Genomic selection refers to decisions based on genomic breeding values. Genomic selection builds on a solid foundation of phenotypic and genomic data collection and advanced evaluation methods. Genomic evaluations are computed based on analyses of animals’ DNA, genetic markers on the bovine genome and comparison with a breed-specific reference population.
Genomic selection leads to remarkable genetic progress due to a shortened generation interval, increased selection accuracy (reliability) and increased selection intensity for males and females as parents of the next generation.
Genomic selection in U.S. Holsteins has doubled the annual rates of genetic gain for production traits. For fitness traits, like fertility, health and productive life, the genetic gain has proven even higher.
At A.I. centers, the breeding programs and semen production rapidly transformed when genomic evaluations became available. Higher reliabilities of genomic evaluations resulted in semen becoming readily available on young sires marketed only on their genomic predictions, with no milking daughters. A.I. organizations and breeders were able to accurately identify genetically-elite parents of the next generation – both male and female – at a very young age.
U.S. dairy producers embraced the genetic potential of younger sires. By 2021, young genomic sires accounted for 71% of the inseminations in U.S. herds that record through Dairy Herd Information (DHI). In addition to genomic testing of elite females for marketing, commercial herds adopted genotyping as an additional and vital tool for mating, culling and herd management decisions.
There are many traits that are critically important yet difficult and expensive to measure. Genomics has reduced the need for many phenotypes, thereby allowing measurement for these challenging traits. Phenotypes can be collected on a small, strategically-chosen group of genotyped animals. Marker effects can then be calculated based on the reference population and used to predict genomic breeding values for the entire population, including animals without any measured phenotypes.
In April 2018, CDCB launched genomic evaluations for six disease resistance traits. In December 2020, Feed Saved was introduced as a new tool to predict feed efficiency of individual animals, enable producers to save on feed costs and help reduce dairy’s environmental footprint.
Researchers at the U.S. Department of Agriculture and other institutions began investigating genomic scans and genetic markers in the 1990s. By the early 2000s, the U.S. dairy organizations were preparing to implement genomic selection into genetic development at A.I. centers and herd management strategies on farms.
The U.S. genotypic database has grown rapidly as genomic testing has been adopted within dairy herds. One million animal genotypes are submitted annually to CDCB – with 91% of those being females. By breed, 86% of all genotypes are Holstein and 12% are Jersey.