Pregnancy rate and first-service conception rate in Angus heifers

J. Minick Bormann, L. R. Totir, S. D. Kachman, R. L. Fernando, D. E. Wilson

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

The objective of this project was to determine the genetic control of conception rate, or pregnancy percentage in Angus beef heifers. Producers from 6 herds in 5 states provided 3,144 heifer records that included breeding dates, breeding contemporary groups, service sires, and pregnancy check information. Two hundred fourteen sires of the heifers were represented; with 104 sires having less than 5 progeny, and 14 sires having greater than 50 progeny. These data were combined with performance and pedigree information, including actual and adjusted birth weights, weaning weights, and yearling weights, from the American Angus Association database. Heifer pregnancy rate varied from 75 to 95% between herds, and from 65 to 100% between sires, with an overall pregnancy rate of 93%, measured as the percentage of heifers pregnant at pregnancy check after the breeding season. Pregnancy was analyzed as a threshold trait with an underlying continuous distribution. A generalized linear animal model, using a relationship matrix, was fitted. This model included the fixed effects of contemporary group, age of dam, and first AI service sire, and the covariates of heifer age at the beginning of breeding, adjusted birth weight, adjusted weaning weight, and adjusted yearling weight. The relationship matrix included 4 generations of pedigree. The heritability of pregnancy and first-service conception rates on the underlying scale was 0.13 ± 0.07 and 0.03 ± 0.03, respectively. Estimated breeding values for pregnancy rate on the observed scale ranged from -0.02 to 0.05 for sires of heifers. Including growth traits with pregnancy rate as 2-trait analyses did not change the heritability of pregnancy rate. As expected for a reproductive trait, the heritability of pregnancy rate was low. Because of its low heritability, genetic improvement in fertility by selection on heifer pregnancy rate would be expected to be slow.

Original languageEnglish (US)
Pages (from-to)2022-2025
Number of pages4
JournalJournal of animal science
Volume84
Issue number8
DOIs
StatePublished - Aug 1 2006

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conception rate
Pregnancy Rate
Angus
pregnancy rate
sires
heifers
Breeding
pregnancy
heritability
Weights and Measures
Pregnancy
weaning weight
yearlings
birth weight
pedigree
Pedigree
Weaning
Birth Weight
breeding season
herds

Keywords

  • Beef cattle
  • Fertility
  • Genetics
  • Pregnancy

ASJC Scopus subject areas

  • Animal Science and Zoology

Cite this

Pregnancy rate and first-service conception rate in Angus heifers. / Bormann, J. Minick; Totir, L. R.; Kachman, S. D.; Fernando, R. L.; Wilson, D. E.

In: Journal of animal science, Vol. 84, No. 8, 01.08.2006, p. 2022-2025.

Research output: Contribution to journalArticle

Bormann, JM, Totir, LR, Kachman, SD, Fernando, RL & Wilson, DE 2006, 'Pregnancy rate and first-service conception rate in Angus heifers', Journal of animal science, vol. 84, no. 8, pp. 2022-2025. https://doi.org/10.2527/jas.2005-615
Bormann, J. Minick ; Totir, L. R. ; Kachman, S. D. ; Fernando, R. L. ; Wilson, D. E. / Pregnancy rate and first-service conception rate in Angus heifers. In: Journal of animal science. 2006 ; Vol. 84, No. 8. pp. 2022-2025.
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