Variation in Cell Content of Milk Associated with Time of Sample Collection. I. Diurnal Variation

Data were analyzed to delineate the diurnal variation in body cell content of quarter-milk samples. Frequent foremilk samplings indicate that cell counts arc lowest just prior to milking, rise sharply in the strippings, remain hioh during the next 4 hr, then decrease progressively to a minimum value near the end of the intermilking period. The body cell level and the magnitude of cyclic change varied widely between groups of cows, cows within group, and to a lesser degree between quarters of a cow. These results emphasize the necessity for care in selecting the optimum time of sampling according to the type of hlformation desired in research or routine health sm-veys. Variation in time of sampling can introduce real uncertainty m the interpretation of cell count data.