Species-specific sperm-egg interaction affects the utility of a heterologous bovine in vitro fertilization system for evaluating antelope sperm

The purpose of this study was to evaluate cryopreserved fringe-eared (FE) o ryx (Oryx gazella callotis) sperm function using a heterologous in vitro fe rtilization (IVF) system previously developed to study scimitar-horned (SH) oryx (Oryx dammah) spermatozoa. Semen was collected by electroejaculation from FE oryx (n = 2) and SH oryx (n = 2), evaluated immediately postcollect ion, and cryopreserved. Thawed spermatozoa were evaluated for motility, for ward progression, and acrosomal status immediately post-thaw, after Percoll -separation, and 1, 2, 3, and 8 h after culture in IVF medium. In vitro-mat ured cow oocytes (n = 924) were inseminated with either domestic bull, FE, or SH oryx spermatozoa and after an 8-h coincubation period, half the oocyt es were fixed and examined for sperm penetration, polyspermy, and male pron uclear formation. The remaining oocytes were placed into in vitro culture a nd evaluated for cleavage after 48 h. Overall, there were no between-specie s differences in sperm motility and acrosome integrity. However, an effect of time (P < 0.05) and a species-by-time interaction (P < 0.05) were detect ed for both parameters. Penetration, male pronuclear formation, and embryo cleavage were high (> 90%, > 85%, and > 70%, respectively) for oocytes inse minated with domestic bull and SH oryx spermatozoa and did not differ (P > 0.05) between species. In contrast, very few oocytes (2.8%, 4 of 141) insem inated with FE oryx sperm were penetrated. Cleavage was rare (8.0%, 16 of 2 00) in oocytes inseminated with FE oryx spermatozoa and did not differ (P > 0.05) from that in parthenogenetic controls (4.2%, 3 of 72). Furthermore, FE oryx spermatozoa were incapable of penetrating zona-free cow oocytes. Th ese results indicate that species-specific differences in gamete interactio n may exist even between very closely related nondomestic bovids.