|CHAKRABARTY, SHUBHASHIS - Orise Fellow|
|HOFFMAN, TRAVIS - North Dakota State University|
Submitted to: Food Additives & Contaminants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2019
Publication Date: 6/20/2019
Citation: Smith, D.J., Shelver, W.L., Chakrabarty, S., Hoffman, T.W. 2019. Detection and quantification of residues in sheep exposed to trace levels of dietary zilpaterol HCl. Food Additives & Contaminants: Part A. 36(9):1289-1301. https://doi.org/10.1080/19440049.2019.1627005.
Interpretive Summary: Zilpaterol is a livestock feed additive that is approved for use in cattle in the United States, Canada, and several other countries. Nevertheless, many US trade partners, competitive sports organizations (animal and human), and livestock trade shows strictly prohibit zilpaterol use. The presence of zilpaterol in food animals other than cattle is strictly proscribed. Modern analytical methods are so sensitive, however, that even accidental, trace-level zilpaterol exposures might cause positive test results. This study was conducted to determine what levels of dietary zilpaterol would cause positive test results in urine and tissues of exposed sheep using a variety of commonly used analytical methods. We clearly demonstrated that sheep given amounts ranging from one-thousandth to one-tenth the normal dose could be identified using a variety of modern analytical tools. The data clearly demonstrated that animals exposed to the equivalent of trace-level zilpaterol contamination would likely test positive using a variety of common analytical methods.
Technical Abstract: Urine and tissues from sheep fed trace-levels of dietary zilpaterol were tested using common and novel screening and quantitative analytical methods. Sheep (50.0 ± 2.7 kg) were offered feed (1.75 kg) containing 0.0075 (L), 0.075 (M), or 0.75 (H) mg/kg of zilpaterol for 12 days and were slaughtered with 0-day (L-0, M-0, H-0; n = 4 each) or 3-day (H-3; n = 4) withdrawal periods. Rapid immunochromatographic assays (ICA) consistently detected urinary zilpaterol (LOD = 1.7 ng/mL) in L-0 (54.2%), M-0 (96.0%), and the H-0 (100%) treatment groups but only detected zilpaterol in tissues (LOD ~2.4 ng/g) from the H-0 group. Advanced MS-based technologies detected zilpaterol in some, but not all, tissues of M0, H0, L-0, and H-3 sheep. Analytical techniques commonly used to ensure compliance with show-animal rules, import/export guidelines, and regulatory statutes routinely detected residues in animals exposed to zilpaterol at doses insufficient to elicit growth responses.