Better Multi‐Breed Genomic Predictions for Tropical Bull Fertility Using a Breed‐Adjusted Genomic Relationship Matrix

between SHS and PNS which moved from -0.095 ± 0.119 using GRM_u to -0.298 ± 0.113 using GRM_a. For all traits, the correlation between GEBV from GRM_u and GRM_a was > 0.90, indicating similar ranking of animals regardless of the relationship matrix used. However, a random cross-validation scheme showed that using GRM_a increased GEBV accuracies from 0.550 to 0.571 (or 3.7%) for SCC, from 0.496 to 0.509 (or 2.6%) for SHS and from 0.335 to 0.423 (or 26.2%) for PNS. Multi-breed genomic predictions for tropical bull fertility are feasible alternative to individual single-breed evaluation systems. Furthermore, the computational effort required to adjust the genomic relationship matrix for breed-specific allele frequencies is justified by the significant improvement in prediction accuracy, ultimately enhancing the selection of bulls in tropical environments. Collectively these results enable very early in-life selection for bull fertility traits, supporting genetic improvement strategies currently taking place within tropical beef production systems in northern Australia.