What can bulls tell us about men? Researchers lack data on the quality of semen and on molecular markers from sufficiently large cohorts of healthy men of reproductive age. The path to a better understanding of which genes and mechanisms control male fertility therefore lies via suitable laboratory animals – in this case, bulls. Many genes involvedThrough this research, the team discovered a large number of genes and their variants that are associated with fertility in bulls. Currently, every bull’s ejaculate is tested for quality before use and the calves’ genomes are analysed; however, some infertile bulls still slip through.