Milk drug residue concerns

today go beyond penicillin

Concern about antibiotics in milk started in the 1970s when cheese makers noticed the starters in their cheese process were being inhibited.

By the 1980s, that concern had grown to one of public health. Officials wanted to make sure that hypersensitive people were not exposed to specific antibiotics - specifically penicillin.

Pamela Ruegg, a veterinarian and milk quality expert with the University of Wisconsin, notes that in 2009 there were 861 tankers of milk out of a total of 3.31 million tankers that tested positive for drug residues - a very small percentage.

While the problem with penicillin-type drug residues continues at a very low level, authorities are now taking aim at other drugs in the veterinary arsenal because they have been showing up in the tissues of cull dairy cows.



Cull dairy cows

major source

Ruegg spoke to a large crowd of dairy producers at the 15th annual Arlington Dairy Day at the UW Arlington Agricultural Research Station Dec. 8. She said the beef industry and regulators now consider cull dairy cows a major source of antibiotic residues.

Today's concern revolves around maintaining global markets for our products and there is growing concern about other drugs that have been detected in animal tissue.

In a 2008 federal survey, cull dairy cows were responsible for 44 percent of the total tissue violations at slaughterhouses and bob veal calves - most of which come from dairy farms - were responsible for 46 percent.

"We're really dealing with dual-purpose animals. You are dairy producers but you are also beef producers."

The top violative drug was penicillin, followed by flunixin, sulfamethoxine and desfuroylceftiofur. Ruegg showed her audience how residue data can be found on the web, including the name and address of the farm and its violation history.

"This information's out there and it's not a great source of pride for our industry," she said.



Testing milk samples

The federal Food and Drug Administration (FDA) has been trying to take aim at this problem for several years and had earlier proposed a plan to test milk samples from tissue residue violators for additional drugs.

"The agency got to thinking that if these farms are shipping animals with tissue violations, maybe the milk from their cows has the same drugs in it that we're not testing for." Current milk testing only includes the penicillin drug family.

The dairy industry has been vocal about its concern on various proposed FDA testing plans and now the agency is about to begin those tests. They will test milk from 900 dairy producers who have a history of tissue violations on their cull animals.

Those milk samples will be tested for the residues or metabolites of 26 drugs. In a nod to the industry, which has been concerned about a public perception of milk safety, the agency will also take milk samples from 900 random herds that have no tissue violation history.

The industry is concerned that the public "may not enjoy the perception" created by the testing program and by its eventual results, Ruegg said.

The FDA has agreed to make sure the tests are done in such a way that the farm of origin of each sample is kept secret. With that testing program about to begin, Ruegg said farmers need to redouble their efforts to make sure they use drugs properly.



Mastitis treatment

On most dairy farms the reason for using antibiotics boils down to mastitis treatment. In a study Ruegg and colleagues did in 2005, 88 to 100 percent of the dairy farms surveyed had used antibiotics in the previous 60 days.

They found that 83 percent of the antibiotic use was related to mastitis treatment.

"Antibiotic residues usually occur because of mistakes. Mistakes in recording the information, in identifying the animal or communication mistakes," she said.

In a 2011 survey of 50 Wisconsin dairy herds with over 200 cows, Ruegg found that mastitis was the most common reason for treatment of dairy cows. "We really need to be looking at our mastitis treatments," she said.

Farmers must educate themselves about which drugs can be used for mastitis and which cannot. There are label directions for each drug and they must be followed closely. Some drugs cannot be used at all on lactating dairy cows, even by a veterinarian.

Ruegg noted that any cow over 20 months of age is considered by the FDA to be a "lactating dairy cow" regardless of whether they are milking or not and this affects which drugs can be used on them.

"Know the bug. Know the drug. Know the cow," she said. It's also important to have a strong relationship with a herd veterinarian and develop and use written drug treatment protocols on the farm.

"Read the labels. Read the labels. Read the labels. And follow them," she said.

"And keep records. Keep records. Keep records."