Validation methods for the determination of β agonists residues in feed

Veterinary drugs are widely used in modern animal husbandry. Their usage is not only for therapeutic and prophylactic purposes but also for better breeding efficiency. A part of veterinary drugs are used as growth promoters in form of specified compounds or mixtures of compounds. Therefore, among other compounds, steroids and other substances that have similar pharmacological activity are used to improve efficiency of protein conversion. As a result of enhanced protein conversion the growth of animals is faster which lead to earlier slaughter. The aim of this study was to detect levels of β – agonist residues since they are used as additives in the feed. By using ELISA method level of β – agonist was determinate. Total of 49 feed samples were screened for the presence of β–agonist as a part of national monitoring residue plan. The feed samples were collected and delivered by the authorised veterinary inspectors within period of 1 year. The validation process was carried out according to Commission Decision 2002/657/EC criteria. Limit of detection (LOD) for β–agonist in feed was determined to be 0.63 ng/ml. The recovery was between 71.8% and 77.2%, a working range between 0.3 to 25.0 ng/ml. The regression equation of the final inhibition curve was: y=- 0.1143∙Ln(x)+0.5906, R2=0.9904. Additionally detection capability ( CCβ) was 5.46 ng/ml. The levels of β – agonist residues were below the international allowable levels set by the Macedonian Residue Control Plan and the European Union. According to this study for β – agonist, feed in Republic of Macedonia is free and safe for animal consumption. However, it is necessary further monitoring of these chemicals as a food quality control measure. Shown data in this study will be helpful for screening of β – agonist residues and regulations on its illegal use in feed.