Inbreeding trends in five Italian beef cattle breeds: a perspective of almost two decades (2002-2020)

In the last decades, intensive selection programs have led to sustained increases of inbreeding in dairy cattle, a feature which might have adverse consequences on the viability and phenotypic performance of their offspring. The aim of this study was to determine the evolution of inbreeding of the 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, Fhat2, and Fped 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, the annual rate of increase of the estimated inbreeding coefficients has been very low (Fhat2 = 0.01 - 0.02 %; Fped = 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 result should be interpreted with caution due to the inherent difficulty of estimating Ne from SNPs data in a reliable manner.