Journal of Dairy Science, Vol 77, Issue 5 1466-1476, Copyright
© 1994 by American Dairy Science Association
Records contributing to national genetic evaluations by year, registration
status, herd size, and region
T. R. Meinert and H. D. Norman
Animal
Improvement Programs Laboratory, Agricultural Research Service, Beltsville, MD
20705-2350.
Lactation records from official DHIA were screened for usability in
computing USDA-DHIA genetic evaluations. Counts of usable lactation
records by state, registration status, and year were examined. Number
of cows enrolled in official record-keeping plans of DHIA was the
denominator for calculation of percentage of official DHIA records
usable in genetic evaluations for state-years. Percentage of official
records usable for genetic evaluations had a small increase from 44%
during 1968 to 49% during 1978, had a steep increase through 1988
(65%), and then showed little change during the last 2 yr. Number of
usable records of registered cows for genetic evaluations increased
from 604,570 during 1968 to 864,630 during 1990, which, nevertheless,
represented a decline from 64% of all usable records during 1968 to
only 42% during 1990. Effects of year, DHIA region, average herd
size, and average percentage of registered cows were important for
explaining variation in percentage of records usable for genetic
evaluations for state-years. States with large average herd sizes and
low percentages of dairy cows that were registered had low percentages
of records usable for genetic evaluations. Increased official DHIA
participation and improved sire identification increases the percentage
of records usable for genetic evaluations and helps facilitate
genetic improvement.
