Somatic cell count (SCC) in Dairy Herd Improvement (DHI) herds enrolled in SCC testing in the US averaged 228,000 in 2010, which was less than the 2009 average of 233,000. This compares to 262,000 in 2008; 276,000 in 2007; 288,000 in 2006; and 296,000 in 2005.
Variation among states remains large, ranging from less than 200,000 to more than 400,000. State average SCC was lower than the national average for mountain and western states, and often higher for southeastern states.
The current federal SCC regulatory limit in the U.S. is 750,000, except in California where it is 600,000. 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 2010 were 18.0%, 10.0%, 5.7% and 2.7%, respectively. The 2.7% of 2010 DHI herd test days that were higher than the current federal 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.