Jim Dickrell is the editor of Dairy Herd Management and is based in Monticello, Minn.
Proposals for 400,000 SCC Standard Wildly Different
Mar 14, 2011
Politics are likely to come into play when the National Conference on Interstate Milk Shipments meets next month to discuss proposals from National Milk and NMC.
There are currently two proposals—one by the National Milk Producers Federation (NPMF) and the other by NMC, formerly known as the National Mastitis Council. Both get to the same level of 400,000 by Jan. 1, 2014. But the path to that end point is slightly different—and how quickly violation levels are triggered also differs.
The NMPF proposal is far more restrictive and conservative, and triggers more violations much more quickly. The irony in all this lies in the fact that NMPF has dragged its feet in bringing U.S. standards up to par with the rest of the world for more than a decade. It has only been since the European Union (EU) has threatened to cut off U.S. exports that NMPF stepped up to plate.
To its unbeknownst credit, NMPF’s proposal will propel U.S. milk standards to becoming a global leader. And that’s a good thing—for cows, dairy producers and consumers, both domestic and foreign.
USDA’s Animal Improvement Programs Laboratory (AILP) recently analyzed SCC test day records from nearly 15,000 DHI herds with roughly 4 million cows.
This huge DHI data set allows USDA researchers to calculate more closely how many herds and how much milk would exceed federal standards as SCC levels are reduced.
The USDA analysis shows 14.1% of DHI herds (and 5.8% of milk) would not be in compliance if the SCC limit is reduced to 400,000 cells/ml under the NMPF proposal. Under the NMC proposal, which mirrors the EU methodology, 7.8% of herds (and 3.1% of milk) would not be in compliance.
The reasons for these huge differences are twofold:
• First, the EU requires calculating averages geometrically, not arithmetically. The rolling geometric mean would be calculated based on the SCC values from the three most recent months. For the math-impaired, we all learned how to do these calculations in middle school, and then promptly forgot how to do them in high school.
(A refresher: The geometric mean is calculated by converting the SCC values to Log base 10 (Log10), summing the 3 Log10 values, dividing the sum by 3 and converting the value to the arithmetic number by finding the antilog. It sounds complicated, but thankfully, all calculations are easily done on hand-held calculators or desk top computers.)
Mastitis researchers say using the geometric mean is both biologically and statistically the correct method for calculating cell count averages.
It has the added benefit of actually producing a lower average than arithmetic averages. “The use of the rolling geometric mean really helps decrease the number of non-compliance herds,” says Duane Norman, the AIPL supervisory research geneticist who conducted the analysis.
• Second, the EU does not suspend producers until their rolling three-month geometric mean exceeds 400,000 cells/ml. USDA’s Norman interpreted this to mean once the three-month geometric mean reaches 400,000, the producer is then warned and has another three months in which to bring the cell count below 400,000. This is the practice in Germany (though the EU directive 94/46/EEC is actually based on three tests).
NMPF, on the other hand, proposes maintaining the current system to suspend a license if a producer exceeds the standard three out of the most current five months. “Using three of five tests is tougher on producers, no question,” says Norman.
Who is most at risk? It’s long been known that smaller herds and herds in the South struggle to meet the 400,000 SCC level. “The Southeast is definitely running high, and some of the mid-plains states—Arkansas, Kansas, Missouri, Nebraska, Oklahoma—are marginal as well,” says Norman. Click here to see Norman’s analysis; click to Slide 13 for regional comparisons.
How all this sorts out at NCIMS remains to be seen. Despite the claim that NCIMS is a milk safety organization, politics will inevitably come into play. It always does. Stay tuned.