AIPL RESEARCH REPORT K2-99 (3-01)

State and National Standardized Lactation Averages by Breed for Cows Calving in 1999 R.L. Powell and A.H. Sanders Animal Improvement Programs Laboratory, ARS-USDA, Beltsville, MD 20705-2350 301-504-8334 (voice) ~ 301-504-8092 (fax) ~ rlaipl@aipl.arsusda.gov ~ http://aipl.arsusda.gov

Data for year 2001 State and national lactation averages were from calvings in 1999. National averages for some prior years were computed to reflect the change from reporting of crude protein to true protein and are also presented.

Yield data that are used in national genetic evaluations of dairy cattle and in other U.S. Department of Agriculture research originate from herds that are enrolled in the Dairy Herd Improvement program. The test-day data, used by the Animal Improvement Programs Laboratory to determine lactation records, are provided through dairy records processing centers.

Lactation records were calculated using the best prediction method and were standardized for age-parity, calving month, previous days open, and times milked per day. Records in progress and other records that were shorter than 305 days were extended to 305 days as part of the best prediction process. Component percentages were computed from average standardized yields for milk and components. Protein testing is at or near 100% except in California (85% for Holsteins).

Only data used in the calculation of national genetic evaluations are included in the State and national averages. Thus, records beyond fifth lactation or by cows that lacked a first lactation record were excluded.

The numbers of records and averages for yields and component percentages are in Tables 1 through 7 by State for Ayrshires, Brown Swiss, Guernseys, Holsteins, Jerseys, Milking Shorthorns, and Red and Whites. The numbers of records and national averages are in Table 8 by breed for selected years.

Breed yields are different between this report and the herd-average report because this report uses standardized data, whereas herd averages are based on rolling actual data. Also, data for cows that calve in 1999 contribute to herd averages for 1999 and 2000. Finally, herd-average data do not have a restriction that they must be usable for national genetic evaluations. Relative yields among breeds will differ between the two reports because of breed differences in percentage of usable records and differences in age-parity factors.

The trend of recent years for a decrease in numbers of records was reversed in four breeds, but a meaningful increase occurred only for Jerseys (4.6%) and Holsteins (1.6%). Average yields were at new highs for all breeds and traits. The change from crude to true protein lowered the reported values for protein percentage by 0.19. Component percentages relative to 1995 tended to be similar for most breeds but fat percentage decreased for Jerseys and Red and Whites, and protein percentage increased for Guernseys, Holsteins, and Red and Whites. On average across breeds, protein percent increased by 0.02 and fat percent decreased by 0.01.

Changes in the numbers of records and average yields result from many factors. Genetic change is expected to have a positive effect on yield, whereas feed availability and other operating costs, milk and beef prices, Government programs, and characteristics of herds entering and leaving eligible testing programs can affect production averages in either direction.