Cowside antibiotic residue testing.

Detectable concentrations of antibiotic residues in milk supplies are illegal. They interfere with manufacturing of some dairy products, may cause hypersensitivity or resistance to drug therapy in humans, and are perceived by consumers as undesirable. Antibiotics are used for intramammary, intramuscular, oral, or reproductive therapy to counter acute or subacute diseases. Residues can result for many reasons, including poor records of treatment, failure to observe recommended label withdrawal time, prolonged drug clearance, treated animal identification problems, products not used according to label directions, lack of advice on withdrawal period, and others. Several effective and useful on-farm residue screening tests are available and should be used to monitor cows treated with an antibiotic for any reason. Herds that use drugs without label directions or that do not follow label directions should find these tests valuable. Producers must understand how to interpret the results of these tests. Also, dairy farmers must recognize if the selected test method is capable of detecting those antibiotics in use and what are to be monitored.