Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/31/2010
Publication Date: 5/1/2010
Citation: Schneider, M.J., Mastovska, K., Solomon, M.B. 2010. Distribution of Penicillin G Residues in Culled Dairy Cow Muscles: Implications for Residue Monitoring. Journal of Agricultural Food & Chemistry. 58(12):5408-5413. Interpretive Summary: Antibiotics and other veterinary drugs are used by veterinarians to treat disease and improve animal health. To ensure the safety of the food supply, the federal government establishes drug residue tolerance levels for edible animal tissues, These tolerances are often set for muscle, but no specific muscle type is targeted for monitoring. The purpose of this study was to determine if drug residue levels would depend on muscle type, and whether muscle juice, a matrix that is easier to work with, could serve as a substitute for muscle in the analysis. In this work, culled dairy cattle were dosed with Penicillin G (Pen G) and sacrificed 1, 2, or 5 days after withdrawal from the drug. A variety of muscle samples were collected from each animal, as well as liver and kidney samples. Extracts of all samples were analyzed for Pen G. Results showed that Pen G residue levels can vary between and within different muscles. Muscle juice appeared to be a promising substitute for muscle as a matrix for preliminary analysis. Due to the potential for variation within muscles, all samples taken need to be large enough so as to be representative. These findings are helpful to regulatory agencies as they determine what tissues are sampled for their monitoring programs to ensure the established residue safety tolerance levels are not exceeded.
Technical Abstract: The U.S. Food and Drug Administration sets tolerances for veterinary drug residues in muscle, but does not specify which type of muscle should be analyzed. In order to determine if antibiotic residue levels are dependent on muscle type, 7 culled dairy cows were dosed with Penicillin G (Pen G) from 1-3 days and then sacrificed on day 1, 2 or 5 of withdrawal. A variety (9-15) of muscle samples were collected, along with liver and kidney samples. In addition, corresponding muscle juice samples were prepared. All samples were extracted and analyzed by LC-MS/MS to determine Pen G levels. Results showed that Pen G residue levels can vary between and within different muscles, although no reproducible pattern was identified between cows or withdrawal times. Muscle juice appeared to be a promising substitute for muscle as a matrix for screening purposes. Due to the potential for variation within muscles, all samples taken need to be large enough so as to be representative.