Regulators to test milk for drug residues

Prior tissue residues could determine whose milk is tested
Published on March 01, 2011
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Federal regulators want to know whether illegal drug residues found in some dairy cows sent to slaughter can also be found in milk.

The Food and Drug Administration had planned to collect about 900 milk samples, starting in mid-January, with samples coming from dairies chosen because drug residues had previously been identified in the meat of their dairy cows, said Dr. William T. Flynn, senior adviser for science policy at the FDA Center for Veterinary Medicine. The sampling was delayed after the FDA received feedback from state regulators, milk producers, and dairy processors, and the agency plans to continue working with stakeholders while analyzing the testing protocol, he said. 

Dairy cows

"The primary objective of the milk sampling plan is to determine whether the practices that led to drug residues in tissues of slaughtered dairy cattle might also cause drug residues to be present in milk," Dr. Flynn said. "However, as previously mentioned, the specific approach for conducting the sampling plan and responding to the results are still under discussion."

Adult dairy cattle account for about 8 percent of U.S. cattle slaughtered for beef and 67 percent of illegal residues in tissue, FDA information states. Agency officials had planned to test milk from farms that had some of the most egregious violations in tissue samples.

Milk tankers are routinely tested for beta-lactam antimicrobials but not for some other drugs, such as sulfonamide antimicrobials and anti-inflammatory drugs, FDA information states.

Agriculture secretaries and commissioners from 10 states—Connecticut, Delaware, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont—signed a Dec. 29 letter to the FDA that expressed concerns that the milk testing could disrupt the flow of milk to markets, that state regulators were not adequately consulted about the program, and that the proposed tests could create uncertainty for producers if the FDA were to obtain positive results.

Lorraine S. Merrill, New Hampshire's agriculture commissioner, said state agriculture departments typically work with the FDA on developing and implementing projects such as the proposed testing. But her department first learned about the proposal through a letter from a dairy cooperative, indicating producers found out about the testing before state regulators.

Dr. Stephen K. Crawford, New Hampshire's state veterinarian, said the sampling program proposed by the FDA would have presented challenges to state regulators and the industry. Dr. Crawford previously worked as a dairy practitioner, and he said the interaction between veterinarians and producers, as well as existing milk testing, provide controls to keep residues out of dairy products.

Merrill said the plan also could have caused economic losses, logistic problems, and environmental challenges if processors declined to take milk from tested farms until test results were returned, forcing dairies to dump milk produced over multiple days, regardless of whether their products contained residues. Dairies typically have storage capacity for 24 or 48 hours of production, and milk needs to be pasteurized within 48 hours to maintain its quality and shelf life, she said.

The letter from the agriculture secretaries and commissioners additionally expressed concern that residues from bob veal calves, which are a product of the dairy industry, and a mix of cows contributing and not contributing to the milk supply were considered in determining that residues may be occurring in milk. However, Dr. Flynn said the FDA's sampling plan has focused only on dairy farms selected on the basis of previous residue violations in tissues from adult dairy cows.

The sampling is intended to give the FDA objective data and ensure problems are mitigated through education and enforcement, Dr. Flynn said. He noted that the few producers with tissue residue violations are part of an otherwise compliant industry, and the FDA wants to maintain public confidence in dairy products.

Dr. Flynn indicated tissue residue violations are often the product of failures to keep treatment records, identify treated animals, follow withdrawal times indicated on labels, follow dosage instructions on labels, use the appropriate treatment duration, or administer drugs through approved routes.