Submitted to: AIPL Research Reports
Publication Type: Government Publication
Publication Acceptance Date: February 12, 2009
Publication Date: February 18, 2009
Citation: Norman, H.D., Ross Jr, F.A. 2009. State and National Standardized Lactation Averages by Breed for Cows Calving in 2007. AIPL Research Reports. K2-07 (2-09).
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 2007 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 100%. Numbers of lactations initiated in 2007 and eligible to contribute to genetic evaluations, and mean standardized yields were documented by State and breed. Number of calvings for 2007 increased by 4.2 and 4.4% for Holsteins and Jerseys; the other breeds showed a small decline. Milk yield was down slightly (-0.1 to -0.9%) for all breeds but Brown Swiss and Jerseys which increased by 0.6%. A failure for milk yield to increase is unusual but most likely reflect changes in management strategies considering milk and feed prices and more emphasis on other traits such as health and longevity.