The genomic inbreeding trend over the last 25 years in three Italian pig breeds

Inbreeding is an important parameter that should be monitored in livestock populations under selection. The traditional inbreeding coefficient (FPED) is based on pedigree data. Runs of homozygosity (ROH) can be used to define one of the most accurate genomic inbreeding parameters, defined as the proportion of the autosomal genome covered with ROH (FROH). The aim of this work was to evaluate how 25 years of selection have shaped the inbreeding level of the three heavy pig breeds raised in Italy: Italian Large White, Italian Landrace and Italian Duroc. For all breeds, the average FROH increased over time, as expected in populations under selection. What was interesting is that the rate of inbreeding was higher for FPED than for FROH. This might mean that the rate of inbreeding could be overestimated by using only pedigree information. FROH can complement traditional FPED coefficient to monitor inbreeding in these populations.