Changes in the relationship between an endangered cattle breed and its mainstream sister breed over time

Because of lack of pedigree records, the history of the Red-Pied of the Ösling (RPO) breed, which is an endangered local red-pied cattle breed from Luxembourg, is not really known. However, it is assumed that there has been exchanges between the RPO and the Meuse-Rhine-Yssel (MRY), another red-pied cattle breed from The Netherlands. To validate this assumption, we estimated the changes in the relationships between the RPO and MRY breeds over time by the definition of cohorts with different birthdates in the MRY breed. The fixation indexes between the RPO breed and the different MRY cohorts, as well as a principal component analysis, showed that the RPO breed was more related to the oldest MRY animals, born before 1990, and to the youngest MRY animals, born after 2009. This confirmed the a priori known pattern of importation of MRY animals to the RPO population over time. Based on results obtained in a genomic relationship matrix and on the proportion of opposing homozygotes, we could infer sire-offspring relationships between an MRY sire and three RPO animals. To complete the pedigree of RPO animals even further and optimize exchanges between the MRY and RPO breeds, it would be interesting to have access to more MRY genotypes.