The long-anticipated drug-residue-sampling survey by the U.S. Food and Drug Administration has begun.

According to the National Milk Producers Federation, the survey will involve 900 milk samples from dairy producers who have had a cull dairy cow residue violation in the past, as well as another 900 milk samples from dairies at large.

The idea is to see if there is a correlation between drug residues that may be showing up in the carcasses of cull cows with those that may be showing up in milk. Last September, at the annual meeting of the American Association of Bovine Practitioners, FDA official William Flynn said regulators want to know how cull-cow-tissue violators are doing in comparison to the industry as a whole.

Flynn, who serves as deputy director for science policy at the FDA’s Center for Veterinary Medicine, said the survey would be a “blind” study, meaning that regulators will not be able to tie a specific milk sample back to a specific farm. That is what makes the current initiative a “survey” more than a “regulatory action.”

A year ago, it appeared the FDA would take a more aggressive stance, but it backed off and decided to go the survey route instead.  Read “Survey would be a less-obtrusive approach to drug residues.”

Nevertheless, the National Milk Producers Federation has some concerns.

The FDA will be using testing equipment that is far more sensitive than conventional screening tests, points out Jaime Jonker, vice president of scientific and regulatory affairs for the NMPF. There is the potential for FDA to pick up trace amounts that normally would not be found, including some that are well below the “safe level” established by FDA.

NMPF’s concern is how those trace amounts might be interpreted and reported by FDA.

“We will continue to work with the FDA to see if there is a resolution that can come from this,” Jonker told Dairy Herd Management on Monday.