Cell counts and composition of bovine milk

Observations were made on 249 first or second calf heifers in which mastitis had been diagnosed in a mammary quarter which was opposite a normal quarter. Cell counts were made on the milk from each quarter and the cows were divided into three groups with the infected quarters classed according to the cell count. The infected quarters gave lower yields of milk with lower fat, solids-not-fat (SNF) and protein percentages than the opposite normal quarters in all three groups, but the differences between the means were only significant in yield and fat and SNF contents in the two groups with cell counts of over 500,000 per ml. In 175 animals the numbers and diameters of the fat globules were measured. The only significant reduction was in the globule numbers in the cows with from 1 to 2 million globules per ml of milk.