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Demonstrating Careful Antibiotic Stewardship

July 6, 2017

The rise in antibiotic-resistant bacteria seen in the United States and elsewhere in the world is frequently and unfairly blamed on antibiotic use in agriculture. This is unfortunate because it tends to mask the real problem: misuse of antibiotics in human medicine. The reality is that the vast majority of the bacterial strains with resistance or reduced susceptibility to antibiotics are not foodborne pathogens, indicating that veterinary use of antibiotics is not the leading cause of these resistant bacteria. In the United States, hospital-acquired infections are a major factor in antibiotic resistance.

Nevertheless, antibiotics are a valuable tool in veterinary and human medicine alike, and everyone must be careful stewards of these products. In hindsight, the agriculture community likely contributed to its public perception problem by fighting to hang on to growth promotion uses of antibiotics past the point of no return. But for dairy, veterinarians and farmers strive to limit use of antibiotics important in human medicine, and largely confine such use to treatment of a specific disease for a prescribed length of time. Our industry has a long, proud track record of judicious use and of ongoing efforts to ensure a safe milk supply for consumers, one free of any antibiotic residues.

Starting this month, dairy farmers will have a new opportunity to demonstrate their commitment to proper antibiotic use, as federal and state regulators expand their already extensive screening of the U.S. milk supply. This new drug testing pilot program, which will examine hundreds of thousands of milk tanker loads for the tetracycline class of antibiotics, will further demonstrate that we are serious about being good managers of the pharmaceutical tools available to agriculture.

The debut of the new tetracycline testing program comes two years after the National Conference of Interstate Milk Shipments first proposed the idea at its 2015 conference. In the months that followed, National Milk provided input into how the testing program would best generate meaningful data while working to ensure that it did not become burdensome on farms or processors. 

What happens now is that all Grade “A” plants (those making milk and yogurt products) are expected to participate in the screening. Dairy plants that process cheese and butter may also participate in the process. The pilot program will require that at least one out of every 15 tankers will be screened on a random basis.  Some plants may test every load every day, while others may test every load on a certain day each week. Regardless of the sampling method, a rapid response test will check the loads for the presence of any of these drugs: tetracycline, oxytetracycline and chlortetracycline. During the next 18 months, it’s reasonable to assume that nearly every U.S. dairy farm will have its milk tested, not just those shipping to a Grade “A” plant. 

This new program largely mirrors the ongoing beta lactam screening program, which for decades has checked every single tanker load of milk for the penicillin class of drugs. The findings of that program should reinforce the knowledge that our industry’s combination of education, proactive veterinary treatment and careful record-keeping do a tremendous job in minimizing the chances that any trace levels of antibiotics appear in milk.

In fact, since 1996, the percentage of milk tankers that test positive for the presence of beta lactams dropped from an already small figure, 0.104% (that’s almost 99.9% antibiotic residue-free), down to just 0.011% ( that’s nearly 99.99% antibiotic-free) in 2016.  During this 20-year period, any of the tankers that tested positive for violative residue were dumped, the milk never reaching store shelves. The severe threat of being held financially accountable for the disposal for even just one milk tanker is a powerful incentive to be cautious about using these drugs. The many educational materials offered by our own Farmers Assuring Responsible Management (FARM) Program, especially our drug residue prevention manual, have helped the industry continue improving its great track record.  The new requirement that FARM Program participants have a documented relationship with a veterinarian also helps bolster the oversight of the proper use of these products.

The uses of tetracycline are not the same as beta lactams, however, so farmers must continue to ensure that any administration of the drug doesn’t end up in the milk supply.  In particular, the routine use of powdered tetracycline as a treatment for hairy foot warts can cause violative residues in milk. Farmers should work with vets and hoof trimmers to ensure the drugs are used wisely, and that drug withdrawal times are carefully followed so that milk from any treated cow is disposed of until the antibiotic completely clears her body.

At the end of 2018, FDA will study the pilot program data collected and decide whether to formally require testing for tetracyclines. Even though any milk loads testing positive will be disposed of, any violation matters. We need the data to reflect the prudent use of these products, and beyond that, the responsible treatment of dairy cattle throughout their lives.

Ultimately, routine residue testing isn’t what protects consumers from a sub-standard or unsafe product. The procedures that are followed as the animals are handled and the milk is harvested are what protects consumers. A quick test is only the last step in a much larger and robust management system on farms. All the available evidence to date confirms that our system is working well.  The new pilot program will be one more proof point.