Reproduction professor at the University of Calgary John Kastelic says, nutrition management on young bulls is crucial to their success on the ranch. But many factors contribute to bull fertility. That's why it's important to thoroughly examine bulls for structural problems, abnormalities, and semen quality, among others. "In terms of bull fertility, the bull must be able to identify cows that are in estrus, he must be able to mount and breed those cows and deliver large numbers of normal sperm. If there is a deficit in any one of those or more than one of those, bull fertility will be very limited. Therefore when we are examining bulls, we look at the health and the well-being of the bull, his structural soundness. Does he have normal feet and legs, are his eyes and mouth normal, is he free from evidence of infectious disease or any structural deficits, for example, problems with his feet and or legs or any other abnormalities that would impair his health and well-being, we then measure the scrotal circumference, it's important to do that correctly so we get an accurate measurement, we collect and evaluate semen. The usual minimum standards are maximum 30% abnormal sperm cells maximum 20% sperm with head defects, minimum 30% motility. We have minimum standards for scrotal circumference which may vary from one breed to another.