Submitted by admin on April 22, 2009 - 22:46
Management and Husbandry of Beef Cattle
The large beef-breeding herds are run under extensive conditions of farming such as the hill country of the North Island and the back country of the South Island. Many smaller breeding herds are kept on intensively managed farms, although these usually undertake cattle fattening as they can more easily provide better nutritional conditions than those often obtaining on the stations and runs. Hence there is a stratification in space and time; cattle are born on the hills and those not required for breeding are moved to farms on the lowlands at weaning time or at one, two, three, or more years of age, depending on policy and circumstances. Breeding cows, culled for age, may also spend a period on the flats raising calves before being slaughtered at eight years or older; in some cases they may be retained for calf raising till the age of 17 or so, but generally their peak of fertility and milk production is passed by about eight years of age.
In practice, beef heifers are mated when about 26 months of age, but if well grown they can be mated as yearlings without pregnancy and lactation adversely affecting their subsequent growth and development, provided they are fed adequately until they reach maturity at about four years of age. Some poorly grown heifers may not be mated until they are three years of age, but this will obviously reduce their lifetime performance.
Puberty is attained by well-grown heifers at the age of eight to 10 months. The normal interval between oestrus (that is, heat periods when the female will accept the services of a bull) is 20 days, and these cycles continue throughout the year or until pregnancy intervenes. Ovulation occurs 14 or more hours after oestrus has terminated, and the duration of pregnancy is approximately 282 days. Oestrous cycles may not resume until 60 or more days have elapsed since parturition. Cows can therefore be mated to calve at yearly intervals, and this is the aim of efficient management of a breeding herd.
Few if any herds achieve a 100 per cent calf-crop; that is, 100 calves born and earmarked from 100 cows mated. The calf-crop percentage for the national herd is not known but a figure of 75 is probably close to the actual percentage. Permanent infertility of cows is uncommon. Increasing numbers of cattlemen are having their breeding cows pregnancy tested in the autumn, and those not in calf are removed from the herd. This practice should lead to increased calving percentages in subsequent years as those females with poor fertility are culled.
The birth of twin beef calves is rare with an incidence of less than 0.5 per cent of all births. When the twin pair is male and female, 90 per cent of the heifers will be sterile and show male features. This is the “freemartin” condition caused by the hormones of the bull calf dominating those of the heifer calf when they were developing together in the uterus of their dam. This phenomenon is of significance only in the case of cattle twins.
Of all twins born, 60 to 8.5 per cent of them in cattle are likely to be identical; that is, they developed from a single fertilised egg, but in early embryonic life the egg divided and two separate but genetically identical calves developed. All other twins have developed from two fertilised eggs; these are referred to as fraternal twins.
Calves are weaned in the late autumn when they are six to eight months old and the cows, if fed adequately, then regain the weight lost during lactation. They should not, however, become fat as this may cause difficulties during parturition. Calves can safely be weaned at four months and, provided they then receive good feed, they develop as well as those weaned at the customary age.
A beef cow nursing its calf produces about 1,500 lb of milk or 46 lb of butterfat during a lactation of eight to nine months. The level of milk production differs among cows, but 1,000 lb of milk above or below the average of 1,500 lb would encompass most of the variation.
A calf's daily milk consumption may amount to 10 to 15 per cent of its body weight, and it will grow at a rate of 1.0 to 2.0 lb per day and attain a weaning weight of up to about 450 lb at eight months. The birth weight of a calf is about 65 lb, with bull calves weighing up to 10 lb heavier than heifer calves. The age of the dam affects the birth weight of its calf, so that heifers have lighter calves than mature cows. Aberdeen Angus cows give birth to calves which are lighter than those of Hereford or Shorthorn cows.
Yearling bulls can be mated to a small number of cows but the usual practice is to use a bull first when it is two years old. At that age he can be depastured with 30 to 35 cows for a mating season lasting three months. The vigour and fertility of a beef bull remains unimpaired until the age of six or seven when its activity tends to decline owing to increased body weight and stiffness in its movements.
Calves are earmarked when they are several weeks old with the registered mark of the property, and bull calves will be castrated at this time. Calves may be hide branded at any age, using either a hot iron or a chemical. The earmark and the hide brand provide evidence of ownership of the stock.
Weaned calves are carried on the best available pasture or on crop during their first winter. Hay or grass silage may also be fed to them during winter and early spring.
Internal parasites, when present in significant numbers, can be controlled by drenching, and body lice which often become numerous in the winter months and adversely affect the well-being of cattle, can be eliminated by spraying with an appropriate chemical at correctly spaced intervals.
The disease incidence in beef-cattle herds is usually very low in New Zealand due, no doubt, to their management on the free-range principle. The so-called metabolic diseases–bloat, grass staggers, and milk fever–take their toll and are difficult to control under the conditions prevailing on many farms. Soil deficiencies of copper, cobalt, selenium, or iodine do cause wastage of cattle in areas where one or other deficiency occurs, but control procedures are well known and readily applied by most stockmen. Diseases like tuberculosis and blackleg (a lethal anaerobic infection controllable by vaccination) are fortunately rare among beef cattle. Probably the most common diseases are lumpy jaw, caused by a fungal infection of the jaw, and wooden tongue, resulting from a bacterial infection of the tongue. Both these conditions are amenable to early treatment. The three main diseases of reproduction in cows–contagious abortion (Brucella abortus), trichomoniasis, and vibrionic abortion–can have serious effects on calving percentages and accordingly they ought to be controlled through calf–hood vaccination of heifers against contagious abortion and by strict adherence to approved breeding procedures in the case of the other two diseases.
Steers comprise the majority of cattle fattened for slaughter. They are slaughtered when about two and a half years old after having been fattened for six months or thereabouts on lowland pastures. The trend is toward slaughtering at a younger age (18 to 20 months) to obtain a lighter carcass with less wasteful fat and more tender meat. To supply this requirement, steers are brought on to fattening pastures at weaning and they may also receive a ration of hay and silage. Alternatively, they may be fed on a crop such as chou moellier and swede turnips for part of the winter. The policy at any event is to feed them well during the winter and early spring and then finish them on pasture by the late summer or autumn.
Aged bullocks are disappearing from the market as their carcasses are too heavy and fatty, and their meat is too tough to satisfy the demands of the modern consumer.
Some heifers are fattened for slaughter and are bought for the local market. They carry more fat than steers of a comparable age and weight and this makes them unpopular in the meat trade. Cows culled for age, reproductive failure, or other reasons may also be fattened, but generally they are slaughtered in an unfinished or store condition, their carcasses are boned out and the product exported and used for manufacturing meat purposes–for example, sausage–like foods and hamburger. When bulls have outlived their usefulness they, too, are slaughtered, and the boneless meat is ideal for the manufacturing trade because of its strong flavour, low fat content, and its considerable water-holding capacity.