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item NORMAN, H

Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: 4/29/2004
Publication Date: 4/29/2004
Citation: Hare, E.M., Norman, H.D., and Wright, J.R. In: Duration of herd participation in Dairy Herd Improvement milk recording in the United States [abstract]. Proceedings of Beltsville Agricultural Research Center Poster Day 2004, April 29, 2004, Beltsville, MD. Abstract 39.

Interpretive Summary:

Technical Abstract: Participation in milk-recording programs that provide data for national genetic evaluations of dairy cattle in the United States is voluntary, but the effectiveness of the evaluation system increases with the number of herds that contribute data. Genetic evaluations are used by breeders as a quantitative measure of an individual's merit for the purpose of selecting breeding stock for future generations. To investigate patterns of herd participation in Dairy Herd Improvement (DHI) testing, periods of continuous testing were computed based on the year that a herd initiated or terminated testing and by geographical region. Continuous testing was defined as at least one test per six-month period. Some herds discontinued testing and then re-enrolled. Across all years (1960 through 2002), 65% of herds had one period of continuous testing (no testing lapse). Percentage of herds with testing lapses decreased as number of lapses increased and as initial test year became more recent; overall only 1.5% of herds had more than six continuous testing periods. For herds that terminated DHI testing from 1960 through 2002, 64% were on continuous test for <3 yr. In general, herd frequencies decreased as continuous test period increased except for those herds testing >20 yr, which increased to 13% for the 2000-2002 period. Herds with more recent termination dates had remained on continuous test longer, and one-third of herds that were still on test after June2002 had been on test for at least 20 yr. Duration of herd participation in DHI testing varies considerably by region. Since 1980, participation was shorter than the US mean for herds in the Southeast, Midwest, and Southwest. Herds in the northeast had the longest time on test before 1990, but they have since fallen behind the Mideast. From 1995 through 2002, herds in the Northeast and Mideast remained on test longest (7.8 and 8.3 yr, respectively); the shortest time on test (5.1 yr) occurred in the Southeast. Herds that have multiple periods of testing with lapses of >6 mo between test periods represent a loss of data that has a negative impact on research and genetic improvement. Determining the reason for these lapses and trying to eliminate them could benefit the dairy industry considerably.