Towards the understanding of bull fertility: phenotypic traits description and candidate gene approach

We presented the preliminary results of the analysis of semen phenotypic and quality data provided by ANARB along with the result of SNPs discovery on seven candidate genes for male fertility and the ongoing study on mtDNA. The phenotypic data recorded by Computer Assisted Sperm Analyzer of fresh semen for 1,014 bulls were evaluated. The least squared means of volumes were lower than data in literature generally referred to mature bulls, whereas the spermatozoa concentrations, total and progressive motility were satisfactory. As expected in young bulls, the percentage of spermatozoa morphological abnormalities was high. The SNPs discovery in seven candidate genes revealed 30 new SNPs and confirmed the polymorphism in STAT5A gene. The complete sequencing of mtDNA of 48 extreme bulls for semen phenotypic traits revealed 274 mutations. Association between SNPs and semen phenotypes is on going. Our results represent a preliminary step towards the sounding of genetic mechanisms of bull fertility and highlight the paramount importance of reliable phenotypes for association studies.