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Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350
Corresponding author: Melvin Kuhn; e-mail: mkuhn@aipl.arsusda.gov.
National genetic evaluations for cow fertility were
introduced by the USDA in February, 2003. These evaluations, reported
as daughter pregnancy rate, are based on days open. One
requirement of the evaluation system is that lactations be at least
250 d in milk (DIM) to be included for analysis. The objective
of this research was to develop a predictor of days open, usable
in genetic evaluation, to allow for earlier predicted transmitting
abilities (PTA), especially for young bulls. The final prediction
equation included an overall intercept, the effects of lactation
and calving ease score, the linear and quadratic effects of age
at calving, and a regression on days open based on last breeding.
Data used for estimation were breeding records from 4 dairy records
processing centers for the years 1995 through 1998. Genetic
correlations were 0.91 by d
130, and phenotypic means of predicted days open were in agreement
with means for final days open, indicating that the predictions were
phenotypically unbiased. Comparison of mean PTA based on actual and
predicted days open indicated no bias in PTA, and correlations
between PTA were
0.92 by d 130. The earlier use of data increased reliability
by about 5% for sires between the ages of 4 and 5 yr. The USDA
began using predicted days open for records that are at least
130 DIM in national evaluations starting November, 2003.
Key Words: fertility · genetic evaluation · prediction
Abbreviations: DO = days open · DPR = daughter pregnancy rate · DO_LB = days open based on last breeding
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![]() P. M. VanRaden, A. H. Sanders, M. E. Tooker, R. H. Miller, H. D. Norman, M. T. Kuhn, and G. R. Wiggans Development of a National Genetic Evaluation for Cow Fertility J Dairy Sci, July 1, 2004; 87(7): 2285 - 2292. [Abstract] [Full Text] [PDF] ![]() |
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