Prior to 2019, crossbred animals could not receive genomic predictions, because the evaluations are based on the purebred reference populations. With this enhancement, genomic evaluations are now available for more U.S. dairy animals. This enables all genotyped animals to receive the best possible estimate of their genetic value, regardless of the animals’ breed composition. This increases the value of genotyping for dairy producers, especially when applied across the whole herd.
Evaluations for crossbred animals resulted from a well-researched, complex development process and collaboration between USDA, CDCB and other U.S. partners The foundation was set in 2007, with the implementation of an all-breed evaluation system for traditional U.S. evaluations. In 2016, the U.S. published values for Breed Base Representation (BBR) values – currently only provided through the U.S. system. BBR is an estimate of the percentage of DNA contributed to an individual animal by each of the 5 primary U.S. dairy breeds with a genomic evaluation (Holstein, Jersey, Ayrshire, Brown Swiss, and Guernsey).
In April 2018, the calculation of genomic evaluations changed to the all-breed base used for traditional evaluations since 2007. This allowed genomic evaluations to be combined accurately across breeds.
The breed composition of the U.S. dairy herd has changed significantly from 1990 to 2018, accordingly to Dairy Herd Information data. One notable shift is the increase in crossbred dairy cows, meaning the animal’s sire and dam are of different breeds. About 5% of all cows in U.S. herds on DHI test were of crossbred parentage in 2018, compared to 0.1% in 1990.
U.S. producers that use a crossbreeding strategy have diverse reasons, like shifting demand for dairy products and milk composition attributes, renewed interest in different traits, and desire to capitalize on heterosis.