The researchers split bull sperm into different groups based on how they move using a computer program. They found that in the first round of sperm from Japanese black bulls, there were more sperm that moved quickly in circles with wide heads. In the second round, there were more sperm that moved at a medium speed with heads moving frequently in a short distance. The first round had a greater proportion of the fast and wide-headed moving sperm and a lower proportion of moderately moving sperm compared to the second round. Ultimately, the study showed that there are different types of moving sperm in bulls, and the proportions can change between the first and second rounds of ejaculates.