Genomic Breed Composition of Selection Signatures in Brangus Beef Cattle

Abstract

Cattle breeding routinely uses crossbreeding between subspecies (Bos taurus taurus and Bos taurus indicus) to form composite breeds, such as Brangus. These composite breeds provide an opportunity to identify recent selection signatures formed in the new population and evaluate the genomic composition of these regions of the genome. Using high-density genotyping, we first identified runs of homozygosity (ROH) and calculated genomic inbreeding. Then, we evaluated the genomic composition of the regions identified as selected (selective sweeps) using a chromosome painting approach. The genomic inbreeding increased at approximately 1% per generation after composite breed formation, showing the need of inbreeding control even in composite breeds. Three selected regions in Brangus were also identified as Angus selection signatures. Two regions (chromosomes 14 and 21) were identified as signatures of selection in Brangus and both founder breeds. Five of the 10 homozygous regions in Brangus were predominantly Angus in origin (probability >80%), and the other five regions had a mixed origin but always with Brahman contributing less than 50%. Therefore, genetic events, such as drift, selection, and complementarity, are likely shaping the genetic composition of founder breeds in specific genomic regions. Such findings highlight a variety of opportunities to better control the selection process and explore heterosis and complementarity at the genomic level in composite breeds.

Estimating inbreeding depression for growth and reproductive traits using pedigree and genomic methods in Argentinean Brangus cattle

“…The mean of the inbreeding coefficients across individuals (F Ped ) was equal to 0.039 with an SD of 0.014, a result that is similar to the one reported by Paim et al (2020) for American Brangus. Pedigree-based inbreeding increased over the years, reaching an average value of 4% in 2019 (Figure 2).…”

Food Resources Biodiversity: The Case of Local Cattle in Slovakia

“…Obtained results confirmed the tested assumption that the different production type of analysed breeds could cause an increase in the frequency of specific alleles (haplotypes) responsible for desired phenotypic traits. The strong impact of selection on the genomic region related to carcass traits in beef cattle was also reported by Moravčíková et al [88], Jahuey-Martínez et al [89] or Paim et al [90]. In dairy cattle, the most significant selection signatures were found mainly on chromosome 6 that is strongly connected to milk production and composition [91,92].…”

Taurine and Indicine Haplotype Representation in Advanced Generation Individuals From Three American Breeds

“…These windows were among the 5 most differentiated windows for Brahman genome content in both breeds (Table 4). Paim et al (2020b) found evidence of strong enrichment of Angus alleles at Polled in 59 Brangus animals, but not at MC1R. Ancestral breed frequency signatures on chromosome 5 are impacted by a very strongly selected locus enriched in frequency for Brahman alleles in all three of the American Breeds towards the center of the chromosome (Figures 1-3).…”