Teratospermia in Domestic Cats Compromises Penetration of Zona‐Free Hamster Ova and Cat Zonae Pellucidae

The ability of spermatozoa to bind and penetrate zona‐free hamster ova and the zonae pellucidae of domestic cat oocytes in vitro was compared between normospermic (>60% structurally normal spermatozoa per ejaculate) and teratospermic (<40% normal spermatozoa per ejaculate) domestic cats. The effects of culture media (Biggers, Whitten, Whittingham [BWW] versus modified Krebs Ringer bicarbonate [mKRB]) and simple dilution (DR), ejaculate centrifugation, and either resuspension (NS) or swim‐up processing (SU) on penetration also were examined. High percentages of structurally normal spermatozoa were bound to zona‐pellucida‐free hamster ova regardless of the morphological forms in the inseminant. Mean percent normal spermatozoa bound to ova in DR, NS, and SU sperm aliquots from teratospermic male cats were not different (P > 0.05) from similarly treated normospermic aliquots. However, the percent penetration of hamster ova by normospermic ejaculates (10.5%) was superior (P < 0.05) to that of teratospermic ejaculates (2.8%). Although swim‐up processing improved percent sperm motility, progressive motility, and normal morphology in teratospermic ejaculates (P < 0.05), no difference was observed in ovum penetration among the DR‐treated, NS‐treated, and SU‐treated spermatozoa (P > 0.05). Culture medium had no effect on sperm binding in the hamster assay, but ovum penetration rate by spermatozoa in the normospermic ejaculates was enhanced (P < 0.05) using mKRB (13.5%) when compared with BWW (7.6%) medium. Spermatozoa from teratospermic cats were capable of binding and penetrating cat zonae; however, sperm—zona interaction (defined as percent of oocytes with spermatozoa binding to or penetrating into the zona) was different (P < 0.05) between normospermic (65.3%) and teratospermic (24.2%) cats. The number of bound spermatozoa per ovum was five‐fold less in males producing high proportions of pleiomorphic spermatozoa (P < 0.05). Zona penetration was also different between normospermic (58.1%) and teratospermic (16.9%) males. Within cat populations, the DR, NS, and SU treatments had no influence on sperm binding or zona penetration. These results indicate that teratospermia in domestic cats has a detrimental impact on gamete interaction and penetration of zona‐free hamster ova and cat zonae pellucidae. The in vitro effect is not entirely dependent on absolute numbers of structurally normal spermatozoa but appears to be related to an unidentified characteristic of teratospermic ejaculates. 1991 American Society of Andrology