Comparison of a radioimmunoassay (Charm II) test with high-performance liquid chromatography for detection of oxytetracycline residues in milk samples from lactating cattle

William A. Moats From the Meat Science Research Laboratory, USDA, Beltsville, MD 20705 (Moats), and the Department of Food Animal and Equine Medicine, College of Veterinary Medicine (Anderson), and Departments of Food Science (Rushing) and Animal Science (Wesen), College of Agricultural and Life Sciences, North Carolina State University, Raleigh, NC 27606.

Search for other papers by William A. Moats in
Current site
Google Scholar
PubMed
Close
 PhD
,
Kevin L. Anderson From the Meat Science Research Laboratory, USDA, Beltsville, MD 20705 (Moats), and the Department of Food Animal and Equine Medicine, College of Veterinary Medicine (Anderson), and Departments of Food Science (Rushing) and Animal Science (Wesen), College of Agricultural and Life Sciences, North Carolina State University, Raleigh, NC 27606.

Search for other papers by Kevin L. Anderson in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
,
John E. Rushing From the Meat Science Research Laboratory, USDA, Beltsville, MD 20705 (Moats), and the Department of Food Animal and Equine Medicine, College of Veterinary Medicine (Anderson), and Departments of Food Science (Rushing) and Animal Science (Wesen), College of Agricultural and Life Sciences, North Carolina State University, Raleigh, NC 27606.

Search for other papers by John E. Rushing in
Current site
Google Scholar
PubMed
Close
 PhD
, and
Donald P. Wesen From the Meat Science Research Laboratory, USDA, Beltsville, MD 20705 (Moats), and the Department of Food Animal and Equine Medicine, College of Veterinary Medicine (Anderson), and Departments of Food Science (Rushing) and Animal Science (Wesen), College of Agricultural and Life Sciences, North Carolina State University, Raleigh, NC 27606.

Search for other papers by Donald P. Wesen in
Current site
Google Scholar
PubMed
Close
 PhD

Click on author name to view affiliation information

SUMMARY

A radioimmunoassay test for tetracyclines (Charm II) was compared with high-pressure liquid chromatography (hplc) for detection of oxytetracycline (otc) residues in milk samples from individual lactating cows. Oxytetracycline was administered by 1 of 3 routes (IV, IM, or intrauterine) to 21 lactating dairy cows. A total of 292 duplicate milk samples were collected from milkings before and through 156 hours after otc administration. Concentration of otc in these samples was determined by use of the Charm II test and an hplc method with a lower limit of quantitation, approximately 2 ng of otc/ml. Samples were also classified with respect to presence of otc residues relative to the fda safe concentration (< 30 ng/ml), using the Charm II (by control point determination) and hplc methods.

There was a significant (P < 0.05) difference between test methods in classification of milk samples with respect to presence or absence of otc at the fda safe concentration. A total of 48 of the 292 test results (16.4%) did not agree. Using the hplc test results as the standard with which Charm II test results were compared, 47 false presumptive-violative test results and 1 false presumptive-nonviolative Charm fi test result (a sample containing 31 ng of otc/ml, as evaluated by hplc) were obtained. The samples with false presumptive-violative Charm fi results contained < 30 ng of otc/ml, as evaluated by hplc.

In some respects, the Charm H test performed appropriately as a screening test to detect otc residues in milk samples from individual cows. However, the tendency for the test to yield presumptive-violative test results at otc concentrations lower than the fda safe concentration (as evaluated by hplc), suggests that caution should be exercised in using the test as the sole basis on which a decision is made to reject milk. As indicated by the manufacturer, presumptive-violative Charm II test results should be confirmed by additional testing. Although not specifically evaluated, the tendency for misclassification of milk samples as presumptive-violative by the Charm II test may or may not occur in commingled milk, compared with milk samples from individual cows.

SUMMARY

A radioimmunoassay test for tetracyclines (Charm II) was compared with high-pressure liquid chromatography (hplc) for detection of oxytetracycline (otc) residues in milk samples from individual lactating cows. Oxytetracycline was administered by 1 of 3 routes (IV, IM, or intrauterine) to 21 lactating dairy cows. A total of 292 duplicate milk samples were collected from milkings before and through 156 hours after otc administration. Concentration of otc in these samples was determined by use of the Charm II test and an hplc method with a lower limit of quantitation, approximately 2 ng of otc/ml. Samples were also classified with respect to presence of otc residues relative to the fda safe concentration (< 30 ng/ml), using the Charm II (by control point determination) and hplc methods.

There was a significant (P < 0.05) difference between test methods in classification of milk samples with respect to presence or absence of otc at the fda safe concentration. A total of 48 of the 292 test results (16.4%) did not agree. Using the hplc test results as the standard with which Charm II test results were compared, 47 false presumptive-violative test results and 1 false presumptive-nonviolative Charm fi test result (a sample containing 31 ng of otc/ml, as evaluated by hplc) were obtained. The samples with false presumptive-violative Charm fi results contained < 30 ng of otc/ml, as evaluated by hplc.

In some respects, the Charm H test performed appropriately as a screening test to detect otc residues in milk samples from individual cows. However, the tendency for the test to yield presumptive-violative test results at otc concentrations lower than the fda safe concentration (as evaluated by hplc), suggests that caution should be exercised in using the test as the sole basis on which a decision is made to reject milk. As indicated by the manufacturer, presumptive-violative Charm II test results should be confirmed by additional testing. Although not specifically evaluated, the tendency for misclassification of milk samples as presumptive-violative by the Charm II test may or may not occur in commingled milk, compared with milk samples from individual cows.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 44 44 9
PDF Downloads 24 24 1
Advertisement