Dairy cattle

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Dairy cattle, generally of the species Bos taurus, are domesticated animals bred to produce large quantities of milk. For general information on milk production see dairy farming.

Contents 1 Modern times 1.1 Dairy farms 1.2 Life of dairy cattle 1.2.1 The bull 1.2.2 The cow 1.2.3 Production levels 1.2.3.1 Embryo transfer 1.2.4 Lifespan 1.2.5 Hormone use 1.2.6 Pesticide use 1.3 Breeds 2 References

[edit] Modern times

Historically, there was less distinction between dairy cattle and beef cattle, with animals of the same species often being used for both meat and milk production. Dairy cattle are now specialized animals, and most of them have been bred specifically to produce large volumes of milk. This milk is made into various products, including cheese, yogurt, butter, ghee, cottage cheese, whey, and ice cream, and is consumed around the world.

[edit] Dairy farms

Dairy cattle may be found in herds on farms where dairy farmers own, manage, care for, and collect milk from them.

These herds range in size from small farms of fewer than five cows to large conglomerates of 25,000 cows or more. The average dairy farmer in the United States manages about one hundred cows but this varies from an average of 800 cows in California to under 80 in the North East states. Herd sizes vary around the world depending on landholding culture and social structure. In many European countries the average herd size is well below 50. In the UK it is over 100 in New Zealand 350 and Australia 280. Dairy farming is closely linked to areas settled by North Europeans and these areas (Europe, N. America, Australasia) dominate commercial dairy production and trade in dairy products. Between 1959 and 1990, US milk production doubled while the number of dairy cows declined 40 percent. ^[1]

[edit] Life of dairy cattle

Pure bred heifer calves are usually reared as herd replacements. Sales of crossbred heifers and bull calves are subject to the demand for beef animals within transport range of the farm. Surplus calves are generally sold at two weeks of age and bulls may fetch a premium over heifers due to their size and potential. Calves may be sold for veal, or for one of several types of beef production, depending on available local crops and markets. Such bull calves may be castrated if turnout onto pastures is envisaged, in order to render the animals less aggressive. Purebred bulls from elite cows may be put into progeny testing schemes to find out whether they might become superior sires for breeding. Such animals may become extremely valuable.

Most dairy farms separate calves from their mothers within a day of birth to reduce bonding. Studies have been done allowing calves to remain with their mothers for 1, 4, 7 or 14 days after birth. Cows whose calves were removed longer than one day after birth showed increased searching, sniffing and vocalizations. However, calves allowed to remain with their mothers for longer periods showed weight gains at three times the rate of early removals as well as more searching behavior and better social relationships with other calves. ^[2][3]

After separatation, most young dairy calves subsist on commercial milk replacer, a feed based on dried milk powder. Milk replacer is an economical alternative to feeding whole milk because it is cheaper, can be bought at varying fat and protein percentages. A day old calf consumes around 2 liters of milk per day.

[edit] The bull

Bulls with high genetic potential may be reared for breeding purposes.

Herd bulls, are bulls kept on the farm to provide natural breeding for the herd. A bull may service up to 50 or 60 cows during a continuous breeding period. Any more and the semen will become too diluted, leading to cows "returning to service". A herd bull may only stay for one season since over two years old their temperament becomes too unpredictable.

Since the 1950s, artificial insemination, or AI, is used at most dairy facilities due to its predictible results.

[edit] The cow

Dairy cows cannot produce milk until after calving. Most farmers begin breeding heifers as early as fourteen months of age. A cow's gestation period is approximately nine months, so most heifers give birth at around two years of age.

[edit] Production levels

A cow will produce large amounts of milk over its lifetime. Certain breeds produce more milk than others; however, different breeds produce within a range of around 4,000 to over 10,000 kg of milk per annum. The average for dairy cows in the US in 2005 was 8,800 kg (19,576 pounds).

Production levels peak at around 40 to 60 days after calving.^[4] The cow is then bred. Production declines steadily afterwards, until, at about 305 days after calving, the cow is 'dried off', and milking ceases. About sixty days later, one year after the birth of her previous calf, a cow will calve again. High production cows are more difficult to breed at a one year interval. Many farms take the view that 13 or even 14 month cycles are more appropriate for this type of cow.

Dairy cows may continue to be economically productive for many lactations. Ten or more lactations are possible. The chances of problems arising which may lead to a cow being culled are however, high; the average herd life of US Holsteins is today fewer than 3 lactations. This requires more herd replacements to be reared or purchased. Over 90% of all cows are culled for 4 main reasons:

• Infertility - failure to conceive and reduced milk production.

