Modification of Interpretation of Microscopic Cell Counts for Application to Screening of Bulk Tank Milk Samples

Abstract

High and low limits were developed from best-fit formulas for WF's of 20,000 and 10,000, assuming critical cut-off levels of 500,000, 1,000,000, and 1,500,000 cells per milliliter. These were tested, using 92 bulk tank samples, for a total of 276 applications. Samples were classified as above, below, or questionable in relation to the selected critical cell count. On approximately 75% of the 276 applications a WF of 20,000 gave a precision for screening purposes at least equivalent to counts made with WF's in the range of 2,500 to 5,000. Of the remaining samples, two out of five were classified above or below on a second count (WF 10,000). The remaining 15% of the applications were very close to the critical levels (2/3 within 10%) and were considered as unclassifiable. Total errors were 1.8%.