Antibiotic testing is part of milk collection and management. According to the National Milk Drug Residue database, dairy producers increased the number of antibiotic free milk loads to 99.988% of all loads of milk delivered in 2015.
Source: Hoard’s Dairyman, March 7, 2016.
Every load of milk delivered to dairy processing plants is tested for the presence of antibiotics. Any load that tests positive for drug residues is discarded. It never enters the food chain.