Dairy cattle (also called dairy cows) are cattle bred for the purpose of producing large quantities of milk, from which dairy products are made. Dairy cattle are of the genus Bos and usually the species Bos taurus.
Prior to the 1930s, cattle were generally raised for multiple uses, including dairy, beef, and sometimes work as well. The same stock was often used for both meat and milk production. In the 20th century, the industry began to specialize its herds, favoring cattle breeds specifically bred for cows producing milk, most notably the Holstein Friesian. The other main contemporary dairy-focused breeds are the Jersey, Brown Swiss, Guernsey, and Ayrshire.
Management
Dairy cows may be found either in herds or dairy farms, where dairy farmers own, manage, care for, and collect milk from them, or on commercial farms. Herd sizes vary around the world depending on landholding culture and social structure. The United States has an estimated 9 million cows in around 75,000 dairy herds, with an average herd size of 120 cows. The number of small herds is falling rapidly, with 51% of U.S. milk in 2007 produced by the 3,100 herds with over 500 cows. The United Kingdom dairy herd overall has nearly 1.5 million cows, with about 100 head reported on an average farm."Milk and Milk Products, UK Dairy Industry ," Department for Environment Food and Rural Affairs 3 September 2010. In New Zealand, the average herd has more than 375 cows, while in Australia, there are approximately 220 cows in the average herd."New Zealand Dairy Statistics 2009–2010 ," Dairy NZ 2010."Industry Statistics ," Dairy Australia. Retrieved 5 January 2011.
The United States dairy herd produced of milk in 2007,. up from in 1950, yet there were only about 9 million cows on U.S. dairy farms—about 13 million fewer than there were in 1950. The top breed of dairy cow within Canada's national herd category is Holstein, taking up 93% of the dairy cow population, have an annual production rate of of milk per cow that contains 3.9% butter fat and 3.2% protein.
Dairy farming, like many other livestock-rearing methods, can be split into intensive and extensive management systems.
Intensive systems focus towards maximum production per cow in the herd. This involves formulating their diet to provide ideal nutrition and housing the cows in a confinement system such as free stall or tie stall. These cows are housed indoors throughout their lactation and may be put to pasture during their 60-day dry period before ideally calving again. Free stall-style barns involve cattle loosely housed where they can have free access to feed, water, and stalls, but are moved to another part of the barn to be milked multiple times a day. In a tie-stall system, the milking units are brought to the cows during each milking. These cattle are tethered within their stalls with free access to water and feed provided. In extensive systems, cattle are mainly outside on pasture for most of their lives. These cattle are generally lower in milk production and are herded multiple times daily to be milked. The systems used greatly depend on the climate and available land of the region in which the farm is situated.
To maintain lactation, a dairy cow must be bred and produce calves. Depending on market conditions, the cow may be bred with a "dairy bull" or a "beef bull." Female calves (heifers) with dairy breeding may be kept as replacement cows for the dairy herd. If a replacement cow turns out to be a substandard producer of milk, she then goes to market and can be slaughtered for beef. Male calves can either be used later as a breeding bull or sold and used for veal or beef. Dairy farmers usually begin breeding or artificially inseminating heifers around 13 months of age.Department of Animal Science," Cattle Teaching and Research Center ," Michigan State University 4 November 2010. A cow's gestation period is about nine months.Dewey, T. and J. Ng., "Bos taurus," Animal Diversity Web, 2001. Retrieved 13 January 2011. Newborn calves are separated from their mothers quickly, usually within three days. Farmers often argue the mother/calf bond intensifies over time and delayed separation can cause extreme stress on both cow and calf.Dale More et al., "Calf Housing and Environments Series," Veterinary Medicine Extension December 2010. However, a 2019 review found the effects on behavior were worsened with earlier cow-calf separation.
Domestic cows can live beyond 20 years, however, those raised for dairy rarely live that long, as the average cow is removed from the dairy herd around age six and marketed for beef. In 2014, roughly 9.5% of the cattle slaughtered in the U.S. were culled dairy cows – cows that can no longer be seen as an economic asset to the dairy farm. These animals may be sold due to reproductive problems or common diseases of milk cows such as mastitis and lameness. Cows are sometimes slaughtered while pregnant. A small market exists for slaughter-free milk, which increases costs but gives spent cows a retirement rather than the slaughterhouse. This method of production has criticized for higher methane emissions and dedicating land to pasturage that could be left fallow or to nature.
