Background: In national evaluations, direct genomic breeding values can be considered as correlated traits to
those for which phenotypes are available for traditional estimation of breeding values. For this purpose, estimates of
the accuracy of direct genomic breeding values expressed as genetic correlations between traits and their
respective direct genomic breeding values are required.
Methods: We derived direct genomic breeding values for 2239 registered Limousin and 2703 registered Simmental
beef cattle genotyped with either the Illumina BovineSNP50 BeadChip or the Illumina BovineHD BeadChip. For the
264 Simmental animals that were genotyped with the BovineHD BeadChip, genotypes for markers present on the
BovineSNP50 BeadChip were extracted. Deregressed estimated breeding values were used as observations in
weighted analyses that estimated marker effects to derive direct genomic breeding values for each breed. For each
breed, genotyped individuals were clustered into five groups using K-means clustering, with the aim of increasing
within-group and decreasing between-group pedigree relationships. Cross-validation was performed five times for
each breed, using four groups for training and the fifth group for validation. For each trait, we then applied a
weighted bivariate analysis of the direct genomic breeding values of genotyped animals from all five validation sets
and their corresponding deregressed estimated breeding values to estimate variance and covariance components.
Results: After minimizing relationships between training and validation groups, estimated genetic correlations
between each trait and its direct genomic breeding values ranged from 0.39 to 0.76 in Limousin and from 0.29 to
0.65 in Simmental. The efficiency of selection based on direct genomic breeding values relative to selection based
on parent average information ranged from 0.68 to 1.28 in genotyped Limousin and from 0.51 to 1.44 in genotyped
Simmental animals. The efficiencies were higher for 323 non-genotyped young Simmental animals, born after
January 2012, and ranged from 0.60 to 2.04.
Conclusions: Direct genomic breeding values show promise for routine use by Limousin and Simmental breeders
to improve the accuracy of predicted genetic merit of their animals at a young age and increase response to
selection. Benefits from selecting on direct genomic breeding values are greater for breeders who use natural
mating sires in their herds than for those who use artificial insemination sires. Producers with unregistered
commercial Limousin and Simmental cattle could also benefit from being able to identify genetically superior
animals in their herds, an opportunity that has in the past been limited to seed stock animals.