Characterization of rabbit sperm by equilibrium sedimentation in Percoll during frequent ejaculation

Qualitative and quantitative changes of rabbit sperm were observed during frequent ejaculation. Semen volume, sperm concentration, percentage of motility, and fertility index of Farris (FI) decreased with frequent ejaculation, and these values recovered to initial levels after a 24-day abstinence period. A remarkable change was found in the sperm distribution profile in Percoll density gradients after equilibrium sedimentation. The main peak of sperm was shifted from fraction number 4 on the first day of ejaculation to number 7 on the fifth day. Fraction numbers 1-4 showed a high percentage of motility, whereas the sperm motility from fraction numbers 7-10 was quite low. Motile and morphologically mature sperm had higher apparent density than immotile or immature sperm. This suggests that rabbit sperm motility might be related to the apparent density of the sperm cell.