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Title: DETECTION OF MILK RESIDUES BY SCREENING TESTS AND LIQUID CHROMATOGRAPHY FOLLOWING INTRAMAMMARY ADMINISTRATION OF AMOXICILLIN AND PENICILLIN G IN CLINICAL CASES OF BOVINE MASTITIS

Author
item ANDERSON, KEVIN - NORTH CAROLINA STATE UNIV
item Moats, William - Bill
item RUSHING, JOHN - NORTH CAROLINA STATE UNIV
item O'CARROLL, JULIA - NORTH CAROLINA STATE UNIV

Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Testing of milk for B-lactam antibiotics is now mandatory in the United States. A variety of rapid screening tests have been developed for testing milk for antibiotics. There is a need to test both bulk milk and milk from individual cows. There are some reports that the screening tests produce a high incidence of false-positive results, particularly with milk from cows with mastitis which produce abnormal milk. Most evaluations of screening tests have been done with milk from healthy cows. For the present study, cows were selected for treatment which had spontaneously developed mastitis. The screening tests were compared with a specific HPLC method developed in our laboratory. The results showed good agreement between screening test results and HPLC analysis. This indicates that the screening tests can be reasonably reliable for testing milk from individual cows undergoing treatment for mastitis.

Technical Abstract: Six commercial screening tests for B-lactam antibiotics in milk were evaluated for testing milk from individual cows under treatment for mastitis. The cows which had developed mastitis naturally were treated by intramammary infusion with either amoxicillin or penicillin G. Milk samples taken from these cows, before and after treatment, were evaluated for residues by HPLC analysis and by the screening tests. All tests were negative prior to treatment. False positive tests for antibiotics were observed in two of six cows after residue levels by HPLC analysis had fallen below violative levels. Milk from these two cows was abnormal in appearance and had elevated somatic cell counts. The screening tests are reliable for testing milk from individual cows which is not grossly abnormal.