When it comes to the current controversy over antibiotic use on farm animals, milk is in a special category.
Lactating cows, unlike hogs, cattle or chickens that are raised for their meat, don't receive antibiotics unless they are actually sick. That's because drug residues immediately appear in the cow's milk — a violation of food safety rules.
Milk shipments are tested for six of the most widely used antibiotics, and any truckload that tests positive is rejected. So when cows are treated, farmers discard their milk for several days until the residues disappear.