Estrous Synchronization in the Persian Onager (Equus hemionus onager)
American Association of Zoo Veterinarians Conference 2015
Julia M. Ter Beest1, MS, DVM; Mandi W. Schook2, PhD
1The Wilds, Cumberland, OH, USA; 2Cleveland Metroparks Zoo, Cleveland, OH, USA


The Persian onager (Equus hemionus onager) has experienced significant population declines over the past century due to poaching, habitat destruction and fragmentation, and resource competition.1 Artificial insemination (AI) may be particularly useful in this species as a means of introducing genetic material from captive-bred individuals to small, isolated wild populations that lack movement corridors to achieve such an exchange. The first successful AI in captive-bred Persian onagers was performed in 2013, at the Wilds in southeast Ohio, USA, and it utilized urine hormone analyses and regular ultrasound examinations.2 A method for estrous synchronization in this species would alleviate the need for daily handling and injections and may provide a more feasible approach to AI. This study tested long-acting, controlled-release preparations of estradiol and progesterone, followed by a single injection of prostaglandin in six adult female Persian onagers to determine whether ovulation would occur within a narrow window. Means and standard deviations were determined for the lengths of follicular and luteal phases, follicle sizes, and time to ovulation. All six onagers ovulated between days 18 and 22, with three onagers ovulating on day 19, as determined by the presence of a corpus luteum visualized during transrectal ultrasound. This is an apparently safe and effective method for the synchronization of estrus in the Persian onager and may be used to develop a timed AI protocol for use at institutions that do not have specialized handling facilities to enable regular transrectal ultrasound for following follicular development.


Cleveland Zoological Society generously provided funding for this project, with in-kind support from the Wilds and Cleveland Metroparks Zoo.

Literature Cited

1.  Feh C, Shah H, Rowen M, Reading R, Goyal SP. Status and action plan for the Asiatic wild ass (Equus hemionus). In: Moehlman PD, ed. Equids: Zebras, Asses, and Horses. Status Survey and Conservation Action Plan. Gland, Switzerland: IUCN; 2002:62–71.

2.  Schook MW, Wildt DE, Weiss RB, Wolfe BA, Archibald KE, Pukazhenthi BS. Fundamental studies of the reproductive biology of the endangered Persian onager (Equus hemionus onager) result in first wild equid offspring from artificial insemination. Biol Reprod. 2013;89(2):1–13.


Speaker Information
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Julia M. Ter Beest, MS, DVM
The Wilds
Cumberland, OH, USA

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