Population dynamics of bulk milk somatic cell counts

Area of Science:

• Dairy Science
• Animal Husbandry
• Agricultural Economics

Background:

• Bulk milk somatic cell count (SCC) is a key indicator of udder health and milk quality in dairy herds.
• The European Community introduced a quota system in 1984, impacting dairy farm management practices.
• Previous research indicates seasonal variations and herd-specific factors influence SCC levels.

Purpose of the Study:

• To analyze the population dynamics of bulk milk SCC in Dutch dairy farms over a six-year period.
• To model the impact of regulatory changes, specifically the reduction of the SCC limit, on herd SCC levels.
• To predict farmer responses and potential penalties under new SCC regulations.

Main Methods:

• Analysis of bulk milk SCC data from approximately 27,000 Dutch dairy farms spanning six years.
• Statistical analysis to identify the effects of the quota system introduction and seasonal variations on SCC.
• Development and application of a state transition model to simulate SCC dynamics and farmer reactions to regulatory changes.

Main Results:

• A marked decline in bulk milk SCC was observed coinciding with the 1984/1985 introduction of the European Community quota system.
• Significant seasonal effects on SCC were identified, with peaks in October and troughs in April.
• Simulations indicated that a reduced SCC limit (from 750,000 to 500,000) would decrease mean annual SCC but not significantly increase the number of very low SCC herds (<150,000).

Conclusions:

• The European Community quota system effectively influenced bulk milk SCC reduction in Dutch dairy farms.
• Herds with lower baseline SCC (<450,000) demonstrated greater stability, while higher SCC herds were more variable.
• Simulated stricter SCC regulations are likely to result in increased penalties for a larger number of farmers.