Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 5, 2009
Publication Date: September 7, 2009
Citation: Shelver, W.L., Thorson, J., Hammer, C., Smith, D.J. 2009. Determination of Zilpaterol in Horse Urine from Withdrawal Day 0 to Day 21 by UPLC-MS/MS and ELISA. In: Proceedings of Xth International Conference on Agri-Food Antibodies (ICAFA), September 7-10, 2009, Wageningen, The Netherlands. Presentation L-15, page 24. Technical Abstract: Zilpaterol is a beta-adrenergic agonist that is approved in the United States, Mexico and South Africa as a feed additive to increase weight gain and improve feed efficiency of cattle. Beta-adrenergic agonists have a long history of illicit and off-label use in livestock, competitive sport animals, and in human athletes and a great potential for off-label use continues. Gaining an understanding of the rates of zilpaterol depletion from target and non-target animals is important in developing effective strategies for detection of inappropriate zilpaterol use. To this end, zilpaterol was fed to three horses (160 µg/kg body weight) on study day 0 and to two horses at 43 µg/kg bw on study day 1. Urine samples were collected from study day 0 through study day 21. Urinary zilpaterol concentrations were measured by ultra performance liquid chromatography-triple quadruple tandem mass spectrometry with a matrix match external standard as well as by enzyme linked immunosorbant assay. Based on the LC-MS/MS results, the urine concentration ranged from 10,400 µg/L on withdrawal day 0 to 0.5 µg/L on withdrawal day 21. Both methods were sensitive enough to measure urinary zilpaterol to withdrawal day 21. The mass spectral and immunochemical methods were highly correlated having an r2 of 0.94. Because of its simplicity, cost-effectiveness, and rapidity, ELISA is a convenient method for determining zilpaterol levels in urine without requiring extensive cleanup procedures.