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FDA warning letters reveal antibiotic epidemic in America's dairies

Cattle at factory-like dairy farms are often given rBST, which can increase their odds of mastitis, leading to antibiotic dosing.
Cattle at factory-like dairy farms are often given rBST, which can increase their odds of mastitis, leading to antibiotic dosing.Photo by Bruno Vincent/Getty Images

Hundreds of warning letters issued by FDA over the course of the past fourteen years cite America's dairy farmers for "illegal drug residue." The drug in question, all too often, is gentamicin, an antibiotic whose overuse is linked to the development of antibiotic-resistant bacteria. Although FDA flags cattle sold for consumption as containing gentamicin, a drug for which a safe level has not been established, these cattle originate on dairy farms, indicating that they were used -- or overused -- for milk production before being sold as food. One reason behind this epidemic of antibiotic use may be the prevalence of Posilac, a recombinant bovine growth hormone created by Monsanto and now marketed by Eli Lilly to increase milk production among dairy cows.

The most recent letter, issued to Griffith Dairy on April 22, is typical: "We found that you offered for sale an animal for slaughter as food that was adulterated. [...] USDA / FSIS analysis of tissue samples collected from this animal identified the presence of gentamicin in the kidney tissue. [...] Our investigation also found that you hold animals under conditions that are so inadequate that medicated animals bearing potentially harmful drug residues are likely to enter the food supply." Additional details of the citation reveal that Griffith Dairy does not maintain records of medicated animals, that the drugs given to the cattle are adulterated, and that antibiotics are given to dairy cattle without the supervision of a veterinarian.

Approved for use in dairy cattle in November 1993 for the purpose of increasing the duration of lactation, Posilac (also known as rBST or rBGH) is most popular among large dairy owners. The average national adoption rate was 15.2 percent in 2007, but data from Wisconsin, a large dairy state, show that the adoption rate increases with the size of the dairy. For example, in 1999, nearly 35 percent of dairies with 100 to 199 cows used rBST, and an astounding 75 percent of dairies with 200 or more cows used the drug.

The warning label for Posilac clearly states that mastitis is a known side effect of the product: "Cows injected with Posilac are at an increased risk for mastitis (visibly abnormal milk) and may have higher somatic cell counts. [...] Cows injected with Posilac may require more therapeutic drug treatment for mastitis and other health problems." Despite these warnings, the USDA does not require a milk discard period or preslaughter withdrawal period for the drug, a factor that may underlie the rash of antibiotic adulteration of dairy cattle sold for meat after their milk-producing days end. Although FDA requires a withdrawal period for antibiotics given to animals that will enter the food chain, the agency's own warning letters provide ample proof that withdrawal periods are frequently neither observed nor documented.

An OIG report from April 2010 reveals that "FDA inspects less than a quarter of food facilities each year, and the number of facilities inspected has declined over time." Perhaps more disturbing, OIG reports that "the number of inspections of facilities that have been designated by FDA as 'high risk' has also declined." In fact, 56 percent of food facilities have gone at least five years without an FDA inspection. Given these data, it is likely that both meat and milk from dairies using rBST have a higher incidence of antibiotic contamination than the public -- or FDA -- knows. It is also likely that at least some antibiotic-contaminated meat and milk regularly enter America's food supply.