Comparing ovulation synchronization protocols for artificial insemination in the scimitar-horned oryx (Oryx dammah)

Ovarian response and pregnancy success in scimitar-horned oryx (n=28) were compared, following treatment with two synchronization protocols and fixed-time artificial insemination (AI) with frozen-thawed semen. Each oryx received two injections of 500 μg of prostaglandin-F2α analogue (PGF2α-only) 11 days apart, and half received PGF2α in combination with an intravaginal progesterone-releasing device (CIDR11+PGF2α). Semen was collected by electroejaculation from anaesthetised adult oryx and cryopreserved. Anaesthetised females were transcervically inseminated 56.0±1.1 h (±S.E.M.) after PGF2α injection and/or device withdrawal using 28.0±1.5×106 motile thawed sperm. Ovarian endocrine response was monitored in 20 females by analysing faecal oestrogen and progesterone metabolites. Periovulatory oestrogen peaks were detected in 19/20 (95%) females after synchronization. There were no between-treatment differences in oestrogen concentrations or peak characteristics (P>0.05). Luteal development after synchronization was delayed in half the progesterone treated (CIDR11+PGF2α) females, and faecal progestin excretion profiles indicated that the ovulatory follicle associated with synchronization either failed to ovulate or to fully lutenise. Pregnancy was diagnosed by ultrasonography and/or rectal palpation and was monitored by faecal progestin excretion. More (P=0.013) pregnancies resulted from the PGF2α-only treatment (37.5%, 5/14) than from the CIDR11+PGF2α treatment (0/14), and four healthy scimitar-horned oryx calves were born, three after gestation intervals of 247 days and one after 249 days.