Trends in U.S. Milk Quality Based on Bulk-Tank Somatic Cell Counts

Abstract Text: The objective of this study was to evaluate changes in bulk-tank somatic cell counts (BTSCC) from 2000 to 2012. BTSCC data from four Federal Milk Marketing Orders (FMOs), representing about half of the milk marketed in the United States, were used to evaluate changes in BTSCCs. The four FMOs were: Mideast, Upper Midwest, Central and Southwest. Data were collected monthly and included herd identification, FMO, pounds of milk shipped, and official BTSCC. These data represent all milk shipped through the four FMOs, and conclusions apply only to this population of shipments. Because this study was a census, no estimates of sampling variability were calculated. A milk-weighted, 3-month geometric mean BTSCC was calculated and summed for all herds in each FMO and for all herds. SAS software was used for all calculations. The Upper Midwest FMO accounted for approximately 45% of milk monitored on an annual basis. In 2012, 43.1 billion kg of milk from 309,343 shipments representing 28,274 producers were monitored. The milk-weighted mean BTSCC decreased from 296,000 cells/mL in 2000 to 194,000 cells/mL in 2012, while the producer-weighted mean BTSCC decreased from 320,000 to 230,000 cells/mL during the same period. The Mideast FMO had the lowest BTSCC for 11 of the 13 years evaluated. Seasonal variations in BTSCC were consistent from 2000 to 2012, with the highest counts occurring in July through September. The U.S. BTSCC limit is 750,000 cells/mL; however, some countries that import dairy products from the U.S. have a limit of 400,000 cells/mL. From 2000 to 2012, the percentage of milk shipped from the four FMOs with BTSCCs of less than 400,000 cells/mL increased from 74.8 to 95.6%, while the percentage of shipments with counts less than 400,000 cells/mL increased from 65.0 to 87.4%. The percentage of producers from which all shipments counts were less than 400,000 cells/mL increased from 42.2 to 64.5%.  BTSCCs in the United States have decreased approximately 35% since 2000. Many factors are likely responsible for these improvements in milk quality, e.g., producer motivation in the form of bonuses for providing quality milk, milk-quality regulations of countries that import U.S. dairy products, and an emphasis on improving milking procedures.

Keywords: BTSCC milk quality