CDCB RESEARCH REPORT K2-13 (2-15)

State and national standardized lactation averages by breed for cows calving in H.D. Norman and L.M. Walton Council on Dairy Cattle Breeding 301-525-2006~ duane.norman@uscdcb.com ~ https://uscdcb.com

Lactation yields are often standardized to provide a reasonably equitable comparison of dairy animals having different lactation characteristics (e.g., calving age, days milked, milking frequency, etc.). This annual report provides averages of standardized yield coming from herds enrolled in Dairy Herd Improvement (DHI). The averages are summarized for cows and heifers that calved during for each state and the nation by breed. It includes a few Mexican herds tested through the U.S. DHI system as well. The test-day data used by the Council on Dairy Cattle Breeding to calculate the standardized yield were provided by the dairy records processing centers (DRPC); reports showing participation in DHI programs on January 1, 2015 and DRPC activity on January 1, 2015 have been summarized also using the same data source. Only data used in calculation of national genetic evaluations (see complete evaluation documentation) are included in the state and national averages. Thus, records beyond fifth lactation were excluded, as were those from cows that lacked a first-lactation record or had missing sire identification.

Breed yields are different between this report and the herd-average report. This report summarizes standardized lactation yield (yield adjusted to 305 days, twice daily milking, for month of calving, and to a mature-age basis). In contrast, the herd-average report is determined from actual herd yields. Herd-averages reported are not restricted to records usable for national genetic evaluations. The herd-averages are impacted by lactation length and dry period. Relative yields among breeds differ between the two reports because of large breed differences in the percentage of usable records and age-parity factors. The herd-average reports is more current than this standardized yield report and provides a more accurate comparrison of actual breed productivity.

Lactation records were first calculated with the best prediction method in 1997 and are standardized for age-parity (lactation number), calving month, previous days open, and times milked per day. Records shorter than 305 days are extended to 305 days as part of the best prediction process. Prior to 1997, lactation records were calculated with the test-interval method. The change in methods was responsible for a part of the yield increases shown between 1995 and 2000 because predicted yield for low-producing cows is higher using best prediction than using the test-interval method. 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, respectively. Component percentages were computed from averages of standardized yields for milk and fat or protein.

Numbers of records and national averages for milk and component yields and component percentages are in Table 8A-F by breed for selected years. Holsteins, Jerseys and Red and Whites had more usable lactations (Table 8A) in 2013 than in 2012. Holstein calvings were up 0.8%; Jersey calvings increased by 10.8%. Compared with 2012, milk yield (Table 8B) increased for 4 of the 7 breeds; Ayrshires by 0.2%, Holsteins by 1.2%, Jerseys by 2.2%, and Red and White by 0.5%. Fat percentage (Table 8C) showed increases from 2012, rising from .02 to .06 in all 7 breeds. Fat yield (Table 8D) in 2013 increased by 4 pounds in Brown Swiss, 5 pounds in Guernsey, 9 pounds in Ayrshires, 11 pounds in Red and Whites, 16 pounds in Holstein, and 25 pounds in Jerseys. Protein percentage (Table 8E) remained the same for Milking Shorthorn and Red and Whites but increased by .01 or .02 percentage units for the remaining 5 breeds. Examining milk components across the last decade clearly reveals success in increasing both fat and protein poercentages. Average protein yield (Table 8F) increased by 1 pound for Ayrshires and Brown Swiss, 5 pounds for Red and Whites, 13 pounds for Holsteins, and 19 pounds for Jersey since 2012.

A number of factors affect production averages including milk, beef, and feed prices, government programs, and characteristics of herds entering and leaving eligible testing programs. These average yields over time also reflect changes in management strategies, and the apparent shift of genetic emphasis toward other health and fitness traits. Still, genetic selection continues to have a positive effect on the milk traits. Interpretation of trends in lactation averages should be made in view of all the factors affecting profitability.

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