Heterogeneity of variance for type traits in the Montbeliarde cattle breed

C Robert-Granié, V Ducrocq, JL Foulley
1997 Genetics Selection Evolution  
This paper presents and discusses the estimation of genetic and residual (co-) variance components for conformation traits recorded in different environments using mixed linear models. Testing procedures for genetic parameters (genetic correlations between environments constant or equal to one, genetic correlation equal to one and constant intra-class correlations, homogeneity of variance-covariance components) are presented. These hypotheses were described via heteroskedastic univariate sire
more » ... c univariate sire models taking into account genotype x environment interaction. An expectation-maximization (EM) algorithm was proposed for calculating restricted maximum likelihood (REML) estimates of the residual and genetic components of variances and co-variances. Likelihood ratio tests were suggested to assess hypotheses concerning genetic parameters. The procedures presented in the paper were used to analyze and to detect sources of variation on conformation traits in the Montbeliarde cattle breed using 24 301 progeny records of 528 sires. On all variables analyzed, several sources (stage of lactation, classifiers, type of housing) of heterogeneity of residual and genetic variances were clearly highlighted, but morphologie de 24 301 performances d'animau! de race Montbéliarde issus de 528 pères. Sur l'ensemble des variables analysées, différentes sources (stade de lactation, pointeurs, type de logement) d'hétérogénéité des variances génétiques et résiduelles ont été mises en évidence mais en général L'héritabilité du caractère reste constante d'un milieu à l'autre. hétéroscédasticité / modèles mixtes / interaction génotype X milieu / algorithme EM / estimation REML
doi:10.1186/1297-9686-29-5-545 fatcat:nvip3pobrnb5bo6mszvpm5cl5e