IN-AND-IN BREEDING

Waikato Times, Volume XXX, Issue 176, 24 June 1873, Page 2

IN-AND-IN BREEDING

(From the Agricultural Gazette ) The subject of "in and -in brooding "is full of interest to the breeder of domestic animals Strong opinions have been expressed both m favour of and against the system, and we flunk the^e opinions linvo hcnn too generally stilted, nnd too dogmatically held. Piobabl}, in the long run, any race of amn.ii.l3 sutlers from a prolonged continuance ot clo^e breeding, and there is no doubt that all animals are impro\ed by occasional crossing, by which term we mean the infusion from time to time of fresh blood. It is, however, equally true that the early improvers of live stock — as, for example, Bakcwell, Colling, and Bates —all bred their animals very closely; and, still further, we see that the same system has been pursued by their followers down to the present day — s'lall we say without injury ? Whether or not is a difficult question, but probably while some tribes have suffered from such close breeding, others havo not, nnd the high, prices given for individual animals may be used a3 a not altogether satisfactory argument in favour of the system. Many good flocks of sheep, among which wo may mention the Leicesters of the Messrs Brown, the Foscote flock, associated with the name of Mr Barford, awl in France the Naz Hock, which for 60 years was bred without the introduction of a single strange ram ; these and many other ca«es which it is needless to cite might be used 111 illustration of the power possessed by sheep of withstanding the effects cf close interbreeding. Close breeding has the following advantages: — It ensures a uniformity of tjpe and geneial family likeness throughout a herd or flock ; it increases the disposition to lay on flesh and fat; the "quality" of the animals is improved : the transmission of the desired tj pc to offspring is rendered more certain. The disadvantages arc a diminution of vigor in constitution, a diminution in size, a diminution of fertility, an increased disposition towards those diseases to which the particular family is prone, and the appearance of new ailments directly caused by close breeding. The natural gregauoua habits of cattle and sheep may have, from long usage, insured them against tho effects of m-breeding, and this may account for the undoubted fact that they may for long be extremely closely bred without apparent injury. With shorthorns this is especially tho case, and this particular family of cattle is the one most generally brought forward in support of the system. Wo have, howeter, much evidence to show that even among cattle in-and-in breeding can only be carried on within certain limits. Thus Mr Taylor, of Grlenleigh, who3o experience as a breeder of Di.\ on cattle we gave some mouth's since, speaks decidedly against in-and-in breeding as the direst cause of disease. Youatt says that Bakewell's longhorns, a tribe which were long closely interbred, " had acquired a delicacy of constitution inconsistent w ith common management," and " the propagation of the species was not always certain." The fertility of the "wild cattle" of Cliilhngham-park > according to a letter from Mr Hardy, (1861) to Mr Darwin, is about 1 : 5 per annum. The rate of increase of the Duke of Hamilton's wild eatlle in Lanarkshire can hardly be more than 1 : 6, while on the other hand, the increase among the wild cattle of South America is estimated by Azora as from 1 :3 to 1:4. Hence we may conclude that long interbreeding has diminished the fertility of the British wild cattle, while their sizo from this and other causes must have greatly diminished since the time when their gigantic progenitor, 803 primigenius, roamed aver these islands. Azara (quoted by Mr Darwin) informs us that the inhabitants of Paraguay believe that the occasional introduction of animals from distant localities is necessary to prevent "degeneration in sue and diminution of fertility" among the herds which graze freely aver their unenclosed country. We suspect, that, were the facts forthcoming, it might be shown that even shorthorns are not entirely inured against the baneful effrets of close in-breeding No one can search the Herd Book for records of tho births of " Duchess" calves without being struck by their mfrequency ; aird the extreme prices given for this particular and excellent strain must be partially accounted for by their rarity, while their rarity is, wo suspect, due to diminishing fertility. Mr Wright, an acknowledged judge and mau of experience, asserted (vol ii, Koyal Agricultural Society's journal) that moro calves are born cripples from shorthorns than from other and less closely interbred races of cattle. A gentleman, well known to the writer, who resided in the neighborhood of the brothers Colling, informed him that when he congratulated Mrs Charles Colling on her husband's great success as a breeder of shorthorns, she replied " All ! but if you only knew of our losses ! " and proceeded to relate the difficulty they had experienced in bunging up calves, and to bewail the number they had lost. In apposition to the effects of close interbreeding may bo placed the good effects of crossing. Judicious crossing seems to expand the form and confer additional beauty on the offspring. The offspring ia in every respect a superior animal to either parent, but we must not forget that his good qualities are not completely transmissable to his progeny. Hence, although for milking and fatting purposes crossed cattle excel pure-bred ones, they cannot successfully be employed for breeding purposes. The breeder of pure shorthorns is well aware of this fact, and he will not sacrifice the latent good qualities of his stock by crossing them with inferior blood, lie knows the immediate effect would bo improvement, but he fears that tbo succeeding generations may be proportionately degraded. It will, then, be seen that the higher in excellence the stock, the more difficalt is it to advantageously cross them. A breeder of medium, or even good shorthorns, may find it easy to both cross and improve his cattle by the purchase of a bull from a somewhat superior herd. When, however, we come to the case of our tip-top herds, it is much more difficult to effect a cross with advantage. Where can Colonel Gunter or Mr Booth find cuttle out of their own herds good enough to cross their best animals with ? They are not to be found. Hence, in such cases, probably in-and-in breeding will be carried on as long as pos-ible, and such herds, instead of being crossed, will serve to cross others. It would be exceedingly rash of any one to judge of the whole question of in-breeding from a single class of facts relating to. any one species or one tribe of animals. The effect of close breeding upon shorthorns cannot be any guide to the breeding of swme, or even of other races of cattle. The subject is a wide one, and we have only very generally touched upon it in its relations to cattle and sheep. Although these two species may be for long subjected to this system, we shall find it far otherwise with pigs, dogs, rabbits, poultry, and pigeons ; and still further, there aro many interesting facts bearing upon this subject in its relations to plants as well as aniiuala.