IcelandEnvironmentGene-Environment InteractionGenetic Predisposition to DiseaseGenotypeRisk FactorsBreedingPanicumQuantitative Trait, HeritableWeaningModels, GeneticTwin Studies as TopicGenetic PleiotropyQuantitative Trait LociHybrid VigorSocial EnvironmentPhenotypeCrosses, GeneticAnimal HusbandryReceptors, Dopamine D4PoaceaeSelection, GeneticEpistasis, GeneticDiseases in TwinsGenetic VariationSerotonin Plasma Membrane Transport ProteinsCattleTwinsBody WeightAllelesChromosome MappingPolymorphism, Single NucleotideTriticumSeasonsModels, StatisticalGenetic MarkersAnalysis of VarianceLife Change EventsRegression AnalysisPolymorphism, GeneticReproductionAnimal FeedLinear ModelsModels, BiologicalMolecular Sequence Data