Functional capacity and fertilizing longevity of frozen-thawed scimitar-horned oryx (Oryx dammah) spermatozoa in a heterologous in vitro fertilization system

This study was conducted to determine if cryopreservation and thawing reduc es the quality of scimitar-horned oryx spermatozoa and thus might be respon sible for sub-optimal artificial insemination (Al) efficiency. Functional c apacity of frozen-thawed oryx spermatozoa was compared in a heterologous bo vine in vitro fertilization (IVF) system after being prepared by four metho ds. Fertilizing longevity was also assessed after thawing and pre-incubatin g spermatozoa for 12 or 24 h before IVF. Sperm characteristics (viability, morphology, acrosomal and capacitation status) were superior for samples pr epared by Percoll centrifugation and standard swim-up compared with microdr op swim-up and wash methods. Regardless of variation in sperm characteristi cs over time, fertilization success and embryo development were high and di d not differ among treatments. Fertilization and cleavage success for sperm atozoa pre-incubated for 12 h before IVF were comparable with that achieved with non-incubated spermatozoa. Even 24 h after thawing, spermatozoa were capable of fertilizing oocytes, but percentage fertilization and embryo cle avage were significantly lower than for spermatozoa pre-incubated for 12 h. Overall, functional capacity of oryx spermatozoa after thawing appears com parable with that of domestic bull spermatozoa. When used for Al, frozen-th awed oryx spermatozoa should be capable of fertilizing oocytes in females o vulating 12 or even 24 h after insemination, providing sperm transport mech anisms are adequate. The functional capacity and fertilizing longevity of o ryx sperm after thawing is high, and therefore unlikely to be responsible f or decreased Al efficiency in the scimitar-horned oryx.