Somatic cell count (SCC) in Dairy Herd Improvement (DHI) herds enrolled in SCC testing in the United States averaged 200,000 cells/ml in 2012, which was less than the 217,000 average during 2011. This compares to 228,000 in 2010 and 233,000 in 2009. National average test-day herd SCC has declined every year since 2005, and every year except one since 2001.
The current federal SCC regulatory limit in the US is 750,000. In many other major dairy countries, the SCC limit is 400,000.
The overall percentage of herd test days that exceeded 400,000, 500,000, 600,000, and 750,000 during 2012 were 12.0%, 6.1%, 3.3% and 1.5%, respectively, which was lower for all levels than during 2011. The 1.5% of 2012 DHI herd test days that were higher than the present legal limit for bulk tank SCC in the US may overestimate the percentage of herds that shipped milk exceeding the legal limit because milk of cows treated for mastitis is excluded from the bulk tank even though included in DHI test data. The percentage of herd test-days that exceeded the legal limit also would have been higher than the percentage of herds that were rejected from the market because market exclusion only occurs after repeated violations.