Submitted to: AIPL Research Reports
Publication Type: Government Publication
Publication Acceptance Date: 3/20/2008
Publication Date: 3/20/2008
Citation: Norman, H.D., Thornton, L.L., Wiggans, G.R. 2008. State and National Standardized Lactation Averages by Breed for Cows Calving in 2006. AIPL Research Reports. K2-06(3-08). Interpretive Summary:
Technical Abstract: Means for dairy cow lactation data used in national genetic evaluations and other USDA research are useful for indicating trends and describing cow populations. Breed lactation means are on a 305-day, twice daily milking, mature-equivalent basis from cows contributing to genetic evaluations. Data for State and national lactation averages were from year 2006 calvings. National averages for prior years have been computed to reflect the change from reporting of crude protein to true protein. Component percentages were computed from mean standardized milk and component yields; protein testing is at or near 100% except in California and Nevada. Numbers of lactations initiated in 2006 and eligible to contribute to genetic evaluations, and mean standardized yields were documented by State and breed. Number of calvings for 2006 increased by 1.1 to 13.6% for all breeds except Guernsey which declined by 5.8%. Holsteins and Jerseys increased by 4.3 and 7.3%. Milk yield was virtually unchanged (-0.4 to +0.4%) for all breeds but Guernseys which increased by 1.4%. A failure for milk yield to increase is unusual, but might have been expected with the large increase in cow numbers, reflecting less culling.