SCIENCE OF BREEDING.

Dominion, Volume 5, Issue 1378, 2 March 1912, Page 6

SCIENCE OF BREEDING.

TWO FUNDAMENTAL LAWS. Tho researches of science have thrown considerable light on the factors underlying breeding, success in which proves so elusive to any but those of ripe experience or possessed of natural intuition. It has been observed that amongst wild animals there is considerable similarity of type, but as soon as they are subjected to domestic conditions decided variations begin to spring up between individual members of the same breed. This is duo to the fact that the conditions of life tiro far less stable and uniform for tho former than for tho latter, and amongst wild animals tho crossing of different varieties is far less prevalent. The determination of the influences affecting tho successful mating of domestic animals is therefore one of much importance.

There are two fundamental laws which underlio breeding (says Mr. A. E. B. Fcilding in.,tho "Live Stock Journal")! Tho first is that like produces like, and the second that variation is more or less spontaneous. The first law can only be said to apply to breeds whose members have been uniform in typo for several generations; in other words, to animals of' good pedigree. Every animal has a pedigree, but it only becomes a good pedigree when it can bo shown that the animal's ancestors were possessed in a marked degree of the desired qualities of that particular breed, and his power to transmit his good qualities to his offspring will vary with tho number of his ancestors who have had these qualities. It mnst also he borne in mind that bad qualities can be accumulated in a beast just as well as good ones.

VARIATION, ATAVISM, ETC. Variation, atavism, or reversion is the tendency of animals to produce offspring which resemble so'mo former, and possibly very remote, parent, who possessed characteristics which have disappeared with the lapse of years. As stated above, such reversion is more or less spontaneous, and may be tho result of crossing, excess of food, climate, exercise, etc. A desirable point in an animal may be missing in its progeny, owing to its having been smothered by the strong prepotent powers of the other parent, but the point is not lost, it ismerely dormant, and may again appear in some future descendant, when tho latter will be said to havo reverted. As an example, oho may ijuote a polled breed of cattle in which there occasionally appears a horned animal, owing to the breed originally having had horns, and

bo members are liable to revert. By the judicious eolection and crossing of animals exhibiting variations it is desirable to fix, new types are produced.

FIXITY OP CHARACTER. It is the object of the breeder not only to produco animals that will yield what is required of them, but also to produce animals capable of producing like animals, and their power of doing this will depend on their fixity of character—that is, on their prepotent powers. The greater an animal's prepotent powers, the greater its capacity to stamp its characteristics on its offspring, to the more or less complete exclusion of tho characteristics possessed by the other parent, assuming the latter's prepotent powers to bo inferior. This is a point that must not bo overlooked in breeding, as an animal can only bo produced having the mean of its parents' characteristics providing both the male and female possess prepotency in an equal degree. When Aberdeen-Angus cattle are crossed with Shorthorns the progeny resembles tho Angus most, because it possesses greater prepotent powers. Wo have seen the effect of atavism and of prepotency on breeding; the second point to consider is the fact that every animal possesses secondary sexual characteristics—in other words, ' every malo has female characteristics, albeit in' an undeveloped form, and vice versa. • If this were not so, a cow could not transmit her milking- qualities through her sou to her grand-daughter, yet it is well known that the best way to improve a poor herd of milking cows is to cross them with a bull whose mother was a noted dairy cow, and tho improvement is due to the fact that the bull's secondary female characteristics, which lio dormant iu himself, become fully developed in his daughters. Again, a fighting cock will pass his fighting qualities through his daughter to her son. In this connection it is interesting to note that the older animals become, the more their secondary characteristics assert themsclvos. SELECTION. Atavism, prepotency and secondary characteristics may be said to be natural factors that underlie breeding, and the successful breeder has to givo due consideration to them when mating his animals if he would attain the desired end. There is, howevar, a fourth point, and one which the breeder directly controls. I refer to selection. Selection, as manipulated bv man, is quite different to natural selection, the Jattcr resolving itself into the survival of the fittest. Man only selects for tho production of characters that will benefit him, whereas Nature selects [or the benefit of the animals themselves. Grouse may be instanced as an example of natural selection; hawks destroy large numbers of grouse every year, mid tho more nearly the grouse's plumage approximates to that of the heather which surrounds it, tho less likely it is to bo seen by tho hawks, consequently, by this process of n&tursl selection the colour

of grouse tends to resemble tho colour of heather. The improvement of any breed of live stock is dependent on the skill ot breeders in electing tho best animals for, mating, and, further, .by surrounding their offspring with those conditions ot life which will favour tho retention of the good qualities attained, and encourage variation in the right direction.

SYSTEMS OF BREEDING. So much for tho main factors affecting breeding, and now let us turn to the systems of breeding which are followed. Tho first is that known as breeding m-aiul-in, and to tho adoption of. this system in the old days we owe much of the excellence of our present breeds; but at the same time the stock were coarse, rough, and strong, and tho effect of this system of breeding animals closely related to each other was lo tone I hem down and improve the quality of the breed, but this has a limit, and as soon as that limit is exceeded tho constitution and breeding powers of the animals begin to suffer. Breeding in-and-in nowadays must bo done with the greatest care, and only with stock likelv to withstand any ill effects it may produce. Tho great advantago of tho system is to produco rapid fixity 01 tvpo, and it may bo resorted to when a d'esirablo variation appears in an animal which it is advisable to fix iu the breed. It should be noted that somo variations are very stable; others, again, are very unstable, and, in spite of in-brccding, disappear at onco. The second system of breeding is that known as breeding in lino, and is really a variation of the preceding. When the great breeders of the past had toned down thci? stock by in-breeding, they then divided the stock into families, and crosses woro no closer than a sire mated with his grand-daughter. This system enables one to get much of the advantage of in-breeding with less risk of deterioration setting in. The third and best-known system is that of cross-breeding. This is tho mating of animals of quito different breeds; tho crossing of strains of one breed is not cross-breeding, but is the infusing of one strain with the blood of another. There are great possibilities in All authorities agree that a constant intermixing of the samo kind of blood produces degeneration. A chnngo of blood helps towards the improvement of animals by imparting more size, quality, and fattening power. Great extremes should always be avoided in crossing; mating animals having points in common is best. What might be namod the fourth system of breeding is that known as early maturity. By this is meant tho power of stock to assume good carcass weights early

in life, and such complete their -growth and dentition earlier than usual. The advantages attaching to the adoption of this system are that moro animals can bo kept on the farm, as tho food necessary for feeding animals from two to threo years old is saved, and there is a consequent saving of time, labour, and risk. There is always a great demand for earlyriponcd meat, and so it pays to cultivato it. Early maturity is promoted amongst animals by breeding from animals rather younger than usual, coupled with proper feeding and good management.