The use of hair as a long-term indicator of low-dose β2 agonist treatments in cattle: Implications for growth-promoting purposes monitoring

Ractopamine (RAC), a β-adrenergic leanness-enhancing agent, endangers the food safety of animal products because of overdosing and illegal use in food animals. Excretion and residue depletion of RAC in pigs and goats were investigated to determine a representative biological fluid or surface tissue for preslaughter monitoring. After a single oral gavage of RAC, 64-67% of the dose was excreted from the urine of pigs and goats within 12-24 h. RAC persisted the longest in the hair of pigs and goats but depleted rapidly in the plasma, muscle, and fat. Urine and hair were excellent for predicting RAC residues in edible tissues of pigs, whereas plasma and urine were satisfactory body fluids for the prediction of RAC concentrations in edible tissues of goats. These data provided a simple and economical preslaughter living monitoring method for the illegal use and violative residue of RAC in food animals.

Clenbuterol is a well-established β2-agonist, which is prohibited in sports and strictly regulated for use in the livestock industry. During the last few years clenbuterol-positive results in doping controls and in samples from residents or travellers from a high-risk country were suspected to be related the illegal use of clenbuterol for fattening. A sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to detect low clenbuterol residues in hair with a detection limit of 0.02 pg/mg. A sub-therapeutic application study and a field study with volunteers, who have a high risk of contamination, were performed. For the application study, a total dosage of 30 µg clenbuterol was applied to 20 healthy volunteers on 5 subsequent days. One month after the beginning of the application, clenbuterol was detected in the proximal hair segment (0-1 cm) in concentrations between 0.43 and 4.76 pg/mg. For the second part, samples of 66 Mexican soccer players were analyzed. In 89% of these volunteers, clenbuterol was detectable in their hair at concentrations between 0.02 and 1.90 pg/mg. A comparison of both parts showed no statistical difference between sub-therapeutic application and contamination. In contrast, discrimination to a typical abuse of clenbuterol is apparently possible. Due to these findings results of real doping control samples can be evaluated.