IcelandEnvironmentGene-Environment InteractionGenetic Predisposition to DiseaseGenotypeRisk FactorsBreedingPanicumQuantitative Trait, HeritableWeaningModels, GeneticTwin Studies as TopicGenetic PleiotropyHybrid VigorSocial EnvironmentQuantitative Trait LociPhenotypeAnimal HusbandryCrosses, GeneticReceptors, Dopamine D4PoaceaeSelection, GeneticEpistasis, GeneticDiseases in TwinsCattleSerotonin Plasma Membrane Transport ProteinsGenetic VariationTwinsBody WeightAllelesChromosome MappingTriticumPolymorphism, Single NucleotideSeasonsLife Change EventsModels, StatisticalAnalysis of VarianceRegression AnalysisReproductionAnimal FeedLinear ModelsGenetic MarkersPolymorphism, GeneticModels, BiologicalMolecular Sequence Data