Submitted to: AIPL Research Reports
Publication Type: Government Publication
Publication Acceptance Date: May 16, 2000
Publication Date: N/A
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 year 2000 State and national lactation averages were from 1998 calvings sand included the second full year of owner-sampler records. Also, 1998 was the second year that lactation records were computed with the best prediction method. New adjustments for milking frequency are being phased in, and two-thirds of the difference in factors was implemented for 1998 calvings. Component percentages were computed from mean standardized milk and component yields; protein testing is at or near 100% except in California. Only information for a cow's first five lactations was included, but first-lactation data were required for any other information to be included. Numbers and mean standardized yields initiated in 1998 and eligible to contribute to genetic evaluations were documented by State and breed. Numbers of records continued the decline of recent years, but mean yields for milk, fat, and protein were at new highs for most breeds. Component percentages relative to 1990 tended to be similar for protein and lower for fat. Jerseys remained the highest for both component percentages but showed a large decline for fat percentage since 1990. Use of these statistics, which provide an important reference for comparison of State production levels, will aid in maintaining the competitive position of the U.S. dairy cattle population worldwide.