Lack of ovulation is common in captive southern white rhino females and contributes to poor reproductive success. We show that ovulation can be induced efficiently with exogenous hormones using a single treatment protocol. This information can lead to improved genetic management of captive populations acting as insurance against extinction.
The ex situ Indian rhino population experienced a decrease in genetic diversity indicating that the breeding program could possibly benefit from novel reproductive management strategies to ensure population sustainability. We sought to determine how management tools used for reproductive management, specifically translocation and operant conditioning, impact physiological and behavioral measures of welfare in Indian rhinos. First, an adrenocorticotropic hormone challenge performed in an adult male resulted in a 38-fold increase in urinary and a 3.5-fold increase in fecal glucocorticoid metabolites (FGM). Mean and peak FGM differed among three females, but all demonstrated elevated (P < 0.0001) concentrations for variable durations after translocation that lasted up to 9 weeks. Lastly, behavioral and adrenal responses of two females to operant conditioning to stand during transrectal ultrasound exams were monitored and rhinos differed in their mean and peak FGM concentrations. However, FGM were not different before versus during training or on pasture versus in the barn. One female exhibited more stereotypic behavior during training in the barn than on pasture (P < 0.05); although, stereotypies (1.73% of time) were relatively uncommon overall. In summary, individual variation exists in FGM both at baseline levels and in response to a stressor. In addition, while a transient rise in glucocorticoid activity post-translocation indicated that Indian rhinos have a physiological response to changes in their environment, minor alterations in daily routines using operant conditioning only resulted in minimal changes in behaviors and FGM.
All extant species in the Rhinocerotidae family are experiencing escalating threats in the wild, making self‐sustaining captive populations essential genetic reservoirs for species survival. Assisted reproductive technologies (ARTs) will become increasingly important for achieving and maintaining ex situ population sustainability and genetic diversity. Previous reports have shown that a large proportion of captive southern white rhinoceros (SWR) females are irregularly cyclic or acyclic, and that cycling females display two different estrous cycle lengths of approximately 30 or 70 days. It has been suggested that the longer estrous cycle length is infertile or subfertile, as no term pregnancies have been observed following long cycles. Here we report the achievement of two pregnancies following long luteal phases, using ovulation induction and artificial insemination with either fresh or frozen‐thawed semen. One female SWR conceived on the first insemination attempt and gave birth to a live offspring. A second female conceived twice in consecutive long cycles although the first embryo was resorbed by 33 days post‐insemination. A pregnancy from this female's second insemination is ongoing with expected parturition in November 2019. Whether prolonged estrous cycles in SWR are subfertile or infertile in natural breeding situations remains unclear. However, our findings demonstrate that the application of ARTs following prolonged cycles can result the successful establishment of pregnancies in SWR. Therefore, with ARTs, female SWR otherwise considered nonreproductive due to long estrous cycles may still have the potential for representation and contribution to the ex situ population.
The extant Rhinocerotidae family is experiencing threats in the wild, making captive populations important genetic reservoirs for species survival. Because each species faces distinct challenges in captivity, populations are not self-sustaining. Therefore, assisted reproductive technologies (ART) such as AI will be necessary to maintain or increase captive genetic variation. Captive-born female white rhinoceros (Ceratotherium simum simum) have low reproductive rates and apparent acyclicity is a common issue. Although females fail to ovulate and progesterone remains at baseline levels, follicle growth may occur and ovulation can be induced with exogenous hormones. Female southern white rhinos (n=6) housed as a bachelorette group were determined to be ovulatory (n=1) or anovulatory (n=5) by serial ultrasound and fecal progesterone (P4; ng g−1) analysis. However, all anovulatory females grew follicles beyond preovulatory size, which then regressed. At the time of study, when follicles were preovulatory size (35.4±1.2 mm; mean±SD), anovulatory females (n=4) were induced to ovulate (n=11) with a gonadotropin releasing hormone (GnRH) agonist (4.5mg, SucroMate™; Bioniche Animal Health, Bogart, GA, USA) in a single intramuscular injection. Nine treatments resulted in ovulation (81.8%), all between 36 and 48h post-treatment, while 2 hemorrhagic anovulatory follicles (18.2%; HAF) formed, both in the same female. Ovulations were confirmed by disappearance of the follicle by 48h and P4 elevation above baseline was coincident with corpus luteum (CL) and HAF formation. All resulting luteal structures were included in analysis. Follicle growth was permitted to proceed without GnRH treatment between inductions (n=6); dominant follicles grew beyond preovulatory size (43.8±6.1mm) followed by regression and growth of another preovulatory follicle that was subjected to GnRH treatment. Data were analyzed by R studio (ver. 1.1.383). Luteal phases were characterized as “short” (<50 days) or “long” (>50 days). Only P4 above baseline (days) was significantly different (P<0.05) between long and short cycles. Other cycle parameters, such as CL visibility (days), time from ovulation to P4 above baseline (days), maximum P4 (ng g−1), and maximum luteal size (mm), were not significantly different between cycle types. Both cycle types were observed following both spontaneous (short, n=5; long, n=3) and induced ovulations (short, n=8; long, n=3). These data provide additional insight into the differences between long and short cycles and that GnRH is a reliable and effective method to overcome anovulation in SWR. We also prove that long cycle lengths are not necessarily indicative of early pregnancy loss, as has been previously suggested. Taken together, this information can enhance captive breeding efforts and the genetic diversity of the ex situ, SWR insurance population.
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