Calf Most heifers (female calves) are kept on farm to be raised as replacement heifers, bred to enter the production cycle. Nearly all male calves and any excess female calves are sold on the market, usually at two weeks of age; males fetch a slightly higher price than excess females. Dairy calves sold for meat can be turned into 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, to make them less aggressive. A tiny minority of bull calves, generally descended from elite cows with a proven track record of high lactations, may be put into progeny testing schemes to be considered for a life as a breeding sire.
Most dairy farms separate calves from their mothers within a day of birth to reduce transmission of disease and simplify management of milking cows. 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.
After separation, some 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, and is typically less contaminated than whole milk when handled properly. Some farms pasteurize and feed calves milk from the cows in the herd instead of using replacer. A day-old calf consumes around 5 liters of milk per day.
Cattle are social animals; their ancestors tended to live in matriarchal groups of mothers and offspring. The formation of "friendships" between two cows is common and long lasting. Traditionally individual housing systems were used in calf rearing, to reduce the risk of disease spread and provide specific care. However, due to their social behaviour the grouping of offspring may be better for the calves' overall welfare. Social interaction between the calves can have a positive effect on their growth. It has been seen that calves housed in grouped penning were found to eat more feed than those in single pens, suggesting social facilitation of feeding behaviour in the calves. Play behaviour in pre-weaned dairy calves has also been suggested to help build social skills for later in life. It has been seen that those reared in grouped housing are more likely to become the dominant cattle in a new combination of animals. These dominant animals have a priority choice of feed or lying areas and are generally stronger animals. For these reasons, it has become common practice to group or pair calves in their housing. It has become common in Canada to see paired or grouped housing in outdoor hutches or in an indoor pack penning.
Bull
In traditional agriculture for most of human history, herds needed a bull to keep the cows in lactation and to produce calves. Small-time farmers with just a few cows would sometimes arrange bulls to be rented, transferred, or otherwise shared, as it might not make sense to keep and feed a bull for just a few cows. Still, fewer bulls were needed than cows, so excess bulls in the traditional system were still turned into meat, or castrated to become draft animals as oxen.
A bull kept for direct natural herd breeding might service up to 50 or 60 cows during a breeding season. Any more and the sperm count declines, leading to cows "returning to service" (needing to be bred again). It is also considered good practice to rotate such herd bulls when possible, with agents arranging swaps to prevent inbreeding. When bulls are used directly, young bulls are preferred, as older bulls can have their temperament shift unpredictably.
During the 20th century, the popularity of keeping a bull directly on dairy farms rapidly declined in favor of the use of artificial insemination (AI). Bulls are dangerous and a source of injury to farmers and cows. They can damage fences, and farmers risk disaster if their bull becomes infertile or otherwise unfit for service. Additionally, direct use of bulls makes it easier for diseases to spread through a herd, such as the venereal disease Tritrichomonas foetus. The shift was sudden and dramatic. From the 1930s to the 1990s, the vast majority of dairy farms switched to artificial insemination, with bulls only kept as a rare backup for if AI repeatedly failed.
Specialized dairy breeding farms, rather than production farms, are where breeding sire bulls are generally kept in the new system. These facilities possess the specialized setups for safely raising and monitoring bulls. These bulls provide the semen collected for artificial insemination of dairy cows. A single bull can serve far more cows this way than via traditional breeding, providing economies of scale.
Milk production levels
Selective breeding has greatly changed the milk production rates of modern herds. Most dairy cows now produce much more milk than their young could need in a situation in the wild. While a cow in lactation in the 1800s might be able to "dry" if abandoned by humans, a 21st-century dairy cow would suffer a more severe health crisis if milking is neglected for too long.
Dairy cow production levels peak at around 40 to 60 days after calving. Production declines steadily afterwards until milking is stopped at about 10 months. The cow is "dried off" for about sixty days before calving again. Within a 12 to 14-month inter-calving cycle, the milking period is about 305 days or 10 months long. Among many variables, certain breeds produce more milk than others within a range of around of milk per year.
The Holstein Friesian is the main breed of dairy cattle in Australia, and said to have the "world's highest" productivity, at of milk per year.'Holstein' (AUSTREX website) . Accessed 30 October 2016. The average for a single dairy cow in the US in 2007 was per year, excluding milk consumed by her calves, whereas the same average value for a single cow in Israel was reported in the Philippine press to be in 2009. High production cows are more difficult to breed at a two-year interval. Many farms take the view that 24 or even 36 month cycles are more appropriate for this type of cow.