Dairy cows can be found either in herds or dairy farms where dairy farmers very own, manipulate, take care of, and accumulate milk from them, or on commercial farms. Herd sizes vary round the sector depending on landholding subculture and social structure. the united states has an expected 9 million cows in round 75,000 dairy herds, with an average herd length of one hundred twenty cows. The quantity of small herds is falling swiftly with the three,100 herds with over 500 cows producing fifty one% of U.S. milk in 2007. the UK dairy herd ordinary has nearly 1.five million cows, with approximately 100 head reported on an average farm. In New Zealand, the average herd has greater than 375 cows, at the same time as in Australia, there are about 220 cows within the common herd. To hold lactation, a dairy cow should be bred and produce calves. relying on market conditions, the cow can be bred with a "dairy bull" or a "beef bull." woman calves (heifers) with dairy breeding can be stored as substitute cows for the dairy herd. If a substitute cow seems to be a substandard manufacturer of milk, she then is going to market and can be slaughtered for pork. Male calves can either be used later as a breeding bull or offered and used for veal or pork. Dairy farmers normally begin breeding or artificially inseminating heifers round 13 months of age.[ A cow's gestation period is about nine months.newborn calves are separated from their moms quickly, commonly inside three days, as the mom/calf bond intensifies over the years and delayed separation can purpose intense stress on both cow and calf