The usefulness of the Wisconsin Mastitis Test in an abnormal milk program is dependent, in large measure, on the degree of its correlation with the direct microscopic leucocyte count. This correlation is dependent to a large degree on the accuracy with which the microscopic count is performed. One of the most likely sources of error in the microscopic count is the criteria for recognizing leucocytes in milk. Wisconsin test results were compared with the microscopic method using counting criteria: whole leucocytes only, whole leucocytes plus damaged cells at least 50% intact, and whole leucocytes and all cell fragments. The results of 117 milk sample comparisons indicated that microscopic Procedures 1, 2, and 3 showed a good correlation with the Wisconsin test (r1 = 0.88, r2 = 0.82, r3 = 0.79), but Procedure 1 was best for predicting Wisconsin test values. © 1968, American Dairy Science Association. All rights reserved.
