Comparing pedigree and genomic relationships to control inbreeding in optimum-contribution selection restricting the number of sires in pigs

Introduction Pedigree relationships to control inbreeding in optimum-contribution selection (POCS) realised a higher rate of true genetic gain (ΔG) than use of genomic relationships for optimum-contribution selection (GOCS) at the same rate of true inbreeding (ΔF) (Henryon et al., 2019). Recently, Gautason et al. (2022) found that GOCS realised just as much ΔG as POCS but at lower ΔF when they fixed the number of selected sires in their simulations of a breeding scheme for dairy cattle. The striking difference with the study of Gautason et al. (2022) is that they restricted ΔF in POCS and GOCS to the same rate but did so on different scales based either on pedigree or genomic information. However, if DF based on the same scale in POCS and GOCS is compared at the same ΔG, POCS realises less ΔF by allocating matings to more sires and dams from more full-sib families than GOCS. This suggests that POCS may not be as good as GOCS when the number of sires and dams allocated to matings is fixed. Based on this information, it was hypothesised that GOCS would realise less ΔF at the same ΔG than POCS when number of sires and dams allocated to matings is fixed.