BREEDING DAIRY COWS

New Zealand Herald, Volume LXXIV, Issue 22776, 9 July 1937, Page 5

BREEDING DAIRY COWS

HEALTH AND VIGOUR

FUNDAMENTALS FOR SUCCESS WORKING WITH NATURE BV H. UREItKTON Wo must not think, because her objectives are not always our own, that Nature has 110 plan in her breeding. Her "plan" is vastly more perfect and far-sighted than our own muddled efforts, and the objectives are clear-cut and their value obvious. Our failures to achieve tho goals wo set ourselves in breeding are almost invariably the result of disobeying tho laws we sec her employing, and such success as has been won by "master breeders" has followed they - application of one or more of the major laws of evolution. We, therefore, in our "selective" breeding of livestock, cannot do better than adhere to at least the main laws of genetics which we see demonstrated on all sides among wild life. Many widely differing breeds of animals have been traced to a common parent stock, and this indicates that, from timo immemorial Naturo has boon busy evolving new types to suit new environments. When, however, the new type has proved to be sullieiently evolved to completely suit its new home, it is fixed, by a process of closo breeding, into what we call a breed —that is a uniform type with little variance in characteristics between its members. This indicates that the first objective of the breeder should bo to discover tho brood, or typo of cattle, best suited to his farm or district and then to concentrate upon securing uniformity of type in his herd. It is impossible for all the members of a mixed herd to thrive equally well in any one locality. Purity of breed produces comparative uniformity of type, but* no two individuals (unless they be twins) are exactly alike. This is a provision of Nature to provide for any variation in environment which may take place, in which those most suited will survive and so evolve a new typo or species. This variation provides the breeder with what is known as "strains." Some strains of a breed are morehealthy, more prolific or more productive than the general run of the breed, and by mating together animals having one or more of those characteristics strong!}* developed we intensify and fix these features. Nature does this by closo in-breeding. Tho members of ono family form a herd or mob and breed together so that any favourable characteristics are intensified and improve tho "strain," while any weaknesses arc similarly intensified and result in the elimination of the undesirable strains. The Origin of Prepotency This close breeding in families, or "strains," intensifies family features to such an extent that they become what wo call "prepotent." That is. they carry more than tho normal weight when the} 7 are blended with an animal which is not prepotent. Thus a cross between two animals does»not always result in a 50-50 offspring. Tho progeny is always most like the most prepotent parent in the features prominent in his strain. This prepotency is of the greatest importance in a sire, as he is the parent of many offspring each year, and hence can quickly stamp his ' presumably good features on a herd and produce uniformity of type where a mixturo previously existed.

This is the chief value of a pedigree bull. His pedigree is, or should bo, a record of constantly improving performance within one strain or family. Only then is a pedigree of value. At Variance With Nature When we come to the qualities which Nature apparently considers of greatest importance as objectives m evolution, wo find them at variance with our own ideals, 'ibis is unfortunate for us and our animals, for Nature's laws are immutable, and in I so for (is we attempt to break theru we, or our stock, suffer. Nature places the health and vigour of the animal first,, reproduction sec- ! ond and production third. If, for any ! reason the health of the animal is weakened through inheritance or wrong environment —Nature attempts to either eliminate it or prevent it from breeding. She has numerous effective methods of doing this, ranging from parasitic and disease attacks, through instinctive herd animosity to sterilitv Every observant farmer will be conversant with these "elimination tests" which Nature imposes in order that only the physically and constitutionally perfect will survive. Once healthy survival is assured, reproduction becomes the great urge and, „ ill the cow, production sufficient to adequately nourish the offspring follows as a natural sequence. Easy up to a Point Now the objective of the farmer who is building up a dairy herd is primarily to get the greatest possible production, in milk or butterfat, from the least expenditure of feed, so - he selects the strain from his chosen breed which yields the most, and mates these so as to intensify this characteristic. This is easily done, up to a point, but the limit is reached directly production weakens, or even threatens to injure the health of the animal. Then, beeauso health, or survival, is more important in Nature's scheme than 'either reproduction or production, the strain, becomes sterile, or one or other of the agencies of destruction set to work to destroy the animal. Production is definitely limited by the health and vigour of the cow, and this in turn by its ability to consume sufficient lood of the correct type to maintain all its functions. A strain of any breed which is renowned only for its steadily increasing production, and in tho * selection of which robust health has not been equally considered, is therefore not a good investment for the dairy farmer. We call robust health and vigour "constitution," and this is almost invariably indicated in conformation. Ideal Conformation is, translated into tlie simplest terms, balanced development. For "increased production to be maintained without injury to the health of tho cow, she must have proportionately developed capacity for food, air and water, and be adapted in size to the quantity and quality of feed available to her. In developing a strain within any breed, therefore, it is of the utmost importance that we select a prepotent sire having the productive inheritance that we desire, but lacking nothing in conformation which could lower his constitution. Similar, or even greater care should be exoccisdd in selecting tlie cows from which it is intended to breed herd replacements. Indeed their production record is not so important as is their health record. Because of the "sex-linkage" of some characteristics —that is the transference from one sex to the opposite of inheritance of a particular feature—a prepotent sire with high butterfat or milk production inheritance ma* 1 ''' daughters' production far above that of l dams in one generation. it is chiefly from their mothers that tho offspring inherit both their size "and conformation, and hence their constitution.