Determination of Bacitracin-MD in Complete Feed by Microbiological Plate Assay: Collaborative Study

Abstract

Eleven laboratories evaluated the double extraction procedure for the determination of bacitracin methylene disalicylate in swine and poultry feeds at 22, 44, and 88 g/2000 lb. Bacitracin activity was determined on each of 2 days using blind duplicates in a random order. All collaborators submitted their data for statistical evaluation. No significant difference was found between the assay results and the label claim at 22,44, and 88 g/2000 lb for swine and poultry feed. For both feed types, reported ranges at 95% confidence limit for 22,44, and 88 g/2000 lb were 17-30 g/2000 lb, 29-61 g/2000 lb, and 64-112 g/2000 lb, respectively. The microbiological plate assay procedure for determination of BMD in complete feed was adopted first action by AOAC INTERNATIONAL.