title: Genomic prediction of unordered categorical traits: an application to subpopulation assignment in German Warmblood horses.
abstract: BACKGROUND
  Categorical traits without ordinal representation of classes do not qualify for threshold models. Alternatively, the multinomial problem can be assessed by a sequence of independent binary contrasts using schemes such as one-vs-all or one-vs-one. Class probabilities can be arrived at by normalization or pair-wise coupling strategies. We assessed the predictive ability of whole-genome regression models and support vector machines for the classification of horses into four German Warmblood breeds.
  
  
  RESULTS
  Prediction accuracies of leave-one-out cross-validation were high and ranged from 0.75 to 0.97 depending on the binary classifier and breeds incorporated in the training. An analysis of the population structure using eigenvectors of the genomic relationship matrix revealed clustering of individuals beyond the given breed labels. Admixture between two breeds became apparent which had substantial impact on the prediction accuracies between those two breeds and also influenced the contrasts between other breeds.
  
  
  CONCLUSIONS
  Genomic prediction of unordered categorical traits was successfully applied to subpopulation assignment of German Warmblood horses. The applied methodology is a straightforward extension of existing binary threshold models for genomic prediction.
authors: Institute of Animal Breeding and Husbandry, University of Kiel, Hermann-Rodewald-Strasse 6, 24098, Kiel, Germany. cheuer@tierzucht.uni-kiel.de.
authors: Claas
authors: C
authors: Heuer
authors: Institute of Animal Breeding and Husbandry, University of Kiel, Hermann-Rodewald-Strasse 6, 24098, Kiel, Germany. cscheel@tierzucht.uni-kiel.de.
authors: Christoph
authors: C
authors: Scheel
authors: Institute of Animal Breeding and Husbandry, University of Kiel, Hermann-Rodewald-Strasse 6, 24098, Kiel, Germany. jtetens@tierzucht.uni-kiel.de.
authors: Jens
authors: J
authors: Tetens
authors: Institute for Genome Biology, Leibniz Institute for Farm Animal Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany. kuehn@fbn-dummerstorf.de.|Faculty of Agricultural and Environmental Sciences, University Rostock, Justus-von-Liebig-Weg 6, 18059, Rostock, Germany. kuehn@fbn-dummerstorf.de.
authors: Christa
authors: C
authors: Kühn
authors: Institute of Animal Breeding and Husbandry, University of Kiel, Hermann-Rodewald-Strasse 6, 24098, Kiel, Germany. gthaller@tierzucht.uni-kiel.de.
authors: Georg
authors: G
authors: Thaller
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D001947:Breeding; D005828:Genetics, Population; D016678:Genome; D023281:Genomics / Q000379:methods*; D005838:Genotype; D005858:Germany; D006736:Horses / Q000235:genetics*; D008957:Models, Genetic; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D019655:Quantitative Trait, Heritable; D012044:Regression Analysis; D060388:Support Vector Machine