Meat from a dairy cow slaughtered for food was found to be "adulterated" after testing of the cow's kidney revealed the presence of 0.47 parts per million of penicillin, according to a warning letter from the U.S. Food and Drug Administration last month. The acceptable maximum is 0.05 parts per million.

Kronebusch Farms, Inc., in Altura, Minn. also failed to keep complete treatment records for medicated animals, the FDA found.

A message has been left for president and owner Daniel Kronebusch.

Click here to browse all the agency's warning letters.