Genomic structure and selection history across Angus populations worldwide: insights from ROH, selection mapping, and functional analyses

Angus cattle, originally from Scotland, have been selectively bred for over 400 years, making them one of the most prominent beef breeds globally. Known for their adaptability, natural polled traits, and high-quality beef, Angus cattle have been intensively selected for growth, body size, and feed efficiency. This study investigates the genetic diversity, selection history, and key genomic regions across five Angus populations from the USA, Canada, Australia, Brazil, and Red Angus of America. Genomic data from 71,283 animals born between 1961 and 2024 were analyzed using Principal Component Analysis (PCA), phylogenetic tree construction, and Runs of Homozygosity (ROH), with the Generation Proxy Selection Mapping (GPSM) approach used to assess selection history. Functional annotation identified candidate genes and pathways related to selection. Our analysis revealed both similarities and differences across populations. The PCA and FST metrics showed minimal differentiation between the American, Canadian, Australian, and Brazilian populations, with greater differentiation observed in the Red Angus population. The ROH analysis revealed that the Brazilian population had the highest number of ROHs. The ROH islands identified on BTA8 and BTA13 in the American and Australian populations were linked to traits like body weight, marbling, and tenderness. The GPSM identified significant markers associated with body weight and growth in all populations, reflecting ongoing selection pressures. This study highlights the potential of genomics to improve our understanding of Angus cattle's genetic architecture and selection history. It underscores the feasibility of integrating global populations for more accurate genomic evaluations, enhancing genetic predictions, and supporting sustainable beef production worldwide.