Page:The New International Encyclopædia 1st ed. v. 03.djvu/518

* BREEDS AND BREEDING. 456 BREEDS AND BREEDING. In practice the oflfspring nearly always shows a closer resemblance to one parent than to the other. This is attributed by slock-broeders to prepotency, which may be delinod as the superior influence "of one parent over the other in deter- mining the characteristics of the offspring. Like atavism, prepotency is a well-established plie- nomenon. recognized by all breeders, but about which little is known or can be prophesied in a particular ease. It is an important factor, espe- cially in the ease of the male, as he is selected for special desirable (lualities which he is ex- pected to impress upon his numerous progeny. Reference was made above to the j)art played by A-ariation in the evolution of breeds. It is also the factor which is responsible for the de- generation of improved breeds when left to them- selves. It may be defined as the tendency which domestic animals exhibit under certain condi- tions to differ or depart from the parental type, contrary to the law of lieredity. The principal causes of animal variation are climate, food, habits, and environment in general. It may be in the direction of improvement, in which case it can be taken advantage of by the breeder, or it may be in the opposite direction. Such varia- tions are usually prepotent over the nonnal characteristics, and are usually complex rather than simple, affecting more than one organ. This is in agreement with the law of correlation, according to which any peculiarity in the de- velopment of one organ or set of organs is usti- ally accompanied by a corresponding modifiea- tion or suppression of organs belonging to an- other part of the system. On account of this tendency to variation, it is only by the closest watchfulness that the excellence of many of the higlier developed breeds of animals can be main- tained. Success in breeding depends primarily on skill in selecting and managing the breeding stock. The animals selected should be as nearly perfect as possible in conformation and buifd, have the valuable i|ualities which it is desired to per- petuate developed in the higliest possible degree, and be capable of transmitting these <pialities to the offspring. Special attention should lie given to selecting the male, not because of any special known influence of sex, aside from prepotency, but because he impresses his characters upon a much larger nmnber of progeny than does the female. A further reason for this is the sup- posed influence which previous impivgnations, and especially the first, may. exert upon the fe- male. The hypothesis is that the influence of the male is not limited to his immediate offspring, but may extend through the female that he has impregnated to the offspring which she pro- duces subse(piently by coupling with another male. This influence is designated technically as telegony. A large number of instances of such an apparent influence are on record, and it is quite widely believed in by English breeders. The leading authorities in (ierniany have not accepted it, and those who have admitted the possibility of it consider that it has not been proved. Some interesting exiieriments with horses and zebras, recently reijortcd liy Prof. .J. C. Ewart, of Edinburgh, seem to support the belief In telegony, but for the present it must be regarded as open to some doubt. Selection and the coupling of animals is the practical application of the principles of breed- ing as briefly enuinerateil, and its successful accomplishment refpiires the ability to conceive or comprehend an ideal and to maintain or develop it. In the coupling of animals several systems or jjractices are recognized, depending upon the relationship of the sire and the dam, as in-and-in breeding, line breeding, cross-breed- ing, etc. In-anil-in breeding, or close breeding, is the coupling of animals nearly related. Re- garding the closeness of relationship implied in these terms, it not only apjiears that no definite rule has been estjiblished, but also that different writers use them Avitli a somewhat different shade of meaning. This probably accounts large- ly for the difference of opinion of writers regard- ing the merits of the jiraetice. In theorj' it rests upon the belief ( 1 ) that to produce the best animals the best obfjiinable stock should be selected and bred together, and this repeated with the offspring over and over again, thus maintaining the excellences of the family free from the intermi.xture of any less excellent blood, and fixing the desirable characters; and (2) that the in-and-in bred animals are iirepotent over others. The object sought is to establish desired forms or qualities with 'the greatest certitinty and in the least time. Those who object to close breeding hold that it carries with it danger of loss of constitutional vigor and fertility in the offspring, loss of size, and sometimes malfonna- tion. This danger undoubtedly depends ujion the extent t« which the practice is carried and upon the character of the animal. The more l)urely bred and uniform in type the stock be- comes, the greater docs the probable danger be- come ; while with miscellaneously bred stock the evil effects are comparatively slow in showing themselves. All the great breeders have prac- ticed close breeding to a greater or less extent, ai)parently for the purpose of retaining and fix- ing certain desirable characteristics that have been developed by modified conditions. They evidently intended to breed togeflier animals of the same qualities, regardless (jf relationship. The practice is generally conceded to be an im- portant means of improvement, when judiciously followed. C'lo.sely allied to inaudiii lirccding is line breeding, which, as applied to a distinct system, is comparatively new. Historically it is an off- shoot of in-and-in breeding. It consists in breed- ing within a few closely related stocks or fam- ilies, no animals being interbred which are not closely connected in the general lines of their blood. The practice tends to bring about uni- formity in a herd, reducing the animals to a single tyi>e; but it is claimed that carried too far, it leads to retrogression rather than im- provement, as every fault and defect becomes fi.xed, and deterioration in size and vigor are liable to result. Natural or miscellaneous breeding is held by conservative writers to be the safest course in the long run. In this the breeder does not con- fine himself to any family or strain of blood, but selects the best individual animals obtain- able, the sole object being to secure the best pos- sible offspring. It avoids any danger there may be in clo.se breeding, and the infusion of fresh foreign blood is held to increase the vigor of the