| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
,3
* Department of Animal Science, University of Nebraska, Lincoln 68583-0908 USDA, ARS, Roman L. Hruska U.S. Meat Animal Research Center,
and
Clay Center, NE 68933 and
and
Lincoln, NE 68583-0908
3 Correspondence:
A218 Animal Sciences, University of Nebraska (phone: 402-472-6010; fax: 402-472-6362; E-mail:
lvanvleck{at}unlnotes.unl.edu).
Records for yearling scrotal circumference (SC; n = 7,580), age at puberty in heifers (AP; n = 5,292), age at first calving (AFC; n = 4,835), and pregnancy, calving, or weaning status following the first breeding season (PR1, CR1, or WR1, respectively; n = 7,003) from 12 Bos taurus breeds collected at the Meat Animal Research Center (USDA) between 1978 and 1991 were used to estimate genetic parameters. Age at puberty (AP) was defined as age in days at first detected ovulatory estrus. Pregnancy (calving or weaning) status was scored as one for females conceiving (calving or weaning) given exposure during the breeding season and as zero otherwise. The final model for SC included fixed effects of age of dam at breeding (AD), year of breeding (Y), and breed (B) and age in days at measurement as a covariate. Fixed effects in models for AP and AFC were AD, Y, B, and month of birth. Fixed effects in models for PR1, CR1, and WR1 included AD, Y, and B. For all traits, random effects in the model were direct genetic, maternal genetic, maternal permanent environmental, and residual. Analyses for a three-trait animal model were carried out with SC, AP, and a third trait (the third trait was AFC, PR1, CR1, or WR1). A derivative-free restricted maximum likelihood algorithm was used to estimate the (co)variance components. Direct and maternal heritability estimates were 0.41 and 0.05 for SC; 0.16 and 0.03 for AP; 0.08 and 0.00 for AFC; 0.14 and 0.02 for PR1; 0.14 and 0.03 for CR1; and 0.12 and 0.01 for WR1. Genetic correlations between direct and maternal genetic effects within trait were -0.26, -0.63, -0.91, -0.79, -0.66, and -0.85 for SC, AP, AFC, PR1, CR1, and WR1, respectively. Direct genetic correlations between SC and AP and between those traits and AFC, PR1, CR1, and WR1 ranged from -0.15 (between SC and AP) to 0.23 (between AP and WR1). Estimates of heritability indicate that yearling SC should respond to direct selection better than AP, AFC, PR1, CR1, and WR1. Variation due to maternal genetic effects was small for all traits. No strong genetic correlations were detected between SC and female reproductive traits or between AP and the other female traits. These results suggest that genetic response in female reproductive traits through sire selection on yearling SC is not expected to be effective.
Key Words: Beef Cattle • Fertility • Heritability
This article has been cited by other articles:
|
|
 |
|
  J. M. Bormann, L. R. Totir, S. D. Kachman, R. L. Fernando, and D. E. Wilson Pregnancy rate and first-service conception rate in Angus heifers J Anim Sci, August 1, 2006; 84(8): 2022 - 2025. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. G. Kealey, M. D. MacNeil, M. W. Tess, T. W. Geary, and R. A. Bellows Genetic parameter estimates for scrotal circumference and semen characteristics of Line 1 Hereford bulls J Anim Sci, February 1, 2006; 84(2): 283 - 290. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. P. Eler, J. A. I. V. Silva, J. L. Evans, J. B. S. Ferraz, F. Dias, and B. L. Golden Additive genetic relationships between heifer pregnancy and scrotal circumference in Nellore cattle J Anim Sci, September 1, 2004; 82(9): 2519 - 2527. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. DeJarnette, C. E. Marshall, R. W. Lenz, D. R. Monke, W. H. Ayars, and C. G. Sattler Sustaining the Fertility of Artificially Inseminated Dairy Cattle: The Role of the Artificial Insemination Industry J Dairy Sci, July 1, 2004; 87(13_suppl): E93 - 104. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
