Variance components for bovine tuberculosis infection and multi-breed genome-wide association analysis using imputed...

Area of Science:

• Animal Genetics
• Veterinary Science
• Genomics

Background:

• Bovine tuberculosis (bTB), caused by Mycobacterium bovis, remains a significant challenge in cattle eradication programs.
• The national bTB eradication program in the Republic of Ireland has not yet achieved its goal of biological extinction.
• Understanding genetic resistance is crucial for developing effective control strategies.

Purpose of the Study:

• To develop statistical methods for routine genetic evaluations of bTB resistance in cattle.
• To identify bovine genomic regions associated with bTB infection in dairy and beef breeds.
• To utilize imputed whole genome sequence data and beef breeds for novel association analyses.

Main Methods:

• Employed linear mixed models to quantify variance components for bTB.
• Conducted within-breed and multi-breed genome-wide association studies using a single-SNP regression approach.
• Utilized phenotypic bTB data from 781,270 animals and imputed whole genome sequence data from 7,346 sires.

Main Results:

• Estimated heritability (0.12) and repeatability (0.30) for bTB resistance indicate potential for genetic selection.
• Multi-breed genome-wide association analysis identified 38 SNPs and 64 quantitative trait loci (QTL) regions linked to bTB infection.
• Two significant QTL regions on BTA23 were consistently identified across multi-breed and specific within-breed analyses.

Conclusions:

• Genetic selection offers a viable strategy to aid in the eradication of bovine tuberculosis.
• The study identified key genomic regions associated with bTB resistance, providing targets for future research.
• The developed methodology will inform national genetic evaluations for bTB in the Republic of Ireland and contribute to understanding cattle disease resistance mechanisms.