Machin Jacob, Brewer Kimberly, Morales-Briceno Abelardo, Fenger Clara, Maylin George, Tobin Thomas
Department of Toxicology and Cancer Biology and the Maxwell H. Gluck Equine Research Center, Dept. of Veterinary Science, University of Kentucky, Lexington, KY, 40546, USA.
, 15775 Cypress Creek Lane, Wellington, FL, 33414, New Zealand.
Ir Vet J. 2022 May 14;75(1):11. doi: 10.1186/s13620-022-00215-8.
Zilpaterol is a β2-adrenergic agonist medication approved in certain countries as a cattle feed additive to improve carcass quality. Trace amounts of Zilpaterol can transfer to horse feed, yielding equine urinary "identifications" of Zilpaterol. These "identifications" occur because Zilpaterol is highly bioavailable in horses, resistant to biotransformation and excreted as unchanged Zilpaterol in urine, where it has a 5 day or so terminal half-life.In horses, urinary steady-state concentrations are reached 25 days (5 half-lives) after exposure to contaminated feed. Zilpaterol readily presents in horse urine, yielding clusters of feed related Zilpaterol identifications in racehorses. The first cluster, April 2013, involved 48 racehorses in California; the second cluster, July 2013, involved 15 to 80 racehorses in Hong Kong. The third cluster, March 2019, involved 24 racehorses in Mauritius; this cluster traced to South African feedstuffs, triggering an alert concerning possible Zilpaterol feed contamination in South African racing. The fourth cluster, September/October 2020 involved 18 or so identifications in French racing, reported by the French Laboratories des Courses Hippiques, (LCH), and in July 2021, a fifth cluster of 10 Zilpaterol identifications in South Africa.The regulatory approach to these identifications has been to alert horsemen and feed companies and penalties against horsemen are generally not implemented. Additionally, given their minimal exposure to Zilpaterol, there is little likelihood of Zilpaterol effects on racing performance or adverse health effects for exposed horses.The driving factor in these events is that Zilpaterol is dissolved in molasses for incorporation into cattle feed. Inadvertent incorporation of Zilpaterol containing molasses into horse feed was the source of the California and Hong Kong Zilpaterol identifications. A second factor in the 2019 Mauritius and 2020 French identifications was the sensitivity of testing for Zilpaterol in Mauritius and France, with the French laboratory reportedly testing at a "more sensitive level for Zilpaterol". As of January 1, 2021, the new FEI Atypical Finding (ATF) policy specifies Zilpaterol as a substance to be treated as an Atypical Finding (ATF), allowing consideration of inadvertent feed contamination in the regulatory evaluation of Zilpaterol identifications.
齐帕特罗是一种β2 - 肾上腺素能激动剂药物，在某些国家被批准用作牛饲料添加剂以改善胴体品质。痕量的齐帕特罗会转移到马饲料中，导致马尿中出现齐帕特罗的“检测阳性”。出现这些“检测阳性”是因为齐帕特罗在马体内具有很高的生物利用度，抗生物转化，并以未改变的齐帕特罗形式经尿液排出，其在尿液中的终末半衰期约为5天。在马体内，接触受污染饲料25天（5个半衰期）后达到尿液稳态浓度。齐帕特罗很容易出现在马尿中，导致赛马中出现与饲料相关的齐帕特罗检测阳性群。第一起检测阳性群事件发生在2013年4月，涉及加利福尼亚州的48匹赛马；第二起发生在2013年7月，涉及香港的15至80匹赛马。第三起发生在2019年3月，涉及毛里求斯的24匹赛马；该事件追溯到南非饲料，引发了对南非赛马中可能存在齐帕特罗饲料污染的警报。第四起发生在2020年9月/10月，法国赛马实验室（LCH）报告法国赛马中有18起左右的检测阳性；2021年7月，南非出现了第五起包含10起齐帕特罗检测阳性的事件。针对这些检测阳性的监管措施是向骑手和饲料公司发出警报，一般不对骑手实施处罚。此外，鉴于马匹对齐帕特罗的接触极少，齐帕特罗对参赛表现或受影响马匹的健康产生不良影响的可能性很小。这些事件的驱动因素是齐帕特罗溶解在糖蜜中用于掺入牛饲料。含有齐帕特罗的糖蜜意外掺入马饲料是加利福尼亚州和香港出现齐帕特罗检测阳性的源头。2019年毛里求斯和2020年法国检测阳性事件的另一个因素是毛里求斯和法国对齐帕特罗检测的敏感性，据报道法国实验室对齐帕特罗的检测“更敏感”。截至2021年1月1日，国际马联新的异常发现（ATF）政策将齐帕特罗指定为一种应被视为异常发现（ATF）的物质，在对齐帕特罗检测阳性的监管评估中允许考虑意外的饲料污染情况。
