Genome-wide association study was carried out in Nordic Holsteins, Nordic Red and Jersey breeds for functional traits using BovineHD Genotyping BreadChip (Illumina, San Diego, CA). The association analyses were carried out using both linear mixed model approach and a Bayesian variable selection method. Principal components were used to account for population structure. The QTL segregating in all three breeds were selected and a few of the most significant ones were followed in further analyses. The polymorphisms in the identified QTL regions were imputed using 90 whole genome sequences available from these three breeds. Imputations were done using IMPUTE v2.2. Association analyses with imputed polymorphisms were repeated for the targeted regions. The QTL genotypes of the sires with more than 20 sons were determined by an a posteriori granddaughter design. The concordance of sires for putative quantitative trait nucleotide was determined.