Hardly a week goes by without the U.S. Food and Drug Administration (FDA) handing out an official warning to an American dairy farmer about the overdose of antibiotics in animals.

But with 55,000 American dairy farms and a U.S. dairy herd numbering more than 9 million cows, how significant are those weekly warnings?

Now a study from across the pond may shed some light on this topic.

The independent Veterinary Residues Committee (VRC) in the United Kingdom over the weekend announced findings on more than 34,000 samples taken from animals in 2009.

“The results of the surveillance in the UK show that the great majority of our farmers are using veterinary medicines responsibly,” said Dorothy Craig, who chairs the VRC.

“Where the instructions on the use of a medicine were observed, including the withdrawal period, any residues detected were within agreed limits,” Craig added. “We still detected some residues of concern, which underlines the need for all involved in the livestock industry to follow best practice in using medicines.”

In its ninth annual report, VRC provided results on 34,000 domestic and 1,300 imported samples that were subjected to testing for veterinary medicines and other substances.

Food safety agencies, like FDA in the U.S. and the Food Standards Agency in the UK, set limits or maximum tolerances for substances such as antibiotics in the edible tissues of animals sold for slaughter for human consumption.  These limits are set, in part, to prevent people from building up tolerances to antibiotics, and thereby make them ineffective for treating infections like those from foodborne illnesses.

In the sampling, the VRC found only three substances that are banned from human consumption.

Phenylbutazone, an anti-inflammatory drug used to treat horses, was found in cattle samples from two different farms in Northern Ireland.  Chloramphenicol, which is use in eye drops, was found in farmed golden thread bream imported from Vietnam.  And, furazolidone, a nitrofuran antibiotic, was found in a sample of black tiger prawns from India.

Long-term exposure to nitrofuran antibiotics is associated with increased cancer risk.  Phenylbutazone and Chloramphenicol are banned because they can in rare cases cause serious and potentially fatal blood disorder and aplastic anemia.

Some examples of where VRC sampling found residues above the limits included:

-1,600 samples of broiler livers found 48 with concentrations high than allowed levels of one of five different animal antibacterial drugs.

-1,100 samples of cattle kidneys found only one with levels of Tilmicosin, an antibiotic.

-200 calf kidneys found two with higher than allowed limits of the animal drug Chlortetracycline and two with Dihydrostreptomycin over the limit.

-Urine of 1,800 cattle was tested and 23 exceeded steroid screen levels.

-1,300 pig kidneys returned only four with levels of antimicrobials that exceeded the limits.

The complete findings can be found in the VRC Annual Report, which will be the subject of a public meeting in York on Oct. 13.

Dairy farms are generally smaller in the Britain than in the U.S., although an 8,100 head dairy in the permitting stage is now generating controversy throughout the UK.  About 90 percent of U.S. dairies milk 200 or fewer cows.