Trypanosomosis: potential driver of selection in African cattle

Area of Science:

• Animal Genetics
• Disease Resistance
• Livestock Breeding

Background:

• Trypanosomosis significantly reduces cattle productivity in tsetse-fly zones.
• Taurine cattle (e.g., Baoule) exhibit trypanotolerance, while Zebu cattle are susceptible but larger.
• Crossbreeding aims to enhance production and disease resistance in cattle.

Purpose of the Study:

• To compare zebuine and taurine admixture in cattle genomes, focusing on regions linked to trypanotolerance.
• To identify differences in allele frequencies between tolerant and non-tolerant animals.
• To guide future breeding strategies for trypanotolerant, high-production cattle.

Main Methods:

• Genomic analysis of 214 cattle (Baoule, Zebu, composites) using 25 microsatellites and 155 SNPs.
• Analysis of admixture levels in background genome and 23 candidate regions.
• Calculation of fixation index (F ST) to assess breed differentiation.

Main Results:

• Baoule admixture was higher in candidate regions (0.37) than the overall genome (0.31).
• Strong genetic differentiation between breeds was observed (F ST ≥ 0.20 in nine regions).
• Six regions showed significant admixture differences from background, with five favoring Baoule ancestry.

Conclusions:

• Genomic regions associated with trypanotolerance show distinct admixture patterns.
• Excess Baoule ancestry in specific regions suggests a genetic basis for tolerance.
• Understanding breed composition is vital for developing more productive, disease-resistant cattle.