Conservation & local programs

Exploring genetic diversity of the Angus population: a temporal multi-country perspective

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Abstract

The advent of frozen semen and artificial insemination technologies decreased the geographical limitations for genetic selection. This genetic exchange across countries may increase the rate of genetic progress but could also impact genetic diversity over time. The objective of this study was to identify country-level trends in the genetic diversity of the Angus breed across United States (USA), Canada, and Australia. The population used for the analysis consisted of animals included in the World Angus Evaluation (WAE), which encompasses populations from all three countries. Pedigree included 15,878,206 animals born between 1887 and 2025, of which 1,300,000 were genotyped and imputed to a common set. USA, Australian and Canadian populations represented 76.04%, 13.06%, and 9.78% of the pedigree analyzed, respectively. Measures of genetic diversity such as effective number of founders and ancestors, marginal genetic contribution to inbreeding, pedigree and genomic inbreeding, and genetic diversity as percentage were obtained. The analysis was performed within country and over the years based on the animals' birth year, starting from 1975 to 2024. Our results indicate a decrease in genetic variability over time which can be expected as these populations have been under selection. Pedigree inbreeding increased from 0.01 to 0.05 for Australia, 0.02 to 0.06 for USA, and from 0.01 to 0.03 for Canada. Between 1975 and 2024, the marginal contribution analyses showed that the marginal contribution of the top ten animals with higher probability of gene origin increased by 2.1, 3.0 and 4.5 times the initial contribution for Canada, USA and Australia, respectively. Overall, the effective number of ancestors decreased for the three populations, with a more accelerated reduction for Australia between 1976 and 1995. The maximum contribution of nodal common ancestors to inbreeding indicated the use of similar genetics for multiple years and across countries. This highlights the international exchange of genetic material over the years. Our results showed that the Canadian population maintained a lower level of inbreeding, and higher number of effective ancestors compared to the Australian and USA populations. The Australian population shares similar variability indicators with USA, albeit having a smaller population and different indicators in the early years of the pedigree analyzed. Results for genetic diversity indicated genetic drift as source for decreased variability. This study highlights the increased use of shared genetics across countries in recent years, and a rising level of inbreeding. Our study shows the importance of monitoring genetic variability indicators both within populations and at a global level. The results obtained emphasize the relevance of cross-country genetic evaluations, such as the WAE, when there is significant sharing of genetics globally, to broaden the choices for genetic selection, and to monitor and sustain genetic variability in balance with genetic gain.

Keywords: 2026

How to Cite:

Novo, L., Medeiros, R., Garcia, A., Ramos, P., Latimer, K., Samaraweera, M., Teseling, C. & Retallick-Riley, K., (2026) “Exploring genetic diversity of the Angus population: a temporal multi-country perspective”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286716. doi: https://doi.org/10.31274/wcgalp.24102

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