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Abstract
Michigan and Northeast dairy herds that produced young bulls for AI sampling from 1974 to 1981 and 1978 to 1981, respectively, and those involved in progeny testing were compared with their contemporary DHI herds. The 1985 lactation records of Michigan herds and 1980 to 1987 data of Northeast herds were acquired from respective DHIA data processing centers, and genetic evaluation results of sires and cows in those herds were obtained from USDA. Herd average milk production, intraherd SD for milk production, average sire PD of cows and average cow index in the herd, and intraherd SD of sire PD and of cow indexes were computed for each herd-year. These characteristics were used to compare the herd groups. Herds in which young bulls were sampled had greater average milk production, greater variance for milk production, and greater genetic variance than other herd groups. However, these herds were not genetically superior to other herd groups, except that the bull-dam herds in the Northeast have become a superior group since 1985, and the margin of superiority has increased over time. Herds participating in progeny testing of young bulls were by far the most superior group genetically in Michigan, especially those participating in the testing program for more than 10 yr. However, progeny testing herds in the Northeast were similar to herds not involved in sire sampling or testing programs in their average genetic merit.
Key words
Abbreviation key:
BDH (bull-dam herds), CI (cow index), MCC (Modified Contemporary Comparison), OH (other herds), PTH (progeny testing herds for > 10 yr (+) or < 10 yr (−)), 305-ME (305-d mature equivalent milk yield)References
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Article info
Publication history
Accepted:
November 5,
1990
Received:
April 16,
1990
Identification
Copyright
© 1991 American Dairy Science Association. Published by Elsevier Inc.
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