Relationship between California Mastitis Test Reaction and Production and Composition of Milk from Opposite Quarters

Abstract

The relationship between the California Mastitis Test (CMT) reaction of milk from individual quarters and production was determined by comparing the production at a single milking, of opposite quarters of the same udder which differed in CMT reaction. Comparisons were obtained for 1,258 opposite-quarter milkings from 763 cows in 30 dairy herds. These opposite-quarter comparisons were well distributed over the lactation period, season of year, and between front and rear halves of the udder. Test reactions (on total quarter milk) of trace, 1, 2, and 3 were associated with average decreases in milk production of 0.42 (9.0%), 0.95 (19.5%), 1.72 (31.8%), and 2.33 (43.4%) kg per quarter per day, respectively.Test reactions of foremilk from 6,600 quarters were distributed as follows: Negative, 36.7%; trace, 14.4%; 1, 27.8%; 2, 10.9%; and 3, 9.6%. Only 0.6% of the quarters were blind or dry at the time of examination.A comparison of the CMT reaction of foremilk and total quarter milk from 3,047 quarters revealed that the two CMT readings were in agreement for 82.5% of the comparisons.