The Pembroke County Guardian and Cardigan Reporter

Agriculture. SOME PRINCIPLES OF STOCK-BREEDING. INTRODUCTORY.—The general principles governing breeding apply equally to all farm stock, from poultry upwards, and we think that a brief recapitulation of them may not be without interest to many of cur readers. THE LAW or HEREDITY.—The general hereditary principle that offspring resemble their parents within certain limits is the basis upon which amelioration by breeding depends. Though the actual limits of this impressed similarity caunot be exactly defined, it is none the less sure that all parent organisms trans- mit their general likeness wit hi a limits to their Erogeny. Thus the main characteristics of a normal orse are similar to those of its sire and dam, and of practically all other horses. THB PRINCIPLE OF VARIATION.—Every organism naturally varies in numberless minor characteristics from its parents and birtbmates, and this underly- ing, inherent tendency to variation, is transmitted like other attributes and is universal in action, so that, no two living things are exactly alike. If the law of heredity were so precise in its nature as to carry every attribute of the parents over to the offspring improvement by breeding would probably be im- possible, but the oonstant factor of variation admits of an individual being better than its parents, and so of progressive improvement, since this individual may by natural hereditary variation impress the desired qualities to a greater degree on some of its progeny. SELECTION AND SUCCESS.—Since like begets like within certain limits the breeder desiring to improve his stock mates those showing most tendency towards the desired attribute or attributes, always bearing in mind that family characteristics are more likely to be reproduced in the offspring than are the character- istics of any single individual. Possibly some of the progeny will exhibit a marked tendency to improve- ment in the required direction, and by progressive selection of the most suitable individuals, generation after generation, combined with judicious mating, the amelioration may be fixed or rendered so permanent that the breeder may reasonably rely on its hereditary transmission in the strain. There is an alluring glamour about the popular notion that by merely crossing parents of given at- tributes a desired type of animal can be produced with the greatest of ease, and it is to be feared that the novice sometimes exhausts his enthusiasm, growing in dark places for the secreta of successful breeders, the magic wand which will enable him also to co-itrol the infinite powers of nature. The practical breeder, however, knows that his chief power of improving his animals lies in selection patient, painstaking, and persistent selection. This is his only secret," and it is, too, nature's one great and fundamental principle underlying the improvement of all stock. In-breed- ing is within limits helpful, possibly essential; but in-breeding without judicious and continuous selec- tion is useless, for it is the litter which amoiiornte", fixes, and develops all strains. IN-A-ND.iN-BREr,DING.-In-breedir,g signifies the mating together of animals more or less closely re- lated. Occasionally by natural variation combined with careful selection a markedly improved animal is produced, and the observant breeder may theu resort to in-breeding to accumulate the blood of this super- ior individual in its descendants, thus greatly increas- ing the chances of th amelioration beir:g pe;p-)-,L;atl-d in the strain. The higher the ]>ercent*&e Of i-he im- proved animal's blood ooticeair&U-d iu his descendants the greater is the likelihood of the superior character- istics being hereditarily transmitted in the family it founds. For the sake of illustration se will presume X and Y are two sheep of the MUIS breed, Y being ot nor- maily good quality, and X a distinct advance in the direction of the type desired. Then the blood of the offspring of these sheep will be half that 01 X and hall Y. Now if X be in-bred to the progeny of this first mating the blood of the resulting lambs or lamb will be three-quarters X, and by repeating the process for another generation the produce would be seven- eighths X. Unfortunately nature exacts a penalty for this transgression of her laws, and in-and-in-breeding of this character, while helping to fix the desired type, too often results in deterioration of constitution, size, bone, fertility, and mental vigour. Many instances of these evils following in-breeding might be quoted, and not a few in which no appreciable variation has resulted. It is however certain that the system applied to animals is not attended with such favour- able results as with man, this fact boing probably attributable to the greater degree of selection practised in the case of stock, and to mental diseases being less prevalent in animals. By judicious selection and the rigorous weeding out of every unhealthy, defeotive, or faulty animal the injurious results of in-breeding may be to a great extent avoided: A comparatively slight physical defect or constitutional weakness, however, in one of the selected animals may be so intensified in the family by in-breeding as to become a serious danger since bad qualities are quite as likely to be multiplied as are the desired characteristics and weakness of cor stitution means the most favourable conditions for the introduction of all the diseases to which animals are liable. The selection and mating of related animals should be controlled by their vigour and suitability for one another as well as by their actual degree of consang- uinity, and the extent to which in-breeding *»" safely carried depends mainly on the sV;" ty be suitable animals are selected. T* .,u with which must be wholly disco^ U any case the system even the iilighf- "Ioued at the appearance of in -est warning symptoms of deterioration. _I.le evolution of a new type of animal in-breed- ing is useful to fix the strain from diversified material, and to so strengthen the desired characteristics that they may be prepotent over all other influences but promiscuous, indiscriminate in-breeding is most dele- terious. BREEDING FROJU THE BEST.—When the novice breeder has once firmly grasped a correct ideal of what constitutes perfection, that is when he learns not only exactly what he wants to breed but what is worth breeding, it remains only to breed from the best; but the question of what really is the best is one over which many beginners come to grief. The aphorism that like begets like," though founded on a law of organic life, is misleading, because the hereditary tendency to likeness in the progeny may manifest itself in one or two characteristics only, and these inconspicuous and possibly undesirable. Now the cumulative experience of breeders proves that the more uniformly and persistently a family presents certain characters the greater is the likelihood of members of the family transmitting these characters, and that the character of the whole family is infinitely more important from the breeder's point of view than is any unit of the family. To consider only individ- ual excellence is a fatal bar to the attainment of success. The most perfect animal of any variety may ba a sport or throw-back, and may not be able to im- part its" distinctive characteristics to its progeny. such a sport seldom brings permanent improvement, which is only insured by slow and systematic aug- mentation of desirable characteristics, and the equally graduhl elimination of objectionable features. Hence the breeder is not unduly influenced by individual excellence, but considers first the excellence of the family or strain, and then breeds from the best avail- able animal of the family which most consistently produces the type of animal nearest his ideal. WILLIAM TOOGOOD, Southampton.