Microbiological Assay of Oleandomycin in Feed: Collaborative Study

Abstract

Abstract The present official final action AOAC method of analysis for oleandomycin in feeds, 38.204–38.207, was modified and collaboratively studied. The modifications consist of elimination of the compensating standard curve, changes in the curve point concentrations, and a change in the plating medium. Ten collaborators assayed 4 feed types each at 3 levels of fortification ranging from 1.8 to 18.2 g/ton. All feeds were tested for 2 days, 2 weights per day. The average mean recovery for all feeds at all levels was 92.3% (ranging from 90.11% at the 1.82 g/ton level to 93.51% for the 18.17 g/ton level). The coefficients of variation ranged from 18.2 at the 1.82 g/ton level to 9.3 at the 18.2 g/ton level. The assay variation for all collaborators was 12.5%. No statistically significant differences were found between feed types, levels, and collaborators at the 95% confidence level. This method has been adopted as official first action for the assay of oleandomycin at levels ≤2 g/ton.