Residues of Ractopamine and Identification of its Glucuronide Metabolites in Plasma, Urine, and Tissues of Cattle

Abstract

Ractopamine was approved by the US Food and Drug Administration for use as a growth promoter on cattle a decade ago is still banned by the European Union and most Asian countries. While, ractopamine residues in living samples and some organs (besides liver, muscle and kidney) of cattle under the recommended feed condition (10-30 mg/kg in dry matter, 28-42 days) remains unclear. In this study, nine cattle (246.22 ± 18.17 kg) were fed 0.67 mg/kg body weight (equivalent to 30 mg/kg in dry matter) of ractopamine for 28 days to investigate the residues of ractopamine in plasma, urine and organs. Plasma and urine were sampled during treatment and withdrawal period. Three cattle were slaughtered on withdrawal days 0 and 3 for organs collection. Ractopamine was determined by LC-MS/MS and its glucuronide metabolites were identified by Q-TOF/MS. Ractopamine concentrations in plasma and urine reached highest on treatment day 14 (2.88 ng/mL) and day 7 (4713.25 ng/mL), respectively. On withdrawal day 28, ractopamine concentrations in plasma and urine and were undetectable (limit of quantitation, 0.2 ng/mL) and 4.21 ng/mL, respectively. On withdrawal day 0, ractopamine residue in tissues were as follows: liver > eye > lung > spleen > aqueous fluid > heart > bile > kidney > gluteus > rib eye muscle. Compared with those on withdrawal day 0, ractopamine contents in most tissues that sampled on withdrawal day 3 were lower (P < 0.05), while that in the eye tissues, aqueous fluid, and kidney were stable or higher. These results provide extensive data for risk management in ractopamine approved countries and monitoring of the illegal usage in countries that ban ractopamine.

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

“…3 Ractopamine residues in plasma and urine were undetectable (LOQ 0.2 ng/mL) by Day 28 of withdrawal after treatment with growth-promoting doses for 28 days. 8 In the current study, residues of the three β 2 agonists were eliminated rapidly in body fluids (being undetectable in plasma after 14 days, whereas in urine, all residues were below or near the LOQ by Day 42 of withdrawal). These results indicate that current body-fluid-based monitoring strategies might be inadequate when it comes to testing residues of combinations of low-dose β 2 agonists.…”

“…Residue concentrations in cattle treated with growth‐promoting doses of the β 2 agonist clenbuterol for 21 days, on or after Day 14 of withdrawal, were lower than the LOD (0.06 ng/mL) and residues in urine were lower than LOD (0.16 ng/mL) 42 days after treatment; for salbutamol, residues in plasma were below LOQ (0.2 ng/mL) by Day 7 of withdrawal and were near to LOQ in urine on Day 28 of withdrawal . Ractopamine residues in plasma and urine were undetectable (LOQ 0.2 ng/mL) by Day 28 of withdrawal after treatment with growth‐promoting doses for 28 days . In the current study, residues of the three β 2 agonists were eliminated rapidly in body fluids (being undetectable in plasma after 14 days, whereas in urine, all residues were below or near the LOQ by Day 42 of withdrawal).…”

“…The rapid elimination of the three β 2 agonists in plasma and urine observed in this study was similar to that reported elsewhere. 3,6,8,12,17,18 Previous studies reported that total ractopamine in the serum and urine of pigs fed 18 mg/kg of dietary ractopamine for (A)…”

“…However, the illegal use of these compounds continues to be widely reported . Over the past few decades, methods have been developed to monitor the illegal use of these compounds in both humans and animals . It is generally accepted that chemical testing of biological fluids is the most objective approach to diagnose drug use.…”

“…1,2 Over the past few decades, methods have been developed to monitor the illegal use of these compounds in both humans and animals. [3][4][5][6][7][8][9][10][11][12][13] It is generally accepted that chemical testing of biological fluids is the most objective approach to diagnose drug use. The presence of a drug analyte in a biological specimen can be used to document exposure to that drug.…”