Review: Genetic mutations affecting bull fertility.

Area of Science:

• Animal Genetics
• Reproductive Biology
• Quantitative Genetics

Background:

• Cattle serve as a valuable model organism for studying male reproductive performance due to extensive genomic and phenotypic data.
• Artificial insemination and genomic prediction in cattle provide large datasets for genetic analysis of fertility traits.

Purpose of the Study:

• To identify genetic factors contributing to variation in male reproductive performance in cattle.
• To investigate the genetic basis of both monogenic reproductive disorders and quantitative fertility traits.

Main Methods:

• Genome-wide association testing (GWAS) using microarray-derived genotypes and detailed semen quality/insemination success phenotypes.
• Case-control association testing for identifying alleles responsible for monogenic reproductive disorders.
• Variance components estimation utilizing repeated semen quality measurements.

Main Results:

• Several causal recessive loss-of-function alleles for monogenic reproductive disorders were identified and are now monitored in breeding bulls.
• Genome-wide association studies identified quantitative trait loci (QTL) associated with male fertility, though underlying causal variants remain largely unknown.
• The identified QTL explain only a small proportion of the total heritability for male fertility.

Conclusions:

• Genetic analysis in cattle has successfully identified specific alleles causing reproductive disorders and highlighted QTL for fertility.
• Further integration of omics data (gene expression, etc.) with GWAS is crucial for fine-mapping causal variants underlying quantitative male fertility traits.
• Monitoring genetic variants aids in improving artificial insemination efficiency and overall herd reproductive performance.