Development of an immunochromatographic assay for the β-adrenergic agonist feed additive zilpaterol

ABSTRACT

Zilpaterol is a β-adrenergic agonist feed additive approved in the United States to increase weight gain and improve feed efficiency of cattle. A zilpaterol immunochromatographic assay was developed as an economical and user-friendly rapid detection method for zilpaterol and validated using urine and tissue samples derived from animal studies. The assay sensitivity was 1.7–23.2 ng g⁻¹ or mL⁻¹ across a variety of feed and animal matrices and did not cross-react with clenbuterol or ractopamine. No sample pre-treatment of cattle and sheep urine was needed, but horse urine and feed required dilution; skeletal muscle required solvent extraction prior to testing. Of 32 incurred sheep urine samples tested, zilpaterol content was correctly identified in all but 2 samples. Horse urine containing >10 ng mL⁻¹ of incurred zilpaterol residue (n = 48) was correctly identified as zilpaterol positive. The assay correctly identified 0-day withdrawal sheep muscle samples as zilpaterol positive and the control and longer withdrawal day sheep muscle samples as negative. Zilpaterol was demonstrated to be stable in horse urine when stored at −20°C for 7 years.

KEYWORDS:

• Zilpaterol
• immunoassay
• residues
• on-site test
• screening
• stability

Acknowledgements

The authors wish to thank Jasmine Hanson, Amy McGarvey, Jason Holthusen and Kira Rahn for skilful technical support. Control horse urine was provided by Dr Carolyn Hammer at North Dakota State University and is greatly appreciated. Our gratitude is extended to Dr Mark West for consultation on statistical analyses.

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Disclosure statement

No potential conflict of interest was reported by the authors.