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Research Project: National Animal Germplasm Program

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Title: Genetic structure of Angus and Salers in relation to SNP associated with pulmonary arterial pressure

item Blackburn, Harvey
item Krehbiel, Bethany
item THOMAS, MILTON - Colorado State University
item SPEIDEL, SCOTT - Colorado State University
item ENNS, MARK - Colorado State University

Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/28/2017
Publication Date: 8/1/2017
Citation: Blackburn, H.D., Krehbiel, B.C., Thomas, M., Speidel, S., Enns, M.R. 2017. Genetic structure of Angus and Salers in relation to SNP associated with pulmonary arterial pressure. Journal of Animal Science.

Interpretive Summary:

Technical Abstract: Cattle living in the Rocky Mountains (elevations > 1,500 m) are often at risk of contracting high altitude disease. Low atmospheric pressure at high altitudes causes pulmonary hypertension and potentially right heart failure. Pulmonary arterial pressure (PAP) is an indicator for pulmonary hypertension. PAP measurements of < 41 mmHg are categorized as low risk for the development of pulmonary hypertension at high altitudes. Genetic resilience to the disease is possible and can be achieved through breed or within breed selection. Here we explored differences between Angus raised at 2,150 m divided into low (< 41 mmHg; n = 24) and high PAP (> 41 mmHg; n = 41) groups and Salers (n = 24) at loci associated with PAP. The Salers sampled, a French mountainous breed (< 4,800 m elevation), were all full blood. The mean Angus PAP score was 49 ± 2.1 mmHg (range 35 to 115). To determine the population structure between the two breeds, 121,756 SNP pruned from the 777,972 SNP on BovineHD beadchip were evaluated using Admixture to infer ancestral populations. Previously identified SNP (n = 40) associated with PAP in Angus cattle through genome-wide association studies were used to assess genetic diversity of both breeds. Chi-square tests were performed to identify statistical differences among the allele frequencies among the breed groups. We used TreeSelect to identify allele frequency divergence from a central node due to selection. Admixture revealed by the lowest-cross validation error that two distinct populations existed. Chi-square tests of SNP genotypic frequencies among the groups revealed that 23 of the 40 SNP differed (P < 0.025). Sixteen SNP differed between both low and high PAP Angus groups versus Salers. These results show the high PAP Angus genotypic frequencies differentiated themselves from the low PAP Angus genotypic frequencies. However, both high and low PAP Angus group allele frequencies showed evidence of approaching the frequencies observed in Salers. TreeSelect identified four SNP under selection. Of those SNP, three SNP allele frequencies were similar between low PAP Angus and Salers. These results indicate genetic diversity exists between Angus and Salers cattle. However, given that high altitude disease is a polygenic trait, there is evidence of allele frequency similarities of low PAP Angus and Salers, which suggests that selection for high altitude tolerance is achievable, but also that breed choice can play an important role in producing livestock in harsh environmental conditions.