ZONA-PELLUCIDA BINDING AND ZONA-INDUCED ACROSOME REACTIONS IN HORSE SPERMATOZOA - COMPARISONS BETWEEN FERTILE AND SUBFERTILE STALLIONS

Diagnostic tests that probe sperm function are needed to determine the potential etiologies of subfertility and to explore treatments of sub fertility in stallions. Using epifluorescence and phase contrast micro scopy, a comparison was made between ejaculates from 3 fertile and 3 s ubfertile stallions in which sperm-zona pellucida binding and acrosoma l status were measured. Motile spermatozoa were selected by Percoll gr adient centrifugation and were capacitated in vitro using TEST:TALP ca pacitation medium at 39 degrees C under humidified air containing 5% C O2. Concentration of motile spermatozoa was held constant during coinc ubation with oocytes for fertile and subfertile ejaculates. The total number of zona pellucida-bound spermatozoa was higher for fertile stal lions than for subfertile stallions (P < 0.05). Similarly, the percent age of acrosome reactions in zona pellucida-bound spermatozoa was high er for the 3 fertile stallions than for the 3 subfertile stallions (P < 0.05). These results indicate that spermatozoa from fertile stallion s may interact with female gametes differently from that of subfertile stallions and suggest that sperm functions are measurable and may var y with fertility.