A source of antibiotic residues in milk
Guard, P.W.; Madeley, J.D.; Symington, W.M.
Veterinary Record 116(11): 302
1985
ISSN/ISBN: 0042-4900 PMID: 3992838 Document Number: 252929
When antibiotics-treated cows are machine milked, the milk is redirected so that it does not enter the bulk tank. When bulk tank milk fails the antibiotics test, it is assumed that the cows are continuing to excrete antibiotics after the recommended withdrawal period. However, a possible source of contamination of bulk milk is the milk release valve which directs milk from the jar to either the bulk tank or discard. This valve may become worn and allow milk from treated cows to contaminate 'down-stream' equipment. In some milking installations, it is not possible to move the valve from 'milk' to 'reject' positions without going through the 'wash' or 'release' positions; this operation may draw up to 400 ml milk into the system and this may be enough to cause the bulk tank to fail the antibiotic test. To avoid this problem, treated cows should be milked last or into a separate cluster and bucket unit.