According to an article in The Washington Post, a study recently published in Science of 699 cattle in the USDA's 'no antibiotics' labeling program found that some of them tested positive for antibiotics.
The USDA says it will be interested to review the results, though confidentiality agreements might prevent identifying the specific feed lots involved.
Cattle certified as free of antibiotics command higher prices at all levels of the distribution chain, from ranchers to retail stores.