Genome-wide association study of beef bull semen attributes

Area of Science:

• Animal Genetics
• Reproductive Biology
• Quantitative Genetics

Background:

• Cattle fertility is crucial for production, with semen attributes assessed in breeding soundness exams.
• Semen quality indicators include volume, concentration, motility, and morphology.
• Genetic factors significantly influence male fertility traits in beef bulls.

Purpose of the Study:

• To conduct a single-step genome-wide association study (ssGWAS) for beef bull semen attributes.
• Identify genomic regions associated with key fertility indicators.
• Provide a basis for improving male fertility through genetic selection.

Main Methods:

• Utilized a dataset of 1819 Angus bulls with 50,624 semen collection records.
• Employed a five-generation pedigree and genotype data from the American Angus Association.
• Performed ssGWAS using a multi-trait animal model to estimate single nucleotide polymorphism (SNP) effects.

Main Results:

• Identified significant SNPs associated with semen volume, concentration, sperm count, and motility (initial and post-thaw).
• Detected SNPs linked to percentage of normal spermatozoa and primary/secondary abnormalities.
• Multiple genome-wide significant SNPs were found for all measured semen attributes.

Conclusions:

• Significant SNPs were located near or within quantitative trait loci (QTL) for semen attributes.
• Genes associated with fertility were found in proximity to significant SNPs.
• Integrating genomic information into genetic evaluations can enhance the genetic improvement of male fertility traits.