Using Residue Tests in Support of a Quality Milk Program
Authors: Sischo William M. 
Published: March 2023

The certification process for antibiotic residue tests for raw, comingled bovine milk has been a long and arduous process. In terms of protecting the consumer from antibiotic tainted milk perhaps the process developed by FDA and administered by AOAC International can be deemed a success. Unfortunately for the producer and veterinarian the process has left some problems. First, the tests have not been evaluated in a population context. The number of samples required for certification was small and unlikely to represent the range of bulk or individual milk quality that will be experienced in the field. The quality of the estimates of the population test parameters resulting from the certification is questionable meaning that we will be conducting an uncontrolled field trial when these tests come on line in January 1995. Second, the certification process which focussed on developing convenient tests to be used in the rapid screening of milk by processors allowed tests to be certified that will detect some antibiotics below regulatory tolerance levels and in some cases above tolerance levels. Although there will be some accounting for these discrepancies in the labels for these tests, the presence and use of these tests suggests that producers and veterinarians will be facing the very real probability that legal milk will be dumped and producers penalized for the test's mistake. Third, some AOAC certified tests (approved for bulk milk) will be marketed as farm and cow tests. Although the labels for these tests will explicitly describe their approval for bulk milk only, the implicit message is that the test can be used appropriately for individual animal milk. There will be no data to support use of these test on individual animals and it will be necessary to subject these tests to small sample size protocols to develop some expertise in using these tests on the farm. Additionally we will need to develop an epidemiologic approach in order to effectively interpret test results for the dairy producer. Finally, because the breadth of the testing program will be increasing (the present official test, the Bacillus stearothermophilus disk assay detected only a portion of the 6 beta lactams targeted in the new program) there will be an increase in the number of violations detected beginning January 1995 with no reason other than increased ability to detect the antibiotics that had gone undetected.
We will have to live with these tests and we should make efforts to understand how these tests can be best used. The goal of the dairy industry needs to be towards the continuing production of nutritious, good tasting, and safe milk. Although the tests as they stand today are fraught with problems they should be utilized as necessary as part of a farm Total Quality Management program and within the context of the MDBQAP. They are not intended nor should they ever be used to define a quality product. Milk quality in all its dimensions begins with an on-farm program to promote animal and particularly udder health. When disease does occur alternatives to antibiotics should be employed when possible and if antibiotics become necessary then they should be used in a rational manner. This approach should include on-farm training in handling and administering the drugs, developing treatment protocols to provide guidelines for antibiotic use, and importantly having record keeping and identification systems that track antibiotic use and can be used by every member of the dairy management team to know which animals have been treated. The final link in the system will be the screening kits which will be appropriately used to verify that treated cows for which milk has been held from sale according to the label guidelines is negative for antibiotics and the milk is saleable from that aspect.