Antibiotic Residues in Cattle Reported to Be Raised Without Antibiotics

In 2019, the U.S. Department of Agriculture’s (USDA) Food Safety and Inspection Service (FSIS) provided revised guidance for labeling claims of “raised without antibiotics” (RWA) and similar terms for meat and poultry produced in the US. In 2022, Price et al. published a study reporting that 15% of RWA-labeled cattle contained antibiotic residues in urine samples. In 2023, the USDA embarked on the project reported herein to independently determine the extent of antibiotic drug residues present in kidney and liver tissues from slaughtered cattle purported to be RWA. In this study, FSIS inspectors randomly collected kidney and liver tissues from 189 RWA animals in 79 slaughter establishments across the US. The samples were monitored for 185 veterinary drugs multiple times by different means, including liquid-chromatography coupled with tandem mass spectrometry (LC-MS/MS) and quadrupole high-resolution MS with an orbital ion trap instrument (LC-Q/orbitrap). Samples from 37 animals (20%) met the analytical identification criteria for at least one antibiotic confirmed in at least two analyses. Multiple antibiotics were determined in 11 RWA animals. Macrolides (tulathromycin, tildipirosin, tilmicosin, and gamithromycin) were confirmed in 20 (11%) of the RWA animals. The ionophore, monensin, was also confirmed in tissues from 11 samples, with unconfirmed/partial identifications in 8 others. Tetracyclines were confirmed in samples from 12 animals, several of which were found to contain multiple antibiotic residues. One animal each was also found to be positive for sulfamethazine (a sulfonamide antibiotic) and metabolites of penicillin G (a β-lactam antibiotic). Although they are not antibiotics, two anthelmintics (fenbendazole and eprinomectin) were confirmed in tissues from 3 RWA animals. FSIS has informed the slaughter establishments with positive results and advised them to conduct a root cause analysis and implement corrective actions.