Accumulation of clenbuterol residues in the hair of Chinese Simmental beef cattle during and after treatment.

The aim of this study was to evaluate the concentrations of clenbuterol residues in the red hair of Chinese Simmental beef cattle following exposure to two doses of clenbuterol for 21 days. This experiment was conducted in six male red pied Chinese Simmental beef cattle which were randomly divided into two groups (n = 3). Groups 1 and 2 were administered clenbuterol at a dose of 16 and 48 μg/kg body weight (BW)/day, respectively. Hair samples were collected on Days 7, 14 and 21 during treatment, and on Days 0, 14, 28, 42 and 70 after discontinuation of medication, using liquid chromatography tandem mass spectrometry (LC-MS-MS) method. About 500 mg hair samples spiked with 50 pg/mg D9-clenbuterol internal standard were analyzed with which the method recovery was from 88.6 to 116.9%. The results showed that clenbuterol was significantly accumulated in hair, with a concentration of 0.98 ± 0.56 pg/mg in Group 1 and 6.34 ± 3.21 pg/mg in Group 2 on Day 7 of treatment, and the residue concentrations increased as treatment proceeded. During the early withdrawal period, the residues increased from 13.52 ± 8.69 to 17.96 ± 6.94 pg/mg in Group 1 and from 55.15 ± 4.04 to 147.79 ± 15.35 pg/mg in Group 2. No significant differences were found in the later withdrawal period in both treatment groups. The results of the present study indicated that the red hair of Chinese Simmental beef cattle has high accumulation potential for clenbuterol residues. Hair, as a target matrix, even light-pigmented hair, can be used to monitor clenbuterol abuse over a long period.