INTRICACIES OF INBREEDING

Waipa Post, Volume II, Issue 86, 16 February 1912, Page 4

INTRICACIES OF INBREEDING

ITS USES AND DANGERS. Inbreeding is without doubt responsible for a considerable amount of mischief in the breeding of stock, but as for certain purposes, it sometimes becomes a necessity, it is interesting to study how far it can be carried on without doing irreparable injury. In the bovine world, says the "Farmer and Stockbreeder," inbreeding generally produces tne worst effects on the animal's constitution and fertility so that where consanguineous mating is indiscriminately carried on for too long a period the animals so bred will suffer from infertility and general weakness. "What is, perhaps, only a slight form of weakness in the first parents may, and often does, become a fixed and severe form in succeeding generations, and what is at first no more than some transient form of weakness becomes a disease. .Thus, of course, if a certain family is exclusively bred within itself the evil becomes greater; but if bred into other families, then the evil will have a tendency to decrease. We are told in t that book that every lover of a shorthorn should read—viz., " Thomas Bates and the Kirklivington Shorthorns" —that "Lord Althorpe in his herd crosced in and in till he sacrificed constitution. His cattle had thin quarters and no breasts. Many of them were deformed and unhealthy, and he was forever doctoring and dosing them." - That shows ve'ry clearly that inbreeding carried too far and repeated one generation after another ,is dangerous to animal's health and constitution.

THE EVIL EFFECTS.

The evil effects of close breeding may to some.extent be diminished by weeding out any animals that exhibit any particular form of weakness or disease; but then the evil is not eradicated, and very soon the whole herd may be Weeded out in this way. If there is a weak spot anywhere, constant inbreeding can be relied on" to produce it or further develbpe it, and if animals.are to be produced healthy, fertile, and vigorous, inbreeding must be indulged in only with very great care and judgment. The only justification there can. possibly be for inbreeding is for the purpose of "fixing type." It is impossible to fix a type in pedigree stock without the practice of close breeding, and when that type is fixed it cannot be maintained without a certain amount of consanguineous mating. It is the on*y means of obtaining pure blood and fixity of type. No type can be regarded as fixed until several generations have shown no tendency to depart from it.

Granted that inbreeding under certain circumstances is necessary and justifiable, then the question as to how long it may be carried on without evil results to the progeny depends on the constitution and characteristics of the original parents, and the way in which the successive generations have been selected and mated. If the original parents were strong and vigorous and absolutely unrelated, and if judicious selection has been made of. the progeny for breeding purposes in subsequent generations, and only those animals bred from, both male and female, that are healthy and strong, with no signs of weakness or defects, then inbreeding may be carried on successfully for a much greater length of time than if the original stock from which the type is to be fixed is of delicate constitution or closely related, and if the progeny in successive generations has been carelessly selected and mated. Of course where cattle ;are being so closely bred) the'scope for. selection is extremely: narrow, arid, besides, the question;;pf type has to be constantly kept in.the forefront and animals that do not possess the desired characteristics are bound to be excluded. HOW TO AVOID TROUBLE.

Some of the evils of inbreeding may be avoided, and greater scope for selection given, by establishing several families of the same tribe, and breeding them all carefully to the desired model weeding out all the delicate and imperfect ones, and breeding only from those which are vigorous and true to type. These different families having been kept apart, though bred to the same type, do well for the purpose of getting fresh blood of the same kind from, time to time; but unless this can be accomplished by the man within his own herd there comes in a big difficulty, because different people have different ideals, and in all probability the very same blood in another's hands has been bred to quite a different type. The different effects of inbreeding on different herds of cattle and the methods employed are shown pretty, clearly by the results of inbreeding as practised by the admirers of the Bates and Booth types (particularly the former), and the results of inbreeding as far as it was pursued by Amos Cruickshank. Bates fixed his type by several

years of close breeding! coupled with great judgment and careful selection; but he had gone as far as-,i\e dared, and his herd was already beginning to show signs of :«tp evil effects of too many inbreeding by becoming: unfruitful and-showing signs of weakness of constitution, when he died, and yet his followers pursued the same system, but without any judgment or selection. It was all done on paper, and with disastrous results. The Bates cattle suffered physically. Cruickshank never practised inbreeding until he saw in Campion of England and his progeny the, type of animal he wanted, and he was able to breed in and in to Champion of England without in any way impairing the vigour of his herd, because the herd had always been bred for vigour and constitution, and only those animals were bred from that possessed the characteristics for. which Cruickshank cattle were and have ever since been famous—and pedigree was ignored. '

WORK FOR THE SKILFUL BREEDER.

It is only on this principle that in-breeding can be carried on without evil results for any length of time. Animals must only be mated that are possessed of the deshred type, and that are constitutionally healthy and vigorous, and when the progeny, after due care and selection, begin to show signs of weakness, then it becomes necessary to intr duce fresh blood. To do. this i i such a manner that the vigour of the animals is increased, whilst the type is in no way affected, taxes the skill of the breed .t to the uttermost. If he gets a real outcross, then in all probability his cattle will resort to what they originally were, and his model will be lost, and so he must select hisV fresh blood from other branches of the same family, or from a distinct, though similar family, but only distantly or not at all related. Inbreeding has been responsible for a great deal of harm in purebred stock, but yeti no type or model has ever fixed without it, and if judicious selection of the animals is pursued, it can be carried on to greater lengths without causing physical deterioration, but it can only be trusted in the hands of a very skilful breeder.