THE BREEDING OF LIVE STOCK

Dominion, Volume 21, Issue 14, 11 October 1927, Page 12

THE BREEDING OF LIVE STOCK

By

J. A. C.

(Special for The Dominion.) All Rights Reserved. in. The genetics of animal breeding and the physiology problems that are presented to the investigator and tho experimenter have been described (as far as our knowledge of tlie subject will permit of description) in numerous books and papers. These writings are all lucid enough to the minds of trained scientists and to a limited number of breeders who have taken the pains to inform themselves ns to the exact meanings of tho technical or scientific terms used. To the average farmer and breeder, however, probably more than nine tenths of that literature is not understandable; at any rate its more subtle points cannot bo grasped. This fact presents a serious difficulty to the present writer, whose object is to simplify tho information available to such an extent that every dairy farmer or pig breeder may understand and benefit by the discoveries so far ascertained. The late Professor Huxley could do that without much effort; but ho had few, if any, successful imitators in that respect. Herbert Spencer, for instance, described evolution thus: "Evolution is an integration of matter and a concomitant dissipation of motion, during which the matter passes from an indefinite, incoherent nomogeniety, and during which tho retained motion undergoes a parallel transformation.” Now that definition is not only perfectly correct, but it is also quite clear to every physicist and quite a host of other people also; yet to the great majority of readers it is not even "as clear as mud’’; nor would the much-prized "shilling dictionary” afford much assistance in explaining technical terms that are constantly being added to our language. If you call an ordinary high school boy a homozygous or a heterozygous animal he might feel inclined to throw stones at vou, yet your description of him would be quite scientifically correct; but he could not grasp your meaning. Long pedigrees are valuable, but many who can boast of them may not feel flattered if they were told the strict scientific truth that each and every individual along the whole line had their origin in gametes and zygotes. In Spite of these drawbacks, evolution is as important to every stock breeder As his milk cans are to. the dairy farmer or his shearing machines to the flock owner. Darwin wrote eight volumes of books in explanation of it nearly half a century ago, and many intelligent people to-day misunderstand his meaning, and many more have misunderstood the man. He was execrated for his alleged irreligious teaching, though in one of his

books, the "Origin of Species, 0 he rebuked one of his critics by saying that such a view "would be a travesty on the works of God/" which Darwin never attempted to oppose. He was a close student and observer of Nature, which he regarded as ’‘the works of God/* and his profound investigations led to the discovery of unalterable law or system in every department, whether animal or vegetable, and that system is summarised in tho one word "Evolution.” He collected immense masses of facts upon which he constructed the profound and now generally admitted . theory that gained for him a world-wide fame; but he never allowed himself to pry into the metaphysical aspects of things, which lie regarded as going beyond the capacity of human understanding; or, in other words, he realised that the natural mind could not transcend Nature in order to grasp the ways and purposes. of the supernatural. The instincts of birds and animals lie regarded in that light, and though ho studied those instincts very closely as to their advantages in the great’struggle for existence, lie says: "I will not attempt any definition of ■ instinct. I have nothing to do with the origin of mmtal processes any more than I have with those of life itself.” Sufficient for his purpose was the fact that every living thing possesses an instinct more or less strongly developed, which enables tho pigeon to find its way back home in a direct line over strange country that it has never before, seen, or the blind . worm to find its food in. the dark recesses of the earth, that it is a hereditary faculty and an endowment of Nature, and that without it the whole species wholly or partly depending upon it for its welfare would inevitably be doomed to gradual extinction. What ie it but instinct that induces the buffalo, to refuse to mix his species with any breed of domestic eattle unless he is bred with them from infancy? Yet the buffalo and the Shorthorn belong to the 4 saine zoological family; but Nature instinctively, and, we suppose, unconsciously, too, dictates to that unreasoning beast that any such union would be at least inadvisable, and so it would be if tho resultant hybrid progeny had to live the wild life and endure the hardships imposed upon the buffalo by its environment. Should not that fact alone afford a noteworthy lesson to those' breeders who are endeavouring too hurriedly to produce useful hybrids with, organisms that possess a dominant instinct? To be successful it is more than feasible to assume that if that trait exists it must be atrophied or crushed out by a long process of inbreeding and its environment entirely altered, for there is no other way. Even where union has been established in those wide crossings Nature frequently expresses its abhorrence most plainly by refusing to endow the hybrid with the faculty of fertility, and here it must be stated that infertility in thoroughbreds is not due to any such cause, but rather must it be attributed to structural or accidental defects in one or both of the mated animals. Darwin laid stress upon ‘■he importance of environment and what ho termed “natural selection." By "environment," of course, he meant'the natural conditions under which the animals lived —their opportunity to get sufficient food end shelter, freedom from attack, etc., which, it will be readily seen, had a very potent bearing on the destiny of all species. The Urus became extinct notwithstanding his "terrible ferocity” and his ability to combat the onslaughts of all other wild animils in his environment, because he was hunted by man, not alone for his flesh, tut also because he was a danger to human life. It is with "natural selection,” however, -that we are more concerned, in dealing with the subject of breeding, and it may surprise many that this mental giant held that not only was there a process of natural selection as between males and females in their undomesticated state, emphasised by what we.have said of the buffalo, but that in every stage of growth from, the zvgote and gamete to the mature animal the process is continued.. To make this clear it may be explained that the existence of both these infinitely small specks have since Darwin’s day been undeniably proved by the biologists* and are actually seen under the microscope; and it is found that the first stage in the formation of a foetal body is commenced by the union of two cells not nearly as large as a very small pin’s head, called gametes. These are dissimilar in structure, and when they unite they become a zygote, which means a yoke. Every poultry breeder has seen the structural changes that take place in a fertile egg in the process* of hatching, and that gives an excellent illustration of what takes place within the fertilised zygote, but with this difference only, that the hatching

is done within the mother’s body instead of in the incubator, but the process is the same. Continuous change goes on within the cell until it divides into two cells, those two into four, four into eight, and so on, each attaching themselves to their allotted parts in forming the body that is eventually destined to become the mature animal, ' directed by that mysterious law which Darwin called "natural selection. It would seem as though the cell itself possesses an instinct, which we cannot define, to perform all the natural functions that are necessary to the perpetuation of life. Chemists are familiar with the affinity that certain elements have tor one another, and the repulsions exhibited by others —oil ana water, for instance; but whether this is a manifestation of what w;e call instinct we must leave the chemists to decide. Be that as it may. there is ample evidence to show that the whole of the chai acteristics possessed by the mature animal originate in the zygote, or the gamete, and are altered only by its environment. It is now held that even sex is determined by the zygote or the gamete, and Dr. Crew, ILD., Ph.D., or Edinburgh, goes so far as to say that "To a slight extent it is already possible to control the sex ratio.” “there is every reason to maintain that within the next ten years such measures will have been devised and made available to the breeder.” That prediction may or may not be fulfilled; but if it is, it is pertinent to remark that such gross interference ifvith tho established laws of Nature may not, after all, be a profitable undertaking. Certainly, from the ethical point of view, it is not desirable. Presumably the object of such an experiment would be to limit the number of male animals (the average proportion of males to females now produced is stated to be iw to 118); but while it would result in a vast increase in the totals of nocks and herds, it may (very probably would) result in a very undesirable diminution or market prices, except in countries pos- • sessing an unlimited range of area. I (To be continued.)