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Title:   Author  item
                                            Hare, Elizabethitem
                                            Norman, Hitem
                                            Wright, Janiceitem
                                            Vanraden, Paul
  Submitted to: Journal of Dairy Science
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 4/7/2004
                                    Publication  Date: 8/1/2004
                                    Citation: Hare, E.M., Norman, H.D., Wright, J.R., Van Raden, P.M. 2004. Duration of herd participation in Dairy Herd Improvement milk recording in the United States. Journal of Dairy Science. 87(8):2743-2747.Interpretive Summary: Patterns of herd participation in Dairy Herd Improvement milk recording were studied to evaluate differences geographically and over time.  The objective was to access the stability of the data collection process used for genetic evaluation.  Herds in the northeastern and mideastern US tended to remain on test longest (7.8 and 8.3 yr, respectively) in recent years.  Shortest time on test (5.1 yr) occurred in the southeastern US.  Duration of participation tended to increase over time from 1960 to 2002.  Many herds entered and exited the testing program multiple times, which caused gaps in testing data that could have resulted in substantial loss in the accuracy of information available for both management and genetic purposes.  Even in the most recent data (2000-2002), 13% of herds initiating testing during that period already had at least one gap of 6 months or more. The results from this study may aid those who provide Dairy Herd Improvement services to dairy producers in focusing on how to keep herds on test which would thereby increase the amount of data available for genetic evaluations.
                                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. To investigate patterns of herd participation in Dairy Herd Improvement testing, periods of continuous testing (interval between milk weights for the herd was '6 mo) were computed based on the year that a herd initiated or terminated testing and by geographical region. Some herds discontinued testing and then re-enrolled. Herds with one period of continuous testing (no testing lapse) accounted for about 65% of the population from 1960 through 2002. Percentage of herds with testing lapses decreased as number of lapses increased and as initial test year became more recent; overall only about 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 continuous testing of '20 yr, which increased to 13% for 2000 through 2002. Herds with more recent termination dates tended to remain on continuous test longer, and one-third of herds that were still on test after June 2002 had been on test for at least 20 yr. Duration of herd participation was longest for the northeastern and mideastern United States and shortest for the southeastern United States. Multiple periods of testing with lapses of >6 mo between test periods represent a loss of data that could enhance study and evaluation of genetic characteristics of US dairy cattle.


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