EVALUATION OF 5 SCREENING TESTS USED FOR ESTIMATING LEUCOCYTE COUNTS IN BULK MILK

Five screening tests, Direct Microscopic Leucocyte Count, Wisconsin Mastitis Test, California Mastitis Test, Clemson Catalase Test, Wisconsin Catalase Test, used in estimating leucocyte concentrations were evaluated using 1,308 producer milk samples and 97 tank-delivered samples. These milk samples were representative of the South Carolina milk supply. The Wisconsin test was the most reliable method for estimating leucocytes in milk, using the microscopic count for comparison. This applied to both producer and tank-delivered samples. The Clemson and Wisconsin Catalase tests and the California test were not as reliable predictive tests of leucocyte concentration when compared with microscopic count. The leucocyte data were classified into three groups: less than 500,000, 500,000 to 1,000,000, and more than 1,000,000. The microscopic leucocyte count distributions of producer milk samples were 46.6, 42.4, and 11.0%, respectively, and for tank-delivered samples they were 47.4, 43.3, and 9.3%, respectively. © 1969, American Dairy Science Association. All rights reserved.