THE ASSOCIATION OF MILKING MANAGEMENT-PRACTICES WITH BULK TANK SOMATIC-CELL COUNTS

An instrument for assessing milking management practices was used to identify factors associated with udder health. The instrument included 48 individual management variables in 12 categories. Bulk tank somatic cell count (BTSCC) was recorded on 56 randomly selected Dairy Herd Improvement Association (DHIA) dairies, and the dairy's management practices were evaluated on four occasions during November 1988 to July 1989. The log-transformed BTSCC, question score 5 and category scores were subjected to a series of analyses, including principal-component analysis, correlation analysis, multivariate analysis of variance (MANOVA) and stepwise, all-possible-subsets multiple regression. Principal-component analysis was applied to the time-period-specific category scores and major data reduction was not seen for any time period. The correlation analyses between category scores revealed 26 pairs with highly significant correlations. These results indicate that although the categories in the instrument were correlated to the degree that some of the correlations were statistically significant, the strengths of the correlations were not sufficient for the categories to cluster together in a relatively small number of independent components. The MANOVA results indicated that there was a significant time-period effect. The regression analysis identified sanitation, milking equipment, cow condition, pre-milking procedures and the mastitis control categories as significantly reducing BTSCC.