Genomic selection in multi-breed dairy cattle populations

ABSTRACT Genomic selection has been a valuable tool for increasing the rate of genetic improvement in purebred dairy cattle populations. However, there also are many large populations of crossbred dairy cattle in the world, and multi-breed genomic evaluations may be a valuable tool for improving rates of genetic gain in those populations. Multi-breed models are an extension of single-breed genomic models in which a genomic relationship matrix is used to account for the breed origin of alleles in the population, as well as allele frequency differences between breeds. Most studies have found little benefit from multi-breed evaluations for pure breeds that have large reference populations. However, breeds with small reference populations may benefit from inclusion in a multi-breed evaluation without adversely affecting evaluations for purebred performance. Most research has been conducted in taurine breeds, so additional research is needed to determine the value of multi-breed reference populations for composite and synthetic breeds that include both indicine and taurine cattle adapted to tropical climates.