By Steven C. Murphy, Senior Extension Associate
Cows get sick just like humans. Depending on the illness, antibiotics and other drugs may be administered by dairy producers and veterinarians to help improve the health of the cow. Depending on the drug used, there is a possibility of it being passed into the treated cow’s milk, which raises the concern for the possibility of animal drug residues getting into the milk supply and eventually to the consumers. This risk of drug residues getting in the cows milk depends on the type of drug, how it is administered and the ability of the drug to stay in the cows system. These factors will influence the “withdrawal times” needed to prevent contaminating the farm bulk milk, where milk from a treated cow is not added to bulk tank. While there are a wide range of drugs that might be used on dairy farms, some are more commonly used than others. Currently all loads of Grade “A” raw milk are tested at receiving for beta-lactam (penicillin family) antibiotics, which are considered the most commonly used drugs. This requirement is covered in Appendix N of the Pasteurized Milk Ordinance (PMO) and has been very effective in preventing beta-lactam residues in milk by encouraging producers to be diligent in following procedures that protect the milk supply. According to the 2014 fiscal report of the National Drug Residue Data Base, only 0.014% of 3,147,302 tanker loads of milk tested positive. With screening of the raw milk at receiving, there were 0.0% positive tests of over 37,700 samples of pasteurized milk and milk products reported.
While producer management tools and the Appendix N testing program have been instrumental in reducing the risk of beta-lactam drugs being found in the milk supply, other drugs that may be used on the farm have recently come into question in regard to the possibility of residues in milk. This in part was raised due to findings that antibiotics were present in a small percentage of tissue samples (e.g., meat, kidney) tested from culled dairy cows that are sent to slaughter. Based on these findings the Food & Drug Administration (FDA) initiated a Milk Sampling Survey where they tested the milk from 953 farms that were “tissue residue violators” and over 959 random control farms for 31 different drugs. Based on the results of the over 1,900 farms sampled, they found only 16 positives, with florfenicol as the most common drug found.
Along with this sample testing survey, FDA also initiated a “Multi-criteria-Based Ranking Model for Risk Management of Animal Drug Residues in Milk.” The purpose of this FDA assignment was to determine if based on risk, the dairy industry should be testing for other drugs beyond the beta-lactams. In this project, FDA evaluated 54 animal drugs potentially used in the dairy industry, and assigned a risk ranking based on:
- the likelihood that the drug will be administered to lactating dairy cows;
- the likelihood that, following administration, drug residues would be present in bulk milk
- the relative extent to which consumers could be exposed to the drug residue by drinking or eating milk and milk products; and
- the potential for a human health hazard given exposure to the drug residue.
The group of animal drugs included in the model, were ranked from a food safety perspective on the basis of an overall weighted score. Drugs in eight different classes ranked among the top 20 highest-scoring drugs. These eight classes include beta-lactam antibiotics, antiparasitics, macrolides, aminoglycosides, nonsteroidal anti-inflammatory drugs (NSAIDs), sulfonamides, tetracyclines, and amphenicols. This risk assessment is currently open to public comment. While this model assigns a “risk ranking” to these drugs, it does not imply that consumers of dairy products are specifically at risk. It primarily serves as a basis for considering additional testing for animal drugs in milk, to reduce the risk of exposure to animal drug residues. Based on current knowledge, the presence of drug residues in milk is very low and there have been no documented illnesses associated with drug residues in milk. However, preventing illegal residues in milk is essential for public health and the image of the dairy industry.
As this information from FDA has just become public, drug residues were the “hot” topic the National Conference on Interstate Milk Shipments (NCIMS), which just met for their 35th conference in Portland, OR April 24-29, 2015. The NCIMS, in a cooperative effort with FDA, state regulatory agencies and the dairy industry, works to update the PMO and other regulations relative to the Grade “A” Milk program. Several proposals were submitted to the NCIMS conference that pertained to testing of drug residues in milk beyond the current requirements of Appendix N, which primarily addresses the beta lactams. These included proposals to initiate testing for the additional seven families that were ranked highest in FDA’s risk-ranking model listed above. Rather than immediately requiring additional testing, the proposal that passed at the conference was to develop a “pilot program” that would evaluate the process as to how additional testing would be implemented by the industry and state regulators, including determination of what drugs, at what frequency and by what test.
Currently, one of the challenges of testing for other drugs is that there are limited test kits that have been evaluated and accepted by FDA and the NCIMS beyond those for beta-lactam (e.g. the Charm II is the only test approved or tetracyclines and sulfa drugs), although there are several rapid test kits available that have not been evaluated (e.g., Charm ROSA and IDEXX SNAP formats). Currently there are only validated methods for beta-lactams, flunixin, sulfa drugs and tetracycline’s, which are outlined in the FDA Memorandum M-a-85. It is likely that the pilot program will have drug residue test kit manufacturers seeking official approval for some of their formats, but this can be a lengthy process. Another proposal at the NCIMS that was passed addressed the specific procedures for how a dairy plant can screen for drugs other than beta-lactams using a method that is currently not evaluated and accepted by the FDA and NCIMS. This clarifies the procedures that dairy companies must use when testing for other drugs, which may be at the request of a customer or based on their own standards. NY State has already worked with dairy companies to ensure similar procedures have been followed. While these proposals were passed, they do not become regulation until FDA concurs and are formally published.
While the potential for drug residues in milk is a “hot” topic, most dairy farmers are very good at preventing contamination of milk with illegal drugs. Best practices start at the farm with good understanding of proper drug use and continued communication between veterinarians and producers. The National Dairy Farm Program and the National Milk Producers Federation (NMPF) publishes the Milk and Dairy Beef Drug Residue Prevention; Producer Manual of Best Management Practices, which is an excellent guide to producer best practices that provides updated information on drugs that might be used on the farm and procedures to avoid residues in milk.
Links
National Drug Residue Data Base:
http://www.fda.gov/downloads/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/Milk/UCM434757.pdf
FDA Milk Residue Survey:
http://www.fda.gov/AnimalVeterinary/NewsEvents/CVMUpdates/ucm436379.htm
FDA Drug Residue Risk Ranking:
http://www.fda.gov/Food/NewsEvents/ConstituentUpdates/ucm444812.htm?source=govdelivery&utm_medium=email&utm_source=govdelivery
http://www.fda.gov/downloads/Food/FoodScienceResearch/RiskSafetyAssessment/UCM444035.pdf
NDFP/NMPF Milk and Dairy Beef Drug Residue Prevention
http://www.nationaldairyfarm.com/sites/default/files/2015-Residue-Manual-WEB.pdf
