Abstract
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, 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, annual rates of increase of the estimated inbreeding coefficients have 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 results should be interpreted with caution due to the inherent difficulty of estimating Ne from SNPs data in a reliable manner.
Highlights
Inbreeding is the main consequence of mating individuals that are related, through common ancestry, to a degree that exceeds that of two individuals from the same population extracted at random (Kardos et al, 2016)
The removal of genotyped animals with pedigree completeness index (PCI) less than 90% resulted in the exclusion of less than 1.5% of the sample, as most of the genotyped animals had PCI greater than 90%
The low level of inbreeding found in this study confirms the success of the Italian beef cattle selection program carried out by ANABIC, which aimed to minimize inbreeding
Summary
Inbreeding is the main consequence of mating individuals that are related, through common ancestry, to a degree that exceeds that of two individuals from the same population extracted at random (Kardos et al, 2016). One key advantage of this latter approach is that it captures ancient inbreeding accumulated in the base population and it is less affected by parentage errors (Howard et al, 2017). Several studies (Bjelland et al, 2013; Pryce et al, 2014) have revealed the distortion caused by ancient contributions to inbreeding dilutes up to a degree in which pedigree-based analyses and genomic analyses may not differ that much
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