Insights into Genetic Diversity, Runs of Homozygosity and Heterozygosity-Rich Regions in Maremmana Semi-Feral Cattle Using Pedigree and Genomic Data

Abstract

Semi-feral local livestock populations, like Maremmana cattle, are the object of renewed interest for the conservation of biological diversity and the preservation and exploitation of unique and potentially relevant genetic material. The aim of this study was to estimate genetic diversity parameters in semi-feral Maremmana cattle using both pedigree- and genomic-based approaches (FIS and FROH), and to detect regions of homozygosity (ROH) and heterozygosity (ROHet) in the genome. The average heterozygosity estimates were in the range reported for other cattle breeds (HE=0.261, HO=0.274). Pedigree-based average inbreeding (F) was estimated at 4.9%. The correlation was low between F and genomic-based approaches (r=0.03 with FIS, r=0.21 with FROH), while it was higher between FIS and FROH (r=0.78). The low correlation between F and FROH coefficients may be the result of the limited pedigree depth available for the animals involved in this study. The ROH islands identified in Maremmana cattle included candidate genes associated with climate adaptation, carcass traits or the regulation of body weight, fat and energy metabolism. The ROHet islands contained candidate genes associated with nematode resistance and reproduction traits in livestock. The results of this study confirm that genome-based measures like FROH may be useful estimators of individual autozygosity, and may provide insights on pedigree-based inbreeding estimates in cases when animals’ pedigree data are unavailable, thus providing a more detailed picture of the genetic diversity.

Keywords

• maremmana cattle
• runs of homozygosity
• inbreeding
• heterozygosity-rich regions
• pedigree relationships
• genomic relationships