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A Comparison of the Leucocyte Count, the Brom Thymol Blue Reaction and the Catalase Content of Freshly Drawn Milk

Washington Agricultural Experiment Station, Pullman, Washington

ABSTRACT

A comparative study of the brom thymol blue reaction, the catalase test and the leucocyte content was made of 1019 samples of freshly drawn milk. Milk samples from cows in the advanced stages of lactation or that had just freshened were not included in this study.

Based on the leucocyte content per cc. the samples were grouped as follows: less than 100,000; 100,000–250,000; 250,000–500,00; 500,000–750,000; 750,000–1,000,000; 1,000,000–2,000,000; and over 2,000,000.

In the order of the above increasing leucocyte content, the following percentage of the various groups of samples reacted normally to the brom thymol blue test: 99.0, 94.9, 79.0, 48.4, 43.0, 17.3 and 18.7. In each group a smaller percentage of the samples reacted normally to the catalase test than to the brom thymol blue test. These respective percentages were as follows: 88.5, 66.5, 39.5, 31.0, 8.0, 3.9 and 3.1.

An average leucocyte count of 225,000 was obtained for 870 samples of milk drawn from 31 cows that at all times during the period of observation were free from pronounced positive evidence of mastitis as indicated by the production of stringy or flaky milk. The average cell count of 850 samples reacting negatively to the brom thymol test was 208,000 per cc. as compared to 151,000 for the 654 samples having a catalase index of less than 1.5 cc. The average leucocyte count of 700 samples coming from 103 udder quarters that at all times during the period of observation produced milk giving a normal reaction to the brom thymol blue test was found to be 160,000 per cc. Thirty-nine udder quarters from 19 cows produced milk that at no time showed an excessive catalase content. The average cell count for 247 samples of such milk was found to be 72,000 per cc.

The results of this study indicate that the percentage of animals producing milk, that is normal to both the brom thymol blue and catalase tests, from all quarters and at all times is low.

The average cell count of milk drawn from healthy normal udders is very much less than the average cell count of normal milk as reported by the earlier investigators and by some of the more recent contributors to the subject.