Dairy cattle genomics: Tools to accelerate genetic improvement?

Traditional selection based on genetic merit calculated from phenotypic and pedigree information has been tremendously effective at improving production in dairy cattle. Hypothetically, genetic improvement could be accelerated even further for yield and other economically important traits by directly selecting upon the genetic differences underlying the phenotypes. To elucidate these genetic differences, research strategies based on genomic science have been developed to identify economic trait loci (ETL). Once resolved with respect to position in the genome, DNA markerbased tests that identify ETL can be practically applied to enhance selection in a commercial setting. To date, most dairy-related ETL have been detected in Holstein grandsire families using the granddaughter design. Because the marker intervals identifying these ETL are not resolved well enough for accurate selection in current populations, ETL analyses have been or are being extended to include ancestral animals that connect family pedigrees and current generations of nonprogenytested animals from within the founder animal pedigree. Increasing genotypic and phenotypic information