Comparative aspects of estrus synchronization, ovulation induction, and embryo cryopreservation in the scimitar‐horned oryx, bongo, eland, and greater kudu

Comparative studies were conducted to evaluate the efficacy of estrus synchronization, ovulation induction, nonsurgical embryo collection, and cryopreservatin procedures in the scimitar‐horned oryx (Oryx dammah), bongo (Tragelaphus euryceros), eland (Taurotragus oryx), and greater kudu (Tragelaphus strepsiceros). In the scimitar‐horned oryx, a 6α‐methyl‐17α‐acetoxyprogesterone (MAP) pessary vs. prostaglandin F₂α (PGF₂α) estrus synchronization treatment was compared; only PGF₂α was tested in the other species. Ovarian responsiveness to follicestimulating hormone (FSH‐P, b.i.d. for 5 days) or pregnant mare's serum gonadotropin (PMSG, single injection) was evaluated in all species. MAP and PGF₂α were equally effective (P < 0.05) for synchronizing estrus in scimitar‐horned oryx. Signs of estrus, including mounting, were observed in 15 of 33 (45.4%) oryx donors, but copulation was observed on only 8 occasions. Mean number of CL/ovulating bongo and eland female was enhanced (P < 0.05) by FSH‐P compared to PMSG (4.5 ± 1.8 vs. 1.3 ± 0.3 CL/bongo and 10.6 ± 4.6 vs. 1.0 ± 0.6 CL/eland, respectively) treatment. The difference in mean (± SEM) CL number between FSH‐P‐ and PMSG‐treated oryx donors approached significance (4.6 ± 1.6 vs. 2.7 ± 0.8, respectively; P = 0.08). Embryos and ova were recovered nonsurgically from 10 of 19 (52.6%) of the ovulating oryx, 9 of 10 (90%) bongo, 6 of 10 (60%) eland, and both (100%) greater kudu. A high proportion (60%) of cryopreserved oryx embryos maintained an excellent‐or good‐quality grade (QG) after thawing. A higher proportion (P < 0.05) of embryos frozen in 1.5 M dimethyl sulfoxide (6 of 10) or 1.5 M glycerol (6 of 10) solutions maintained their prefreeze QG compared to the propylene glycol counterparts (3 of 10). The transfer of thawed embryos to synchronized oryx recipients (n = 9) resulted in no pregnancies. Conventional techniques for synchronizing ovarian activity, inducing ovulation, and flushing the uterine content of farm livestock largely are adaptive to these African antelope species. However, the overall efficiency of these strategies for consistently promoting superovulation and large numbers of embryos is relatively low. For these species, the primary limitations to effective embryo recovery and transfer appear to be: 1) a lack of estrous behavior which contributes to a low incidence of mating and, thus, poor fertilization and recipient synchrony, and 2) a resilience of the ovaries to conventional gonadotropic preparations.