ARS | Publication request: SOMATIC CELL COUNTS OF MILK FROM DAIRY HERD IMPROVEMENT HERDS DURING 2003

Submitted to: AIPL Research Reports
Publication Type: Government Publication
Publication Acceptance Date: February 27, 2004
Publication Date: February 2, 2004
Citation: Miller, R.H., Norman, H.D., Sanders, A.H. 2004. Somatic cell counts of milk from Dairy Herd Improvement herds during 2003. Animal Improvement Programs Laboratory Research Report SCC5(2-04). Available: http://aipl.arsusda.gov/publish/dhi/current/sccrpt.htm

Technical Abstract: Test-day data from all herds enrolled in Dairy Herd Improvement (DHI) somatic cell testing during 2003 was examined to assess the status of national milk quality. Cows with records failing AIPL editing procedures were excluded. Somatic cell score (SCS) is reported to AIPL and was converted to somatic cell count (SCC) for calculating herd and State averages. The current legal limit for bulk tank SCC is 750,000 cells/ml for Grade A producers. Nationally, average SCC during 2003 was 317,000 cells/ml Corresponding averages for 1995 through 2002 ranged from 304,000 to 322,000, and the overall trend has been for an increase in SCC of 1700, annually. The percentages of herd test days that exceeded 750,000, 600,000, 500,000, and 400,000 cells/ml during year 2003 were 5.6, 11.0, 18.2, and 30.2, respectively. Thus, 5.6% of test-days from DHI herds were higher than the present legal limit for SCC of bulk tank milk. This may overestimate the percentage of herds that would have exceeded the legal limit for bulk tank SCC on test day because the milk of cows treated for mastitis is excluded from the bulk tank but not excluded from the DHI test. Also, the percentage of herd test days exceeding the legal limit would have been higher than the percentage of herds that were rejected from the market because market exclusion only occurs after repeat violations. Variation among States was large. Average SCC's were lower in the far West and higher in the Southeast, a finding consistent with previous reports. SCC differences between geographically adjacent states were substantial, which suggests that mastitis-control regimens have an impact under similar climatic conditions. Fewer states had greater than 5% of herd test days exceeding 750,000 cells/ml, showing that progress has been made in some areas. Overall, the results for SCC raise concern that the quality of U.S. milk is not improving. Although changes from 2002 to 2003 were small, the trends for increasing percentage of herd testdays above all four thresholds (750,000, 600,000, 500,000 and 400,000 cells/ml) were significant (P <= 01). Greater efforts to improve milk quality are needed.