Inbreeding depression due to recent and ancient inbreeding in Dutch Holstein–Friesian dairy cattle

Background Inbreeding decreases animal performance (inbreeding depression), but not all inbreeding is expected to be equally harmful. Recent inbreeding is expected to be more harmful than ancient inbreeding, because selection decreases the frequency of deleterious alleles over time. Selection efficiency is increased by inbreeding, a process called purging. Our objective was to investigate effects of recent and ancient inbreeding on yield, fertility and udder health traits in Dutch Holstein–Friesian cows. Methods In total, 38,792 first-parity cows were included. Pedigree inbreeding ( F_PED ) was computed and 75 k genotype data were used to compute genomic inbreeding, among others based on regions of homozygosity (ROH) in the genome ( F_ROH ). Results Inbreeding depression was observed, e.g. a 1