All dairy cows are forcibly impregnated every year to keep producing milk, calves are removed from their mother immediately after being born, usually not far away, so they both are able to hear one another, but not able to be together (as not to "waste" the milk used for human consumption). Male calves or female calves not fit for milk production are either sent to the slaughterhouse after gaining veal slaughter weight (when max 2 years old), or are killed immediately.
Cow's life is shortened by the milk production, usually from 20-25 years (48 is the record) to the industry's max of 5-6 years.
All dairy cows are then killed in the slaughterhouse and if pregnant, the fetus is extracted (they cut dead mother's belly and let it fall on the floor) and harvested for bovine serum (usually with cardiac puncture, wherein a needle is inserted into its heart and it's bled out to death).