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Veterinarians play an essential role in the prevention of doping in equine sports, both as attending clinicians as well as official competition veterinarians. This complex task requires comprehensive knowledge concerning the pertinent regulations. These include official laws, such as the animal protection and medicines laws as as well as rules issued by the responsible equine sports authority. Furthermore, veterinarians are required to determine adequate withdrawal times following the legitimate use of medications in sport horses. This may be performed by applying appropriate data published by the respective equestrian sports authorities. In case such data is not available, pharmacokinetic heuristics elucidated in this article may be utilized in order to define suitable withdrawal times. Furthermore, veterinarians are recommended to advise horse owners concerning the risk of feed contaminants that may cause inadvertent positive anti-doping samples. In this context, the prevention of botanical contaminations in roughage is of importance in central Europe. Official veterinarians fulfil the task of anti-doping sampling during competitions. In order to guarantee a correct procedure, precautions for the avoidance of sample contamination are warranted and correct identification of the samples must be ensured. These procedures are described by means of the rules of the German Equestrian Federation., Competing Interests: Der Autor bestätigt, dass kein Interessenkonflikt besteht., (© Georg Thieme Verlag KG Stuttgart · New York.)

Based on their performance-enhancing potential, caffeine and theophylline are prohibited substances in equine sports. Residues in horses can be caused by wilful application or by unintended uptake of contaminated feed. The International Federation of Horseracing Authorities recently introduced international residue limits (IRLs) to facilitate the discrimination between pharmacological relevant and irrelevant concentrations in doping samples. The objective of this study was to investigate the scientific validity of these IRLs. A systematic analysis was performed to assess the IRLs by different statistical approaches using published pharmacokinetic data. 31 out of 218 potentially relevant publications met the inclusion criteria. Thereby, both IRLs were found to be appropriate for the exclusion of the presence of a relevant pharmacological effect after a wilful application. The IRL of theophylline was also determined to be suitable for the prevention of positive doping tests caused by the ingestion of contaminated feed. In contrast, the IRL of caffeine is not suitable to prevent positive doping test caused by the ingestion of more than 10 mg caffeine per day per horse with contaminated feed. The lack of corresponding regulation for paraxanthine, a major active metabolite of caffeine and theophylline, was recognised as a substantial shortcoming of the current system, rendering both IRLs incomplete., Competing Interests: Competing interests: None declared., (© British Veterinary Association 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Pyrrolizidine alkaloids are secondary plant metabolites with hepatotoxic effect in humans and several animal species. In recent studies, foods such as herbal teas and honey have been found to be contaminated with pyrrolizidine alkaloids., Objectives: The aim of this study was to identify and assess pyrrolizidine alkaloids in compound feeds manufactured for horses and containing either alfalfa or a blend of herbs., Methods: Forty-eight feed products for horses were included in the study. The feedstuffs were analysed for 28 selected pyrrolizidine alkaloids by liquid chromatography-mass spectrometry. The concentrations of the individual pyrrolizidine alkaloids were summed to calculate the total pyrrolizidine alkaloid content., Results: In 7 of 48 samples, pyrrolizidine alkaloid concentrations were below the limit of quantification of 1-5 μg/kg. The median of 41 out of 48 samples was 58 μg/kg, and the 25 and 75th percentiles were 8 and 151 μg/kg. The highest observed pyrrolizidine alkaloid concentrations, 1306 and 1222 μg/kg, were found in two alfalfa-based feed products, followed by 836 μg/kg in an herb-containing feed product. Lycopsamine, seneciphylline, seneciphylline-N-oxide, senecionine and senecionine-N-oxide were the most frequently detected alkaloids., Main Limitations: Risk assessment was based on no-observed-adverse-effect-level for pyrrolizidine alkaloids in rats and humans. The specific susceptibility of horses to pyrrolizidine alkaloids remains unknown., Conclusions: According to our risk assessment, pyrrolizidine alkaloid contamination should be limited to <90 μg/kg in equine compound feeds. We showed a high rate of pyrrolizidine alkaloids contamination in feed products for horses. In 43% of the analysed samples, pyrrolizidine alkaloid levels exceeded the calculated maximum tolerable levels. There is a need to introduce measures to reduce pyrrolizidine contamination in equine feedstuffs. The Summary is available in Portuguese - see Supporting Information., (© 2018 EVJ Ltd.)

Opioid alkaloids were identified in the urine of horses during an anti-doping control and in a case of intoxication. In both cases, it was suspected that the horses had ingested poppy-contaminated feed. To verify this suspicion, possible opioid alkaloid sources in Germany were identified through a literature research. Additionally, the contaminated feed was botanically and chemically analysed. The results indicated that both cases were most probably caused by the poppy in the feed. This highlights the previously underestimated risk of an intake of poppy-contaminated feed in horses. Recommendations are formulated for the prevention of positive doping-test results and intoxications by poppy-contaminated feeds in horses. Furthermore, a threshold for morphine in urine samples in competing horses is proposed.