Anti-Zilpaterol monoclonal antibody

Establishment of an analytical method on zilpaterol (ZPT), the beta-agonists, and a growth promoting agent for livestock was undertaken. Analytical method for ZPT in the beef by LC-ESI-MS/MS was adopted. Before sample extraction, a beef sample was hydrolyzed by beta-glucuronidase/arylsulfatase and 0.2 M ammonium acetate buffer solution. Afterwards, the mixture was extracted with ethylacetate and then defatted by n-hexane/methanol partitioning. Subsequently, the separated organic layer was evaporated and the dissolved solution was purified by using a Molecular Imprinted Polymer solid phase extraction. The quantitation was carried out using LC-ESI-MS/MS with C, a non-polarity column under the gradient condition with 10 mM ammonium acetate (pH 4.3) : acetonitrile (95 : 5 (v/v), a mobile phase A) and acetonitrile (a mobile phase B). The standard calibration curve presented linearity of correlation coefficient (r(2)) > 0.999, analyzed from 0.2 to 10 ng/mL. The limit of quantitation in a beef showed 0.2 mu g/kg. The average recoveries of intra- and inter-day experiment ranged from 100.9 to 108.5% and 103.3 to 104.5%, respectively. The repeatability and reproducibility for intra- and inter-day measurement expressed as a relative standard deviation was less than 10.0%, respectively. Therefore, the established analytical method for ZPT residue in beef was applicable to the official analytical method with the acceptable level of sensitivity, repeatability and reproducibility.

British and British x Continental steers (n = 560; initial BW = 339.4 +/- 1.76 kg) were used in a serial slaughter study with a completely random design to evaluate effects of zilpaterol hydrochloride (ZH; 8.33 mg/kg of dietary DM basis) on performance and carcass characteristics. Treatments were arranged in a 4 x 4 factorial (112 pens; 7 pens/treatment; 5 steers/pen) and included duration of ZH feeding (0, 20, 30, or 40 d before slaughter plus a 3-d ZH withdrawal period) and days on feed (DOF) before slaughter (136, 157, 177, and 198 d). No duration of ZH feeding x slaughter group interactions were detected for the performance measurements (P > 0.10). Final BW did not differ (P = 0.15) between the 0-d group and the average of the 3 ZH groups, but ADG was greater for the average of the 3 ZH groups during the period in which ZH diets were fed (P < 0.01) and for the overall feeding period (P = 0.05). As duration of ZH feeding increased, DMI decreased (P = 0.01) and G: F increased linearly (P < 0.01). With the exception of KPH (P = 0.022), no duration of ZH feeding x slaughter group interactions (P > 0.10) were detected for carcass characteristics. Regardless of the duration of ZH feeding, cattle fed ZH had greater HCW (P < 0.01), greater dressing percent (P < 0.01), less 12th-rib fat (P < 0.01), larger LM area (P < 0.01), less KPH (P = 0.03), and lower yield grade (P < 0.01) than the 0-d cattle. The 0-d group had greater marbling scores (P < 0.01) than cattle fed ZH diets, with a tendency for a linear decrease in marbling score (P = 0.10) as duration of ZH feeding was extended. A greater percentage of carcasses in the 0-d group graded USDA Choice or greater (P < 0.01) than in the 3 ZH groups, whereas the percentage of Select carcasses was greater (P = 0.01) for the 3 ZH groups. From d 0 to end (P = 0.04) and during the last 43 d on feed (P < 0.01), ADG responded quadratically to DOF before slaughter. No differences were detected among slaughter groups for DMI for the entire trial period; however, a quadratic response (P = 0.02) was observed for the final 43 d before slaughter. A quadratic response was also detected for the final 43 d before slaughter (P < 0.01) and from d 0 to end (P = 0.02) for G: F. Final BW, HCW, dressing percent, and 12th-rib fat increased linearly (P < 0.01) as DOF before slaughter increased. Our results indicate that no substantial effects on performance and carcass measurements were observed when ZH was fed for 30 or 40 d as opposed to 20 d, and that effects of ZH generally did not interact with DOF before slaughter.