<P> Dairy farming, like many other livestock raring, can be split into intensive and extensive management systems . </P> <P> 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 of which the farm is situated . </P> <P> 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 . A cow's gestation period is approximately nine months . Newborn calves are removed 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 . </P> <P> 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 four and marketed for beef . 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 . These animals may be sold due to reproductive problems or common diseases of milk cows such as mastitis and lameness . </P>

Do cows have to be impregnated to produce milk