Collaborative study of a microbiological assay for lasalocid sodium in feeds

The microbiological cylinder plate assay method for lasalocid sodium reported earlier was studied in a slightly modified form by 7 laboratories. Assay values paralleled recovery values and all data were corrected by the corresponding daily recovery factor for the feed type. Agreement between laboratories for mashes and pellets containing 0.0064, 0.0080, and 0.0096% lasalocid sodium was satisfactory. Coefficients of variation for mashes were 14.6, 9.8, and 10.7% and for pellets, 15,2, 10.9, and 15.6%. The average of the values found for the 3 mashes was 99.4% of the calculated value and for the 3 pellets, 86.5%. The method has been adopted as official first action.