Conservation & local programs

Estimated proportions of Bos taurus and Bos indicus admixture in Mashona and Tuli, ancient composites from Zimbabwe

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Abstract

Mashona is a Sanga-type breed believed to be an ancient Bos taurus (BT) and Bos indicus (BI) composite. Mashona, imported to the US from Zimbabwe in the 1990s, have found popularity in hot-humid regions of the US due to purported heat and pest resistance. This analysis sought to estimate proportions of BT and BI ancestry in the present-day genome of US Mashona to seek a better understanding of their population history and elucidate the effect of long-term composite development on the genome. Genotypes were obtained for 24 Mashona owned and managed by Tennessee State University. A reference population of BT (Angus, Hereford, Wagyu, Romosinuano, and Florida Cracker) and BI (Brahman) breeds was obtained from the USDA-ARS National Animal Germplasm Program (NAGP). Mashona were compared to Tuli, another Sanga breed, and Brangus, a more recent BT and BI composite. All individuals were genotyped using the 777k Illumina BovineHD BeadChip. Proportions of BT and BI admixture in Mashona were estimated using a supervised implementation of the ADMIXTURE program with two historical populations (k=2) representing BT and BI ancestry. The training sets for each historical population were composed of a random sample of n=50 genotypes from the appropriate breeds and individuals in the training set were assumed to have 100% membership with their assigned historical population (no admixture). The procedure to randomly sample individuals for training and estimate admixture was repeated across 100 iterations in a bootstrap approach such that every individual from non-composite breeds entered the training set at least once and each individual in the analysis had admixture estimated as part of the validation population multiple times. Admixture was estimated for the collective genome as well as individual chromosomes. The mean estimated BT composition for Mashona was 0.81 and ranged between 0.77 and 0.84 across individuals. Comparatively, the mean estimated BT composition among the reference breeds was 0.04 (Brahman), 0.93 (Florida Cracker), 0.94 (Romosinuano), 0.96 (Angus), 0.97 (Wagyu), and 0.98 (Hereford). Estimated BT composition for Tuli was similar to Mashona at 0.81. Brangus BT composition was estimated at 0.64, close to the expected proportion of 5/8 Angus admixture. Mashona showed large variation in estimated BT composition of individual chromosomes, ranging from 0.61 for chromosome 26 to 0.95 for chromosome 25. This variation may indicate differential selection pressure for BT and BI genetics across different chromosomes. Tuli showed a similar distribution of BT composition across chromosomes but with less variation, ranging from 0.71 for chromosome 7 to 0.9 for chromosome 25. Results support that Mashona, along with Tuli, may be ancient composites of BT and BI and that signatures of this admixture persist in the modern-day genome. These results may have implications on long-term development of composite breeds.

Keywords: 2026

How to Cite:

Blackburn, H., Browning, R., Hay, E., Hayes, E. & Ling, A., (2026) “Estimated proportions of Bos taurus and Bos indicus admixture in Mashona and Tuli, ancient composites from Zimbabwe”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2295805. doi: https://doi.org/10.31274/wcgalp.24372

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