Journal of Animal Science, Vol 71, Issue 2 415-419, Copyright © 1993 by American Society of Animal Science

JOURNAL ARTICLE

Measurement of zeranol in plasma from three blood vessels in steers implanted with zeranol

A. E. Pusateri and D. C. Kenison
Pitman-Moore, Kansas City, KS 66103-1438.

Zeranol (Z) is a widely used growth promotant; however, plasma Z profiles in cattle implanted with Z have not been characterized. This study was conducted to determine bovine plasma Z profiles. In Exp. 1, four steers (BW = 284.8 +/- 5.6 kg) were implanted with 108 mg of Z (Ralgro). To determine the effect of sampling site on plasma Z concentrations, blood was sampled by venipuncture from the maxillary vein ipsilateral (IMV) to the ear in which Z was implanted and from the ipsilateral (IJV) and contralateral (CJV) jugular veins of each steer. Samples were collected on d 1, 4, 6, 8, 11, and 13 after implantation and Z was assayed by RIA. There was an effect of sampling site (P < .01). The overall mean plasma Z concentrations and 95% confidence intervals (CI) for each vessel were 282 (CI: 172 to 463), 135 (CI: 85 to 215), and 67 (CI: 42 to 106) pg/mL for the IMV, IJV, and CJV, respectively. Plasma Z concentration was higher (P < .05) in IMV than in IJV and higher (P < .05) in IJV than in CJV. In Exp. 2, nine steers (BW = 316.7 +/- 10.0 kg) were implanted with 108 mg of Z and IMV blood was collected on d 0, 1, 3, 7, 10, 14, 17, 21, 28, 35, 42, 56, 63, 73, and 91 after implantation. Day affected plasma Z concentration (P < .01); plasma Z was elevated above preimplantation levels for 91 d (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)