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Journal of Dairy Science Vol. 72 No. 1 194-201
© 1989 by American Dairy Science Association ®
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Genetics of Reproduction in Primiparous Holsteins1

M. A. Faust, B. T. McDaniel and O. W. Robison

Department of Animal Science, North Carolina State University, Raleigh 27695-7621

ABSTRACT

Effects of genetics and relationships between yield and days from parturition to first service, first service conception rate, number of services, and a reproductive performance code based on several reproductive components were investigated in primiparous Holsteins. Recorded breedings and DHI production records were from 3393 daughters of 174 bulls in six experimental herds. Subsets included progeny of 78 sires, with >= 5 daughters calving in April through July (n = 817) and August through March (n = 1162). Daughter-dam regressions (n = 2593 pairs) and paternal half-sibs were used to estimate heritabilities of fertility traits and associations between yield and reproduction. Results showed increased FCM was associated with lowered fertility. For paternal half-sibs, the greatest antagonism was between conception rates and FCM (rG = –.65 ± .10). Daughterdam regressions estimated a favorable genetic correlation of .43 ± .32 between conception rates and yield. Heritabilities were highest for April through July calvings and ranged from .08 ± .10 for first service conception to .24 ± .12 for reproductive code. Correlations between sire least squares constants from warmer and cooler calving seasons were lower than heritabilities of traits would suggest.

FOOTNOTES

1 Paper Number 11,642 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh 27695-7643.






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Copyright © 1989 by the American Dairy Science Association ®.