Microbiological assay of avoparcin in animal feeds and pre-mixes

Abstract

A microbiological method for the determination of avoparcin in animal feeds (10–20 mg kg^–1; lowest limit of determination 2 mg kg^–1) and pre-mixes (20 g kg^–1) is described. The method has been submitted to collaborative study by a UK Committee and six other EEC Member States, and gave mean recoveries of 92.8, 104.2 and 101.8% with standard deviations 17.6, 14.0 and 14.6% absolute from chick mash, pig meal and pre-mix, respectively. In the method, the sample is extracted with a mixture of acetone, water and hydrochloric acid, and the antibiotic activity of the clarified extract is determined by measuring the diffusion of avoparcin in an agar medium inoculated with Bacillus subtilis.