Dairy Cows
Traditional small dairies, located primarily in the northeast and midwest are going out of business. They are being replaced by intensive 'dry lot' dairies which are typically located in the southwest.
Regardless 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, the cow's gestation period is nine months long, and so giving birth every twelve months is physically demanding. The cows are also forced to give milk during seven months of their nine month pregnancy. In a healthy environment, cows would live in excess of 25 years, but on modern dairies, they are slaughtered after just 3 or 4 years and then used for ground beef.
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 in nature. 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 are difficult to detect or have a long incubation period, and they commonly go unnoticed.
A cow eating a normal grass diet could not produce milk at the abnormal levels expected on modern dairies, and so today's dairy cows must be given high energy feeds. The unnaturally rich diet causes metabolic disorders including ketosis, which can be fatal, and laminitis, which causes lameness.
Another dairy industry disease caused by intensive milk production is "Milk Fever". This ailment is caused by calcium deficiency, and it occurs when milk secretion uses calcium faster than it can be replenished in the blood.