Cows are at their most fertile between 60 and 80 days after calving. Cows remaining "open" (not with calf) after this period become increasingly difficult to breed, which may be due to poor health. Milk fever, failure to expel the afterbirth from a previous pregnancy, luteal cysts, or metritis, an infection of the uterus, are common.

• Mastitis - persistent and potentially fatal mammary gland infection, leading to high somatic cell counts and loss of production.

Mastitis is recognized by a reddening and swelling of the infected quarter of the udder and the presence of whitish clots or pus in the milk. Treatment is possible with long-acting antibiotics but milk from such cows is not marketable.

• Lameness - persistent foot infection or leg problems causing infertility and loss of production.

High feed levels of highly digestible carbohydrate cause acidic conditions in the cow's rumen. This leads to laminitis and subsequent lameness, leaving the cow vulnerable to other foot infections and problems which may be exacerbated by standing in feces or water soaked areas.

• Production - some animals fail to produce economic levels of milk to justify their feed costs.

Production below 12 to 15 liters of milk per day are not economically viable.

Herd life is strongly correlated with production levels.^{[citation needed]} Lower production cows live longer than high production cows, but may be less profitable. Cows no longer wanted for milk production are sent to slaughter. Their meat is of relatively low value and is generally used for processed meat.

[edit] Embryo transfer

More recently, embryo transfer has been used to enable the multiplication of progeny from elite cows. Such cows are given hormone treatments to produce multiple embryos. These are then 'flushed'. 7-12 embryos are consequently removed from these donor cows and transferred into other cows who serve as surrogate mothers. The result will be between 3 and 6 calves instead of the normal single, or rarely, twins. This process is called embryo transfer.

[edit] Lifespan

The natural lifespan of a cow is approximately 25 years, however dairy cattle are rarely kept longer than five years prior to slaughter. ^[5] Herd life is strongly correlated with production levels. Lower production cows live longer than high production cows, but are less profitable so are sent for slaughter at a younger age.

Approximately 17 percent of the US beef supply comes from spent dairy cattle, or those cows who are no longer economically viable for milk production. These animals may be sold due to common diseases of milk cows including mastitis, a bacterial udder infection, foot rot, from standing long periods of time in manure, an inability to stand due calcium depletion from years of intensive milking, and Johne's disease. Johne’s disease may be transmissible to humans as Chron’s disease. ^[6]

The use of spent dairy cows received negative publicity after a Humane Society of the United States undercover video showing a downer cow being illegally mistreated at a California slaughter facility.

[edit] Hormone use

More recently, embryo transfers have enabled the production of multiple progeny from specific cows. These cows are given hormone treatments to produce multiple embryos which are then 'flushed' to be later implanted into other cows who serve as surrogate mothers.

To be economically viable, hormones have to be administered at specific times to dairy cattle to induce ovulation. Frequently, for economic considerations, these drugs are also used to synchronize a group of cows to ovulate simultaneously. The hormones Prostaglandin, Gonadotropin Releasing Hormone, and Progesterone are used for this purpose and sold under the brand names Lutalyse, Cystorelin, Estrumate, Factrel, Prostamate, Fertagyl. Insynch, and Ovacyst. They may be administered by injection, insertion or mixed with feed.^[7]

About 30% of dairy cows in the United States are injected with Bovine somatotropin, also called recombinant bovine somatotropin (rBST), recombinant bovine growth hormone (rBGH), or artificial growth hormone. The use of this hormone increases milk production from 11%-25%, but also increases the likelihood of cattle developing mastitis, reduction in fertility and lameness. The U.S. Food and Drug Administration (FDA) has ruled that rBST is harmless to people, although critics point out increased levels of insulin-like growth factor 1 (IGF-1) in milk produced using this hormone. The use of rBST is banned in Canada, parts of the European Union, Australia and New Zealand.

[edit] Pesticide use

A survey of the primary dairy producing areas in the US indicated that 13 percent of lactating animals were treated with insecticides permethrin, pyrethrin, coumaphos, and dichlorvos primarily by daily or every-other-day coat sprays. Workers, particularly in stanchion barns, may be exposed to higher than recommended amounts of these pesticides. ^[8]

[edit] Breeds

In the United States, dairy cattle are divided into seven major breeds. These are the: Holstein-Friesian, Red and White Holstein, Brown Swiss, Guernsey, Ayrshire, Jersey, Milking Shorthorn.

Many other breeds are used nearly exclusively for Beef, or for both dairy and beef purposes.

[edit] References