title: Modelling and estimation of genotype by environment interactions for production traits in French dairy cattle.
abstract: BACKGROUND
  Genotype by environment interactions are currently ignored in national genetic evaluations of dairy cattle. However, this is often questioned, especially when environment or herd management is wide-ranging. The aim of this study was to assess genotype by environment interactions for production traits (milk, protein, fat yields and fat and protein contents) in French dairy cattle using an original approach to characterize the environments.
  
  
  METHODS
  Genetic parameters of production traits were estimated for three breeds (Holstein, Normande and Montbéliarde) using multiple-trait and reaction norm models. Variables derived from Herd Test Day profiles obtained after a test day model evaluation were used to define herd environment.
  
  
  RESULTS
  Multiple-trait and reaction norm models gave similar results. Genetic correlations were very close to unity for all traits, except between some extreme environments. However, a relatively wide range of heritabilities by trait and breed was found across environments. This was more the case for milk, protein and fat yields than for protein and fat contents.
  
  
  CONCLUSIONS
  No real reranking of animals was observed across environments. However, a significant scale effect exists: the more intensive the herd management for milk yield, the larger the heritability.
authors.affiliation: INRA, UMR1313 Génétique Animale et Biologie Intégrative, F-78352 Jouy-en-Josas, France.
authors.forename: Bérénice
authors.initials: B
authors.lastname: Huquet
authors.forename: Hélène
authors.initials: H
authors.lastname: Leclerc
authors.forename: Vincent
authors.initials: V
authors.lastname: Ducrocq
mesh_terms: D000818:Animals; D017849:Animals, Inbred Strains / Q000235:genetics; D002417:Cattle / Q000235:genetics*; D003612:Dairying / Q000379:methods; D005602:France; D059647:Gene-Environment Interaction; D005838:Genotype; D008957:Models, Genetic; D015233:Models, Statistical; D019655:Quantitative Trait, Heritable