Comparison of Results of Mastitis-Screening Tests of Milk from Individual and Pooled Cow Quarters

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Abstract
Results from California Mastitis (CMT), Milk Quality, Modified Catalase, and Modified Whiteside tests were compared with Direct Microscopic Leucocyte Count (DMLC) on 525 aseptically collected milk samples from 21 dairy farms in 3 mid-western states. All samples were tested within 3-5 hr. after collection and retested after 48-hr. refrigeration at 1.7 F. The agreement of the various screening tests with DMLC on 420 quarter samples ranged from 84 to 86%; whereas, on 105 pooled quarter samples, the agreement ranged from 79 to 90%. If screening test results were identified as either negative (negative and trace test scores) or positive (1+, 2+, 3+, or equivalent in ctalase activity or DMLC), test scores of all screening tests were identical on 75 and 68% of the milk samples from individual and pooled quarters, respectively. Significant differences between test scores on milk samples from both individual and pooled quarters before and after storage were found only with the CMT test. Milking practices were compared with screening test results. Failure to sanitize teat cup liners significantly increased levels of leucocytes in milk.