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

An instrument for assessing milking management practices was used to i dentify 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 Im provement Association (DHIA) dairies, and the dairy's management pract ices were evaluated on four occasions during November 1988 to July 198 9. The log-transformed BTSCC, question score 5 and category scores wer e subjected to a series of analyses, including principal-component ana lysis, correlation analysis, multivariate analysis of variance (MANOVA ) and stepwise, all-possible-subsets multiple regression. Principal-co mponent analysis was applied to the time-period-specific category scor es and major data reduction was not seen for any time period. The corr elation analyses between category scores revealed 26 pairs with highly significant correlations. These results indicate that although the ca tegories 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 togethe r in a relatively small number of independent components. The MANOVA r esults indicated that there was a significant time-period effect. The regression analysis identified sanitation, milking equipment, cow cond ition, pre-milking procedures and the mastitis control categories as s ignificantly reducing BTSCC.