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Physiological and Environmental Factors Affecting the California Mastitis Test under Field Conditions^{1, 2, 3,}

Department of Dairy Science, University of Wisconsin, Madison

ABSTRACT

The California Mastitis Test (CMT) was used on quarter samples under field conditions to determine the extent of positive reactions and to identify the physiological and management factors most closely correlated with a high proportion of positive reactions. In Experiment I, 1,417 cows in 45 dairy herds were tested once. CMT and catalase tests were run on the bulk milk. In Experiment II, four herds were tested monthly for ten consecutive months, with 339 cows and 8,653 quarter samples involved. There were 30.6% positive, quarters in Experiment I and 18.0% in Experiment II.

Physiological factors having the greatest effect on the CMT were parity, stage of lactation, and the dry period. First-lactation animals had a markedly lower number of positive quarters than older cows. Positive reactions increased as cows passed mid-lactation. Seventy per cent of quarters positive at the end of a lactation returned to negative following a dry period.

Significant correlations between certain environmental factors and positive reactions on one or more of the screening tests indicated that the following factors were most closely related to a low incidence of positive reactions: small herd size, high yearly production per cow, adequate preparation for milking, maximum sanitation, and minimum vacuum fluctuation during milking.

¹ Published with the approval of the Director of the Agricultural Experiment Station.

² These data are part of a thesis presented by the senior author to the University of Wisconsin in partial fulfillment of the requirements of the degree of Master of Science.

³ Contributions from the Dairy Cattle Research Branch, USDA, Beltsville, Maryland.

⁴ Present address: Dairy and Livestock Research Department, Beacon Feeds, Beacon Division of Textron Inc., Cayuga, New York.