Toward a New European Threshold to Discriminate Illegally Administered from Naturally Occurring Thiouracil in Livestock

Abstract

Thiouracil is a thyrostat inhibiting the thyroid function, resulting in fraudulent weight gain if applied in the fattening of livestock. The latter abuse is strictly forbidden and monitored in the European Union. Recently, endogenous sources of thiouracil were identified after frequently monitoring low-level thiouracil positive urine samples and a "recommend concentration" (RC) of 10 μg/L was suggested by the EURL to facilitate decision-making. However, the systematic occurrence of urine samples exceeding the RC led to demands for international surveys defining an epidemiologic threshold. Therefore, six European member states (France, Poland, The Netherlands, United Kingdom, Norway, and Belgium) have shared their official thiouracil data (2010-2012) collected from bovines, porcines, and small livestock with 95 and 99% percentiles of 8.1 and 18.2 μg/L for bovines (n = 3894); 7.4 and 13.5 μg/L for porcines (n = 654); and 7.4 μg/L (95% only) for small livestock (n = 85), respectively. Bovine percentiles decreased with the animal age (nonadults had significantly higher levels for bovines), and higher levels were observed in male bovines compared to female bovines.

Mass spectrometric method for distinguishing isomers of dexamethasone via fragment mass ratio: An HRMS approach

“…Even though, there is no justification for their use in sports. An athlete adopting any of these substances or methods, during sports will result in disqualification and face legal proceedings …”

“…An athlete adopting any of these substances Abbreviations: % RA, Percentage mass relative abundance; CE, Collision energy; DIA, Data independent acquisition; HCD, Higher-energy collisional dissociation; HESI, Heated electrospray ionization; HPLC, High performance liquid chromatography; HRMS, High-resolution accurate mass spectrometer; IFHA, International federation of horseracing authorities; LCMS, Liquid chromatography mass spectrometer; RA, Mass relative abundance; UHPLC, Ultrahigh performance liquid chromatography or methods, during sports will result in disqualification and face legal proceedings. 19,20 Dexamethasone, 21-23 betamethasone, 4,24,25 and paramethasone 26,27 are synthetic glucocorticosteroids authorized for therapeutic use in equine and is controlled by a threshold limits in urine and plasma by International federation of horseracing authorities (IFHA) (Figure 1).…”

Discovery of urinary biomarkers to discriminate between exogenous and semi-endogenous thiouracil in cattle: A parallel-like randomized design

“…This resulted in a constant monitoring by the European Union member states in order to discourage thyreostat abuse, being at risk of severe penalties. In this context, it may be noted that administration of thyreostats has become rather uncommon because of the fast elimination kinetics and inefficient growth-promoting actions [ 4 , 5 ]. As such, the use of growth promotors at very low doses in combination with other drugs, aiming at additional or synergistic effects, has become more popular in the last decade [ 6 , 7 ].…”

Determination of Thyreostats in Bovine Urine and Thyroid Glands by HPLC–MS/MS

“…The Community Reference Laboratories (CRLs) in 2007 proposed a recommended concentration of 10 μg L −1 in urine and 10 μg kg −1 in thyroid tissue for the purpose of control, as "low concentrations of thiouracil have been detected in bovine animals fed with cruciferous plants, however, there is scientific evidence showing that levels above 10 ppb in urine cannot be linked to natural origin due to this contamination" [17]. Recently, Wauters et al reported concentrations of up to 18.2 μg L −1 in the 99 % percentile from 3894 bovines and they suggested that the recommended concentration should be increased to 30 μg L −1 [18]. In fact, the 2015 Italian National Residue Plan already provides this concentration as the limit of detection for thyreostats in urine [19].…”