Issue |
Genet. Sel. Evol.
Volume 34, Number 4, July-August 2002
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|
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Page(s) | 423 - 445 | |
DOI | https://doi.org/10.1051/gse:2002016 |
Genet. Sel. Evol. 34 (2002) 423-445
DOI: 10.1051/gse:2002016
Modelling the growth curve of Maine-Anjou beef cattle using heteroskedastic random coefficients models
Christèle Robert-Graniéa, Barbara Heudeb and Jean-Louis Foulleyba Station d'amélioration génétique des animaux, Institut national de la recherche agronomique, BP 27, 31326 Castanet-Tolosan, France
b Station de génétique quantitative et appliquée, Institut national de la recherche agronomique, 78352 Jouy-en-Josas Cedex, France
(Received 6 April 2001; accepted 7 January 2002)
Abstract
A heteroskedastic random coefficients model was described for
analyzing weight performances between the 100th and the 650th days of
age of Maine-Anjou beef cattle. This model contained both fixed
effects, random linear regression and heterogeneous variance
components. The objective of this study was to analyze the difference
of growth curves between animals born as twin and single bull calves.
The method was based on log-linear models for residual and individual
variances expressed as functions of explanatory variables. An
expectation-maximization (EM) algorithm was proposed for calculating
restricted maximum likelihood (REML) estimates of the residual and
individual components of variances and covariances. Likelihood ratio
tests were used to assess hypotheses about parameters of this
model. Growth of Maine-Anjou cattle was described by a third order
regression on age for a mean growth curve, two correlated random
effects for the individual variability and independent errors. Three
sources of heterogeneity of residual variances were detected. The
difference of weight performance between bulls born as single and twin
bull calves was estimated to be equal to about 15 kg for the growth
period considered.
Key words: heteroskedastic random coefficient model / EM-REML / robust estimators / growth curve / Maine-Anjou breed
Correspondence and reprints: Christèle Robert-Granié
e-mail: robert@germinal.toulouse.inra.fr
© INRA, EDP Sciences 2002