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Animal Improvement Programs Laboratory, ARS, USDA, Beltsville, MD 20705-2350
Corresponding author: E. Hare; e-mail: lhare@aipl.arsusda.gov.
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 (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 6-mo 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). The percentage of herds with testing lapses
decreased as the number of lapses increased and as the initial test
year became more recent; overall, only 1.5% of herds had more
than 6 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 years 2000 to 2002. Herds with more recent termination dates had
remained 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.
The 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 have enhanced the
study and evaluation of genetic characteristics of US dairy
cattle.
Key Words: Dairy Herd Improvement · milk recording · herd participation
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