LINE BREEDING & IN-BREEDING

Otago Witness, Issue 3396, 16 April 1919, Page 11

LINE BREEDING & IN-BREEDING

It is well that we should at the outset carefully define what we mean by the term " line-breedmg" as opposed to "in-breed-ing" (says C. M. in the Farmers' Gazette); the former is breeding from the same biood or within the same family, by selection (but not from such close affinities as parent and offspring and brother and sister),, whilst the latter is the jll-oonsidered mating of the close relations within the oue family. Even these definitions are not quite satisfactory, for the point where line : breeding ceases and in-breeding begins is difficult to determine—in fact, the way in which that point can bo determined is uncertain, the only factor available _ in such an inquiry being the result obtained. Notwithstanding this difficulty, it is beginning to be recognised that the grading up of flocks can be successfully accomplished only by line-breeding, and the large number of breeders who have refused to adopt this method have, in general, over-estimated the dangers of such a system and failed to grasp the immense benefit to be derived from its adoption. Rams are constantly being introduced into the flock in the belief that the introduction of now blood will add to its strength and vigour; yet there is evidence that some of the most valuable flocks belong to men who have never been prominent as buyers of rams. One might go further and say that there are flocks—and flocks of the highest class—which have received no introduction of new blood for the last 60 years. Even among the more modern flocks violent out-crosses are avoided by those sheepmen whose studs have passed through the initial stages and reached any degree of uniformity. In-breedinr in itself should not, it may be argued, affect the constitutions of the animals if it be not carried too far, and there should be no reason why one fault should be given prominence over another. Bat the difficulty is to determine how far in-breeding may be carried on without goiri"- too far. What in-breeding actually rloe-a" is to enlarge all the characteristics of the animals bred and to aivo prominence, to the merits and faults of the particular familv used, whether those merits or faults are those of constitution or anythin2 else, but its.results ore so uncertain that thi3 system is to be avoided; for selection is impossible owing to the small numbfrf of unit« in the family available f or selection--that is to say, circumstances prevent the culling of individuals with undesirable cyualities stamped upon them, and thus such brooding cannot do anything but deteriorate the flock. 1.-ine-breedir.g, on the othfr hand, Is so remote and complex, owing to the great number of units in a flock, that selection can be made so as to counteract the growth of particular faults and to encour-

age desirable qualities. Independently of the si iection difficulty, however, it may be staled that breeding between two descendants of a near common ancestor is intensified -in-breeding; it is in-breeding carried, to its furthest limit; whereas in-breeding between descendants of a remote common ancestor is modified in-breeding, or, as it is called to-day, line-breeding. It is remote, v and, therefore, the characterising effects of the system axe less prominent. Selection is the essential, for it is by this means that the advantage is to be reaped. No first-class flock ever existed that was not of a type, and the type cannot be fixed by any other method than selection. Yet mere selection in a flock into which fresh blood from strange families is introduced) from year to year cannot bo expected to fix any type. Of course, it must be borne in mind that while external faults are visible to the eye, and may thus be directly guarded against by selection, thero a» other characteristics, such as a weakly con* stitution or a tendency to unthriltiness> which are not so obvious, though these. too, will be eradicated by judicious annual classing. It is not my intention in any way # to disparage the usefulness of an introduction of new blood in certain cases; there are cases in which such an introduction might be necessary to correct undesirable characteristics or failings, or to give prominence to some desirable quality, out—and this is an important. thing to remember—the improvement must bo made by using a ram of the same breed and the same family as the flock it is desired to improve. At the same time the proper method for the established breeder is to reflect fearlessly all undesirable sheep. In the same way as drastic treatment is necessary when pruning a tree, so thorough classing is good for/tho flock. Let no unworthy animal bo spared. The mere moral effect of haying, a few poor animals in tho flock is bad, for it constantly lowers the standard of the breeder's excellence. Weed out the flock, then, every year on this account, but even more because a bad. tree will inevitably yield evil fruit. Above all things, a farmer should learn to shun the delicate, unthrifty, and weak in constitution. No animal, how. ever fine in appearance, if of feeble constitution, can be" expected to breed well, least of all can prepotency be looked for m a sheep of delicate health. The theory that "the methods my father and grandfather followed are good enough for me" is one of the worst ever formulated. It generally indicates that the inherited method is a foolish and careless one. Traditions of this sort are usually kept by those whose fences are rotten, whose- weeds are uncut, whose sheep are half-starved and diseased. If it were otherwise the son and .grandson would have been educated by it up to a progressive spirit, for he who is first is by his very priority of effort inspired to maintain hia-pre-eminence. What is necessary for us all is to learn what- the scientist has to teaoh, and then to apply it in a. practical, commonsense way.