400,000 Cells, But Who’s Counting?

Published on: 11:03AM Apr 25, 2011

The new regulation for milk quality standards will have a profound effect on U.S. dairies. It’s the first step on the path to ensuring high quality milk is entering the food supply.

Delegates to the National Conference of Interstate Milk Shipments meet this week in Baltimore. In all likelihood, they will improve U.S. milk standards by lowering the allowable somatic cell limit to 400,000 cells/ml.
This is more than a decade in coming. Even then, exactly what is passed will have a profound effect on how the new regulation impacts U.S. dairy farms.
The National Milk Producer Federation (NMPF) proposal says a farm would be out of compliance (and unable to ship milk) if three of five consecutive somatic cell count (SCC) tests exceed 400,000 cells/ml. The National Mastitis Council (NMC) proposal says a farm will be out of compliance if the three-month geometric mean SCC plus the next SCC test exceeds 400,000.
NMPF’s three-of-five month procedure is currently what exists in the Pasteurized Milk Ordinance and is simple to administer. The NMC procedure is more complicated because the geometric mean must continually be calculated each month, but it is both biologically and mathematically the correct way to evaluate the subclinical mastitis levels in a herd. It also results in lower SCC averages and in fewer herds out of compliance.
USDA’s Animal Improvement Programs Laboratory recently used DHIA herd tests to calculate the number of non-compliant herds under the NMPF and NMC proposals. The months evaluated were November 2009 through October 2010.
Under the NMPF plan, the number of non-compliant herds ranged from a low of 12.9% in March 2010 to a high of 16.4% in September 2010. The weighted average was 14.1%.
Under the NMC plan, the number of non-compliant herds ranged from a low of 7.5% in January 2010 to a high of 11.5% in September 2010. The weighted average was 9%.
Granted, these numbers are generated using historical data. Under both the NMPF and NMC proposals, there will be a phase-in period with the 400,000 SCC standard taking hold Jan. 1, 2014. So, dairy producers will have about two and a half years to prepare.
Getting below 400,000 won’t be good enough, however. If bulk-tank cell counts drop to between 350,000 to 400,000, there’s an 80% to 90% probability cell counts will exceed 400,000 at least once during the next 30 days if cell count variation between milk pick-ups exceeds about 25,000. That’s according to an analysis of two years of 1,500 Upper Midwest bulk- tank SCC records done by veterinarian and milk quality specialist Jeff Reneau and his grad students at the University of Minnesota.
In order to lower the probability of exceeding 400,000 to below 25%, bulk-tank SCCs should be below 200,000, and variation between pick-ups can be no more than 75,000.
Yes, both the NMPF and NMC proposals require multiple months above 400,000 to trigger non-compliance. But herds that consistently exceed 300,000 will have a 50% or higher probability of exceeding 400,000 at least once each month.
Setting the 400,000 SCC standard is the first step on the path to ensuring high quality milk is entering the food supply. The next step will be education and implementation of existing milk quality knowledge.
“We have enough information to get all of our herds under 200,000 cells,” says Reneau. “The problem is we’re not getting compliance or implementation of recommendations. This is not rocket science; we can get it done.”
The good news is that as milk quality improves, milk production jumps significantly. Minnesota DHI records shows that with each one reduction of linear somatic cell score (LnSCS), rolling herd average increases 2,052 lb. Going from LnSCS 5 (400,000 cells/ml) to LnSCS 4 (200,000 cells/ml) means a ton more milk per cow.
So, the time to start improving milk quality and procedure compliance is now. Why wait until Jan. 1, 2014?