Genome-wide association study for calving performance using high-density genotypes in dairy and beef cattle

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Livestock Production

Background:

• Calving difficulty and perinatal mortality are significant issues in cattle production.
• Genetic factors contribute to these traits, but their genomic architecture is poorly understood, especially in beef breeds.

Purpose of the Study:

• To elucidate the genomic architecture of calving difficulty and perinatal mortality.
• To identify specific genomic regions associated with these traits in beef cattle breeds.

Main Methods:

• Genome-wide association study (GWAS) using high-density genotypes.
• Employed single-nucleotide polymorphism (SNP) regression and Bayesian approaches.
• Utilized imputed sequence data for refined association analysis and candidate gene identification.

Main Results:

• Detected significant genomic regions associated with direct and maternal calving difficulty and perinatal mortality.
• Identified breed-specific associations on various chromosomes, with notable findings on chromosomes 18 and 2 for direct calving difficulty.
• Refined associations using sequence data, identifying candidate genes like CTU1 and PCLO with potential impacts on calving traits.

Conclusions:

• The genomic architecture of calving performance is complex, involving numerous small-effect polymorphisms.
• Identified moderate effect size associations, predominantly breed-specific, indicating the presence of unique alleles or varying linkage phases.
• Suggests that a portion of genetic variation for calving performance is shared across breeds.