the weaklings, I see no reason why we cannot secure strains which are not only pure for the traits in question, but which will suffer no harm from in-breeding.... "Dr. Charles B. Davenport has in-bred mice for fifty and more generations. After less than half of this number had been produced he might almost have said that every mouse was the twin of every other, so identical were they. The reason is that they inherit the same assortment of genes in uniform pairs, and there are no longer genes left which produce defective characteristics.
No Harmful Effects
"The great role of in-breeding should be the elimination of undesirable traits and the doubling-up of desirable ones. If young from in-breeding are so weak that (they cannot survive, they show beyond a doubt that within the germ plasm of the parents there are genes which, when combined actually kill the offspring. Therefore, is it not highly desirable to rid the breed of them? "I prefer to think of in-breeding as an eliminative process rather than as a strengthening process.... "In-breeding is a real art, one which demands a high degree of courage. Not every man wants to face the facts. Altogether too many people would prefer to have an animal which appears to be a splendid individual on the surface, but which is likely to pass on undesirable traits, than to have one which may not be so good to look at, but will never pass on germ plasm which will create another less desirable specimen than itself.
"An in-bred individual which is also a good type of animal itself is the truly great sire or dam, and the prize winner which is untested is not to be compared with him or her in genuine value to the breed. So here again we see that the truly great breeder is not the man who goes about buying show specimens, but rather the man who in-breeds and tests and tries his animals until he knows how to combine this with the germ plasm of others to produce the desired ideal type."
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