INTRICACIES OF INBREEDING

Dominion, Volume 5, Issue 1354, 3 February 1912, Page 8

INTRICACIES OF INBREEDING

ITS USES AND DANGERS. Inbreeding is without [10111)1 responsible for a considerable amount of mischief- iu the breeding of stock, but as for certain purposes, it sometimes becomes u necessity, it is interesting to study how far it can be carried on without doing irreparable injury. In the bovine world, says tlio "Farmer and Stockbreeder,'' inbreeding generally produces the worst eli'ects 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 u fixed and severe form in succeeding generations, and what is at Erst 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 beoomos greater; but if bred into other families, then the evil wilt have a tendency to decrease. Wo are told in that book that every lover of a Shorthorn should read—viz., "Thomas Bates and the ivirlclivingtoii Shorthorns"—that "Lord Althorp in his herd crossed in and in till he sacrificed constitution. His cattle had thin quarters and 110 breasts. Many of them were deformed and unhealthy, "and he was forever doctoring and dosing them." That shows very clearly that inbreeding carried too far and repeated one generation after another is dangerous to the animal's health and constitution.

The Evil Effects. The evil effects of close inbreeding 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 tho whole herd may be weeded out in this ivay. If there is a weak spot anywhere, constant inbreeding can .be relied on to produce it or further develop 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 purppse 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 wihout *a certain amount of consanguineous mating. It is the only 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 Jong 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 fliose animals bred from, both male and • female, that aro 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 "tho original stock from which the type is to be fixed is of delicate constitution be cjoselv related, and if the progeny in successive generations has been carelessly selected and mated. Of course, whore cattle aro being so closely bred, the scope for selection is extremely narrow, and, besides, the question of type has to be constantly kept m 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 mav bo ■avoided, and greater scope for selection given, by establishing several families of tho same tribe, and breeding them all carefully to the dpsired 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 tvpe, do well for the purpose of getting fresh blood of the samo kind from time to time; but unless this can be accomplished by the man herd there comes in a big difficulty, because different peoplo have different ideals, and in all probability the very samo 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 tho admirers of the Hates and Jlootli types (particularly tho former), and the' results of inbreeding as far as.it was pursued by Amos Cruickshank. Bates fixed his typo by several years of close breeding, 'coupled with great judgment and careful selection; but he had gone as far as he dared, and his herd was already beginning to show signs of the evil effects of too many years' inbreeding by becoming unfruitful and showing signs" of weakness of constitution, when ho 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. Tho Bates cattle suffered physically. Cruickshanlc' never practised inbreeding until he saw in Champion of England and his progeny tho type of animal he wanted, and ho was able to breed in and in to Champion of England without in any way impairing tho 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 tho Skilful Breeder. It is only on this principle that inbreeding can be carried on without evil results for any length of timo. Animals must only _be mated that are possessed of the desired typo, and that aro constitutionally healthy and vigorous, and when the progeny, after duo caro and selection, begiu to show signs of weakness, then it becomes necessary to introduce fresh blood. To do this in such a, manner that tho vigour of the animals is increased, whilst the type is in no way affected, taxes tho skill of tho breeder to tho uttermost. If he gets a real out-cross, then in all probability his cattle will resort to what, they originally were, and his model will be lost, and so he must select his fresh blood from other branches of tho 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 ]harni in purebred stock, but yet no type or model has ever been fixed without it, nud 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.