Abstract
To develop new tests to predict bull subfertility, a mucus penetration test, in which penetration of cervical mucus by spermatozoa is quantitated, was applied using frozen-thawed semen and a test to examine the ability of spermatozoa to undergo the acrosome reaction in response to calcium and the calcium ionophore A23187 (A23187 stimulation test) was attempted. Frozen-thawed spermatozoa from 4 Japanese black bulls (2 fertile and the other 2 subfertile) were analyzed by standard semen analysis such as sperm concentration, motility, viability and morphology, the mucus penetration test and the A23187 stimulation test, and the relationship of the test results to fertility status was investigated retrospectively. The results of the standard semen analysis and the mucus penetration test did not reveal any remarkable differences among the bulls, showing no relationship to fertility status. However, when spermatozoa were stimulated with 3 mM Ca2+ and 1 μM A23187, the bulls all showed a time-dependent induction of the acrosome reaction but the subfertile bulls showed a slower and lower induction than the fertile bulls. These results suggest that A23187 stimulation test may be useful when abnormal sperm characteristics cannot be found by standard semen analysis or the mucus penetration test.
