In 2010, 34.5 million head of cattle (of all classes) were slaughtered in the U.S. According to the Food Safety and Inspection Service’s (FSIS) United States National Residue Program for Meat, Poultry, and Egg Products 2010 Residue Sample Results report (, an interagency chemical testing program administered by FSIS examined food samples for the presence of 128 chemical compounds, including 78 veterinary drugs, 45 pesticides, and 5 environmental contaminants.

The majority of violations detected by the 2010 domestic scheduled sampling plan were veterinary drugs, particularly sulfonamides and antibiotics used to prevent or treat bacterial infections. Generally, drug residue violations result from an inadequate withdrawal time for the drugs to clear the animal’s system. Detected residues are usually concentrated in kidney and liver tissue rather than in muscle tissue. Of the 211,733 samples analyzed in 2010, there were 1,632 violations: 23 from scheduled sampling and 1,609 from the inspector-generated program.

Out of 211,733 samples, FSIS labs reported 2,043 residue violations in 1,609 animals (a single animal may have multiple violations). Of those, bovines accounted for: beef cows (84), bob veal (765), bulls (8), dairy cows (700), formula fed veal (3), heavy calves (5), heifers (10), non-formula fed veal (7) and steers (23). Neomycin accounted for the most residue violations across the inspector-generated program (520 or 25%), followed by flunixin (285 or 14%) and penicillin (281 or 14%).

It is important to recognize that the tolerances set for drugs, i.e., the level of drug found in edible tissues above which residues are violative, are now being interpreted by the FSIS to only apply to the production class of animal for which the drug was approved. For example, if a drug is used in a veal calf, and the drug was not approved for veal calves and only for beef cattle, the established tolerance only applies in beef animals and not in veal. The result is that any detectable amount could result in the FSIS calling the sample violative. The production classes of cattle are beef, dairy, and veal.

Besides the 2,043 residue violations, there were 4,215 samples reported as non-violative positives. Again, neomycin accounted for the highest percentage of non-violative positive samples (1,884 or 45%), followed by dihydrostreptomycin (487 or 12%) and tetracycline (516 or 12%). Bob veal, dairy cows, and beef cows had the highest number of positive nonviolative results.

FSIS publishes a weekly Residue Repeat Violator List ( that lists, by state, operations that have had repeat violations on a rolling 12-month basis, what class of animal was involved, what tissue was sampled and what drug was identified.