http://www.factoryfarming.com/dairy.htmRegardless of where they live, however, all dairy cows must give birth in order to begin producing milk. Today, dairy cows are forced to have a calf every year. Like human beings, cows have a nine-month gestation period, and so giving birth every twelve months is physically demanding. The cows are also artificially re-impregnated while they are still lactating from their previous birthing, so their bodies are still producing milk during seven months of their nine-month pregnancy.
With genetic manipulation and intensive production technologies, it is common for modern dairy cows to produce 100 pounds of milk a day — ten times more than they would produce naturally. As a result, the cows' bodies are under constant stress, and they are at risk for numerous health problems.
Approximately half of the country's dairy cows suffer from mastitis, a bacterial infection of their udders. This is such a common and costly ailment that a dairy industry group, the National Mastitis Council, was formed specifically to combat the disease. Other diseases, such as Bovine Leukemia Virus, Bovine Immunodeficiency Virus, and Johne's disease (whose human counterpart is Crohn's disease) are also rampant on modern dairies, but they commonly go unnoticed because they are either difficult to detect or have a long incubation period.
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In a healthy environment, cows would live in excess of twenty-five years, but on modern dairies, they are slaughtered and made into ground beef after just three or four years. The abuse wreaked upon the bodies of dairy cows is so intense that the dairy industry also is a huge source of "downed animals" — animals who are so sick or injured that they are unable to walk even stand. Investigators have documented downed animals routinely being beaten, dragged, or pushed with bulldozers in attempts to move them to slaughter.
http://www.farmsanctuary.org/media/pr_dairy.htm"The dairy industry's promotional images depicting happy cows whiling away their time in shaded pastures couldn't be further from the reality of dairy production in the United States today," said Gene Bauston, president of Farm Sanctuary. "Unfortunately, this report reveals that trends are falling further in-line with profit motive, leaving little to no regard for the welfare of the animals that are forced to live out their short lives within this industry. While scientists in Europe have led the way to studying how to improve dairy cow welfare, U.S. scientists have led the way in researching milk production efficiency."