Evolution of inbreeding: a gaze into five Italian beef cattle breeds history

In the last decades, intensive selection programs have led to sustained increases of inbreeding in dairy cattle, a feature that might have adverse consequences on the viability and phenotypic performance of their offspring. This study aimed to determine the evolution of inbreeding of five Italian beef cattle breeds (Marchigiana, Chianina, Romagnola, Maremmana, and Podolica) during a period of almost 20 years (2002-2019). The estimates of Ho, He, F , and F averaged across years (2002-2019) in the studied breeds fluctuated between 0.340-0.401, 0.348-0.392, -0.121-0.072, and 0.000-0.068, respectively. Moreover, annual rates of increase of the estimated inbreeding coefficients have been very low (F = 0.01-0.02%; F = 0.003-0.004%). The use of a high number of bulls combined with strategies implemented by the Association of Italian Beef Cattle Breeders ANABIC to minimize inbreeding might explain these results. Despite the fact that diversity and inbreeding have remained quite stable during the last two decades, we have detected a sustained decrease of the population effective size of these five breeds. Such results should be interpreted with caution due to the inherent difficulty of estimating N_e from SNPs data in a reliable manner.