The occurrence and detection of antibiotic residues in milk continue to be concerns for the dairy industry. Several steps have been taken to assure the public that the milk supply is safe. Many dairy producers have voluntarily adopted the 10-point "Milk and Dairy Beef Residue Prevention Protocol." This relies on the HACCP concept to "manage out" the hazards by close attention to critical control points. On the regulatory front, increased surveillance and testing have been mandated.
1. Of what significance are low level antibiotic residues?
2. How does one verify the presence of low level residues when official tests are not designed to operate in those low ranges?
The first point was addressed with the establishment by FDA of "safe levels" and tolerance levels of antibiotics in milk. Residues above these levels were considered to be violative, while those below were not considered to be of public health or regulatory significance. The practical difficulty of detecting these residues resides in the accuracy and precision of the newly developed tests. That leads to the second question.
Confirmatory analytical techniques had to be developed in order to verify the results of new screening tests. This was accomplished for most antibiotics.
Evaluation and standardization of these tests remained to be done. Since screening tests had been developed to detect many individual antibiotics and families of antibiotics, regulatory agencies began with the most common antibiotics. Screening tests which detect the beta lactam family of antibiotics were the first to be evaluated.
As we can see from the table, no test regularly detects all the target antibiotics at the "safe" or tolerance level. Some, such as the Delvo-X-Press with ceftiofur or the Charm II with cephapirin, detect residues well below the legal limit and could cause legal milk to be rejected or subjected to further regulatory action. The acceptance of these tests ends the industry option to use other non-evaluated screening tests, including the disc assay, to fulfill regulatory testing requirements
|Charm II Tests2||4.8||9||10||--||4.5||25|
|Charm II Tablet
|Charm Farm Test||5||10||10||--||20||25|
|Delvo Test P||3||10||8||--||8||50|
|Lactek B-L||5||8||10||8||16||50 3|
|Snap Test (Idexx)||5||10||10||--||8||50|
|FDA tolerance or
A producer's Grade "A" permit will be suspended when the regulatory agency is notified of a positive drug residue. After completion of at least one milking (or one milking plus two days for the second violation in a 12 month period), the producer may be reinstated if an official milk sample tests negative. This is provided the Milk and Dairy Beef Residue Prevention Protocol is in place on the farm. Should the protocol not have been instituted, it shall be in place within 30 days from the date of the reinstatement. The third occurrence in a 12-month period requires the two-day suspension and initiation of procedures to revoke the producer's permit.
Industry Supervisors (IS) are designated industry representatives who are trained by state LEO's to perform specific official drug screening tests. They and their "backup supervisors" are to supervise their company's screening program and train IA's.
Industry Analysts (IA) are analysts designated and trained by Industry Supervisors to perform drug residue screening tests. The IA's certification is only valid for the time his Industry Supervisor's certification is valid.
State Laboratory Evaluation Officers (LEO) have attended FDA's test kit workshops are eligible to train Industry Supervisors. They have the responsibility to train and certify industry personnel and laboratories.
Certified Industry Supervisors (CIS) are analysts in an official NCIMS certified laboratory who are certified to perform various tests for regulatory action.
Industry Supervisors, or their designated IA, may screen bulk milk pickup tankers. They may not open a regulatory sample to identify a positive producer. However, a certified analyst or a CIS may split the sample in an NCIMS Certified Laboratory. In order for regulatory action to be taken for or against a producer, it must be based on the results from an NCIMS Certified Laboratory. Laboratories can be certified to do drug testing only.
What about the other antibiotics? The newly approved tests detect only four, or at most, five beta lactams. What about the several other families of antibiotics currently available for use?
What about the problem of overly sensitive tests? All of the approved tests will detect at least one antibiotic at levels below the legal limit. This could cause legal milk to be rejected resulting in severe economic losses for the producer.
What about testing individual cow samples? The new kits were tested and approved for commingled milk samples. The producer does not have at his disposal tests which have been shown to be satisfactory for testing the milk from an individual cow prior to reintroducing her to the milking string.
Antibiotic therapy takes place at the producer level. Nothing the processor or the regulatory agency can do will prevent antibiotic residues from occurring in bulk tank milk, though they may be able to screen out some violative loads. The prevention of antibiotic residues sits squarely on the shoulders of the producer and his veterinarian. It is the producers' management practices and their exercise of control in antibiotic therapy programs which can prevent residues in the milk supply. The penalties for violations are severe. A producer may lose his permit to ship milk and with it his livelihood. Consumers, the industry, and the government are speaking with one voice: "Antibiotic residues are not acceptable in the milk supply and the responsibility lies with the producer — the producer alone."
Dr. Donald P. Wesen passed away on July 25, 1994. His work will be sorely missed by his friends in the dairy industry of North Carolina.
Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age or disability. North Carolina State University, North Carolina A & T State University, U.S. Department of Agriculture, and local governments cooperating.
FOOD SAFETY FSE95-2(1-95)
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