Dairy cattle
Dairy cattle are cattle bred with the ability to produce large quantities of milk, from which dairy products are made. Dairy cattle generally are of the species Bos taurus.
Historically, little distinction was made between dairy cattle and beef cattle, with the same stock often being used for both meat and milk production. Today, the bovine industry is more specialized and most dairy cattle have been bred to produce large volumes of milk.
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. In New Zealand, the average herd has more than 375 cows, while in Australia, there are approximately 220 cows in the average herd.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 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. A cow's gestation period is about nine months. 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. 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. A small market exists for slaughter-free milk, which brings increased costs for both consumers and producers.
Calf
Most heifers are kept on farm to be raised as replacement heifers, bred to enter the production cycle. Market calves are generally sold at two weeks of age and bull calves may fetch a premium over heifers due to their size, either current or 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, to make them 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 can become extremely valuable.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
A bull calf with high genetic potential may be reared for breeding purposes. It may be kept by a dairy farm as a herd bull, to provide natural breeding for the herd of cows. A bull may service up to 50 or 60 cows during a breeding season. Any more and the sperm count declines, leading to cows "returning to service". A herd bull may only stay for one season, as when most bulls reach over two years old their temperament becomes too unpredictable.Bull calves intended for breeding are commonly bred on specialized dairy breeding farms, not production farms. These farms are the major source of stocks for artificial insemination.
Milk production levels
The dairy cow produces large amounts of milk in its lifetime. 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. 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.
Dairy cows may continue to be economically productive for many lactation cycles. In theory a longevity of 10 lactations is possible. The chances of problems arising which may lead to a cow being culled are high, however; the average herd life of US Holstein is today fewer than 3 lactations. This requires more herd replacements to be reared or purchased. Over 90% of all cows are slaughtered for 4 main reasons:
- Infertility – failure to conceive and reduced milk production.
- Mastitis – a persistent and potentially fatal mammary gland infection, leading to high somatic cell counts and loss of production.
- Lameness – persistent foot infection or leg problems causing infertility and loss of production.
- Production – some animals fail to produce economic levels of milk to justify their feed costs.