Ontario Bulk Milk Somatic Cell Count Reduction Program. 2. Dynamics of Bulk Milk Somatic Cell Counts

Abstract

The objective of this study was to study the dynamics of bulk milk SCC in order to assist the individual farmer and the dairy industry to lower farm and population SCC. Data on milk quality, milk components, and kilograms of milk produced were collected monthly from January 1985 through September 1991 on approximately 9500 farms in the province of Ontario, Canada. A log-normal distribution was fitted to the SCC data. The log-normal distribution fitted the data reasonably well. This distribution was used to define performance goals for specified regulatory limits. Dynamics of farms were studied using a modified Markov model. Farms with bulk milk SCC from 300 × 103 to 599 × 103 were mostly responsible for a decrease, and farms with bulk milk SCC from 0 to 299 × 103 were mostly responsible for an increase in mean SCC. The SCC contribution, a parameter based on the number of cells that are produced on a farm, was calculated for each farm. Most farms with high SCC did not have high SCC contributions. Farms with high SCC contributions typically had bulk milk SCC from 500 × 103 to 750 × 103. In order to keep population SCC low, an incentive should be offered to farms with low SCC. © 1992, American Dairy Science Association. All rights reserved.