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.