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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #419651
Research Project: Identifying and Mitigating Factors that Limit Beef Production Efficiency

Location: Livestock and Range Research Laboratory

Title: Out of Africa: Genetic characterization and diversity of Mashona cattle in the United States

Author
item Ling, Ashley
item Hay, El Hamidi
item Lozada-Soto, Emmanuel
item HAYES, EMILY - Tennessee State University
item BROWNING, RICHARD - Tennessee State University
item Blackburn, Harvey

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2025
Publication Date: 2/14/2025
Citation: Ling, A.S., Hay, E.A., Lozada-Soto, E.A., Hayes, E., Browning, R., Blackburn, H.D. 2025. Out of Africa: Genetic characterization and diversity of Mashona cattle in the United States. Journal of Animal Science. https://doi.org/10.1093/jas/skaf045.
DOI: https://doi.org/10.1093/jas/skaf045

Interpretive Summary: The Mashona cattle, a Bos taurus and Bos indicus composite, were brought from Zimbabwe to New Mexico in the 1990s. Since then, they have been valued by ranchers in hot and humid areas for their resistance to pests, heat and maternal characteristics, making them ideal for crossbreeding. This study aimed to explore the genetic background and diversity of Mashona cattle in the U.S. by analyzing 24 samples from Tennessee State University. These were compared to other cattle breeds, including Angus, Brahman, and Tuli. The analysis used advanced genomic techniques to understand the genetic variation and historical lineage. Results showed that Mashona cattle have a high proportion of Bos taurus genes (about 81%). They also form a distinct genetic group along with the Tuli breed, indicating unique diversity in Sanga breeds. Some genes identified in Mashona cattle were associated with traits like horn fly resistance and maternal characteristics. Despite their genetic strengths, the Mashona have a small population size, which requires careful management to maintain their genetic diversity while selecting for desired traits.

Technical Abstract: Mashona is a Sanga breed believed to be an ancient Bos taurus and Bos indicus composite. Since importation producers with relatively small herds (<70 cows per herd) and located in hot-humid regions have found them useful in crossbreeding programs due to purported resistance to pests and heat stress. This study evaluated the genomic composition of US Mashona to better understand their population history and determine level of genetic diversity. Twenty-four Mashona from Tennessee State University were sampled and genotyped. A reference population of Bos taurus (Angus, Hereford, Wagyu, Romosinuano, and Florida Cracker) and Bos indicus (Brahman) breeds, as well as from an additional Sanga breed (Tuli) was obtained from the USDA-ARS gene bank. All individuals were genotyped using the 777k Illumina BovineHD panel. Genomic diversity across breeds was evaluated using measures of genetic distance, allelic frequency, inbreeding, and admixture analyses. The first four principal components explained 15.5, 4.3, 3.1, and 2.4% of the genetic variation in the genotyped animals. Mashona and Tuli were distinct but tended to cluster near one another for all principal components, particularly along the 4th principal component (variation along European-African axis). The ADMIXTURE analysis revealed that the average proportion of Bos taurus genetics in Mashona was 0.81, with individual proportions ranging from 0.77 to 0.84. Additionally, the unsupervised ADMIXTURE analysis indicated that Mashona and Tuli form a distinct ancestry group, suggesting that Sanga breeds possess unique genetic diversity compared to the other breeds evaluated in this study. Examining regions with high autozygosity or differentiated from other breeds revealed several selection signatures in the Mashona population. An ROH region on chromosome 6 contained genes associated with horn fly resistance. Additional ROH regions contained genes and QTLs associated with calving ease, reproduction and maternal traits. Fixation index analysis of pairwise SNP between Mashona Angus, Brahman, and Tuli breeds uncovered several genomic regions exhibiting high differentiation. Historical trends in Mashona effective population size (Ne = 28) align with known past demographic events and indicated a narrowing of its genetic base. With insights into Mashona’s unique level of genetic diversity but its relatively small population size; breeders will need to balance existing genetic diversity and selection for important traits.