which system of agriculture breeds and raises animals mainly cows for production of milk and diary products.
Answers
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 the 3,100 herds with over 500 cows producing 51% of U.S. milk in 2007.[2] The United Kingdom dairy herd overall has nearly 1.5 million cows, with about 100 head reported on an average farm.[3] In New Zealand, the average herd has more than 375 cows, while in Australia, there are approximately 220 cows in the average herd.[4][5]
The United States dairy herd produced 84.2 billion kilograms (185.7 billion pounds) of milk in 2007,[6] up from 52.9 billion kilograms (116.6 billion pounds) in 1950,[7] yet there were only about 9 million cows on U.S. dairy farms—about 13 million fewer than there were in 1950.[7] 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 10,257 kilograms (22,613 pounds) of milk per cow that contains 3.9% butter fat and 3.2% protein.[8]
Dairy farming, like many other livestock raring, can be split into intensive and extensive management systems.[9]
Intensive systems focus towards maximum production per cow in the herd. This involve 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 are 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 depends on the climate and available land of the region in which the farm is situated.[9]
To maintain lactation, a dairy cow must be bred and produce calves.[10] 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.[11] A cow's gestation period is approximately nine months.[12] Newborn calves are separated from their mothers quickly, usually within three days, as the mother/calf bond intensifies over time and delayed separation can cause extreme stress on both cow and calf.[13]
Domestic cows can live to 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.[12][14] In 2014, approximately 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.[15] These animals may be sold due to reproductive problems or common diseases of milk cows such as mastitis and lameness.[14]