Effects of Estrous Bovine Cervical Mucus on Capacitation and the Acrosome Reaction of Frozen-Thawed Spermatozoa in Vitro.

Cervical mucus was collected from Holstein cows in estrus. Frozen-thawed spermatozoa were separated from seminal plasma by swim-up method for 1h (ME spermatozoa) or penetration through fresh mucus for 50-70 min (MU spermatozoa). The separated spermatozoa were incubated for 5 and 11 h and assessed for sperm motility, viability and proportion of the acrosome reaction. Motility and viability were significantly increased in the separated spermatozoa than in those before separation. However, MU spermatozoa lost their motility and viability more rapidly than ME spermatozoa during incubation by for 11h. Proportion of the acrosome reaction was always higher in MU than in ME spermatozoa during the incubation. Exposure of ME and MU spermatozoa to lysophosphatidylcholine did not alter the proportion of the acrosome reaction during the incubation. These results indicate that cervical mucus selects only motile spermatozoa and induces sperm capacitation and the acrosome reaction during migration in it.