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Title: Consequence of changing standards for somatic cell count on US Dairy Herd Improvement herds

Author
item Norman, H
item Wright, Janice
item MILLER, R - Retired ARS Employee

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/24/2011
Publication Date: 6/30/2011
Citation: Norman, H.D., Wright, J.R., Miller, R.H. 2011. Consequence of changing standards for somatic cell count on US Dairy Herd Improvement herds. Journal of Animal Science 89(E-Suppl. 1)/Journal of Dairy Science 94(E-Suppl. 1):428(abstr. 352).

Interpretive Summary:

Technical Abstract: Consequence of noncompliance with European Union (EU) and current US standards for somatic cell count (SCC) as well as SCC standards proposed by the National Milk Producers Federation was examined for US herds. Somatic cell scores (SCS) from 14,854 Dairy Herd Improvement (DHI) herds were analyzed. Herds had between 15 and 26 DHI tests from Jan. 2009 to Oct. 2010 and >=10 cows. The SCC for individual cows came from their SCS by SCC = 2 **(SCS - 3) x (100,000). As a proxy for bulk tank SCC, herd test-day SCC were derived by weighting each cow's SCC by her test-day milk yield and were the basis for determining herds and milk that were SCC noncompliant. A herd was noncompliant for the EU SCC standard after 4 consecutive rolling 3-test geometric means were >400,000 cells/mL. A herd was noncompliant for US SCC standards after 3 of 5 consecutive SCC tests were >750,000 (current), >600,000 (proposed), >500,000 (proposed), or >400,000 (proposed) cells/mL. Results were examined by month, herd size, and state. For current SCC standards, weighted means for US herd noncompliance from Nov. 2009 through Oct. 2010 was 0.9% for US and 7.8% for EU standards; noncompliance for proposed US SCC standards of 600,000, 500,000, and 400,000 cells/mL were 2.7, 6.2, and 14.1%, respectively. Only a US standard of 400,000 cells/mL was more restrictive than the EU standard. Only 0.2% and 3.1% of US milk failed current US and EU SCC standards, respectively. Compliance for US herds generally increased with herd size. For the current US SCC standard, 1.7% of herds were noncompliant when herd size was <50 cows, but <=0.1% of each of 4 herd groups with >=200 cows were noncompliant. For the EU standard, noncompliance declined from 10.6% for herds with <50 cows to 0.5% for herds with >=1,000 cows. Herd noncompliance ranged from 2 to 15% for 6 states and Puerto Rico for the current US standard and from 20 to 35% for 9 states for the EU standard. If US producers must meet more stringent EU or proposed US standards for SCC, they will need to place more emphasis on sound milking management practices and do more culling to improve milk quality.