The safety of dairy products relies on good farming, processing, transport, and storage practices, along with accurate screening for pathogens and drug residues. Continued advancements in dairy safety are now focused on novel techniques that use gene sequencing, metagenomics, and even image analysis and artificial intelligence (AI) to provide early warning signals of potential problems in an industry that produces one of the safest products in the country.
In 1938, milk-borne outbreaks were responsible for 25 percent of all disease outbreaks attributed to infected foods and contaminated water. By 2015, milk and fluid milk products were associated with less than 1 percent of reported outbreaks, according to the U.S. Public Health Service and FDA Grade “A” Pasteurized Milk Ordinance [PMO] 2015 Revision.
Drug residues in milk have been a concern, and sensitive and accurate analytical methods have been developed to detect and measure the presence of antibiotic residues in dairy products. Under the National Conference on Interstate Milk Shipments (NCIMS) Grade “A” program, state regulatory agencies report milk testing activities to the National Milk Drug Residue Database. In 2012, more than 3.7 million tests were reported to the database, and any milk containing illegal drug residues were not allowed to enter the human food supply.
PMO requires that a milk sample be tested from every bulk tank of raw milk collected at each farm, as well as a sample from every truckload of raw milk arriving at a dairy plant. Samples from every arriving truckload of raw milk are tested for the presence of at least four of six specific beta-lactam drugs: penicillin, ampicillin, amoxicillin, cloxacillin, cephapirin, and ceftiofur. If any test positive, raw milk samples from each farm that supplied the sample for that truckload must be tested.
In addition, the FDA Center for Veterinary Medicine conducted a Milk Drug Residue Sampling Survey, published in 2015, which analyzed raw milk samples from individual dairy farms that had been previously identified as having a drug residue violation in tissues from culled dairy cows at slaughter. These samples were compared to a control group of samples from farms that had not been identified with a previous residue violation. The milk samples were analyzed for antibiotics, non-steroidal anti-inflammatory drugs, and an antihistamine, a total of 31 different drug residues. A positive residue was defined as being at or about 50 percent of the established safe level/tolerance.
Out of the 1,912 total samples, there were 11 confirmed positive milk samples out of 953 (1.15 percent) targeted milk samples, representing 12 confirmed drug residues in the targeted sample group. One sample contained two confirmed drug residues. Among the 959 non-targeted samples, or the control group, there were four confirmed drug residues (0.42 percent). According to the FDA Center for Veterinary Medicine report about this sampling and testing, “the small number of positives in both the targeted and non-targeted groups is encouraging and the FDA continues to be confident in the safety of the U.S. milk supply.”
Additionally, the FDA report called for strengthening the NCIMS drug residue testing program to educate dairy producers on best practices to avoid these residues in both tissue and milk; to utilize the data to, if necessary, include testing for more diverse drug classes in milk; and to consult with state milk regulatory agencies to consider (on a case-by-case basis) collecting milk samples in conjunction with investigating illegal drug residues in tissue involving cull dairy cattle.
Analyzing the Microbiome
Investigators at the University of California, Davis, are taking dairy safety another step forward by identifying the raw-milk microbes, or the level of bacterial diversity that is found in shipments of raw milk that arrive at participating processing facilities in California. The researchers sampled and analyzed milk from 899 tanker trucks on arrival and then shortly after storage at two dairy processors in California’s San Joaquin Valley during the spring, summer, and fall.