HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: jas.2008-1442v1 87/5/1628    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Williams, J. L. Articles by Speidel, S. E. Search for Related Content PubMed PubMed Citation Articles by Williams, J. L. Articles by Speidel, S. E.

Reducing bias in maintenance energy expected progeny difference by accounting for selection on weaning and yearling weights¹

J. L. Williams^*, D. J. Garrick^*,,,2 and S. E. Speidel^*

^* Department of Animal Sciences, Colorado State University, Fort Collins 80523-1171; and Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand; and Department of Animal Science, Iowa State University, Ames 50011

² Corresponding author: dorian{at}iastate.edu

Maintenance energy requirements of cattle can be predicted from published equations utilizing metabolic BW and milk production potential. Metabolic BW is a function of BW at a constant fat percentage or BCS. Pedigree and performance records can be used in random regression models to predict genetic merit for metabolic BW and milk production potentials. The purpose of this study was to present a methodology for predicting mature cow maintenance energy EPD using mature cow BW and BCS and accounting for prior selection of replacement females at weaning and yearling ages. Variance components were obtained for direct and maternal effects on weaning weight, direct effects on postweaning BW gain, and direct coefficients for random regression on mature weights (MW) adjusted for BCS. These BW were transformed into metabolic BW by taking BW to the power of 0.75, variance components were estimated for metabolic BW, and were then used to predict breeding values from which cow maintenance energy EPD could be derived. Data used in this analysis were obtained from the Red Angus Association of America and limited to herds with MW and corresponding BCS observations. The data set included 52,338 BW records on 21,103 individuals. Weaning and yearling contemporaries to those with MW observations, but with no MW records themselves, were included to account for selection occurring before maturity. Heritability estimates for weaning weight direct, weaning weight maternal, and postweaning BW gain were 0.18 ± 0.02, 0.16 ± 0.02, and 0.18 ± 0.02, respectively. Mature BW observed at 2, 3, 4, 5, and 6 yr of age had heritability estimates of 0.45 ± 0.03, 0.44 ± 0.03, 0.49 ± 0.03, 0.66 ± 0.04, and 0.62 ± 0.05, respectively. Correlations between weaning weight direct and MW ranged from 0.65 ± 0.07 to 0.82 ± 0.04, and correlations between MW at different ages ranged from 0.95 ± 0.03 to 0.99 ± 0.01. The genetic correlations between postweaning BW gain and MW ranged from 0.48 ± 0.06 to 0.59 ± 0.06. The 15-yr genetic increase in metabolic BW was 3.6 kg^0.75, greater than the value of 0.23 kg^0.75 obtained from the same data ignoring weaning and yearling contemporaries with unobserved MW, the approach currently used in the derivation of cow maintenance EPD published by the Red Angus Association of America.

Key Words: beef cattle • maintenance energy • mature body weight • random regression