The effect of long non-reproductive periods on the genital health in captive female white rhinoceroses (Ceratotherium simum simum, C.s. cottoni)

Activation of southern white rhinoceros (Ceratotherium simum simum) estrogen receptors by phytoestrogens: potential role in the reproductive failure of captive-born females?

The captive southern white rhinoceros (SWR; Ceratotherium simum simum) population serves as an important genetic reservoir critical to the conservation of this vulnerable species. Unfortunately, captive populations are declining due to the poor reproductive success of captive-born females. Captive female SWR exhibit reproductive problems suggested to result from continual ovarian follicular activity and prolonged exposure to endogenous estrogen. However, we investigated the potential role of exogenous dietary phytoestrogens in the reproductive failure of SWR by cloning and characterizing in vitro phytoestrogen binding and activation of recombinant SWR estrogen receptors (ESR). We compared those characteristics with recombinant greater one-horned rhinoceros (GOHR; Rhinoceros unicornis) ESR, a species that receives similar captive diets yet reproduces relatively well. Our results indicate that phytoestrogens bind rhino ESR in a manner similar to other vertebrate species, but there are no differences found in phytoestrogen binding affinity of SWR ESR compared with GOHR ESR. However, species-specific differences in ESR activation by phytoestrogens were detected. The phytoestrogen coumestrol stimulated greater maximal activation of SWR ESR1 than GOHR ESR1. SWR ESR2 were also more sensitive to phytoestrogens and were activated to a greater extent by both coumestrol and daidzein. The concentrations in which significant differences in ESR activation occurred (10(-7) to 10(-5) m) are consistent with circulating concentrations measured in other vertebrate species. Taken together, these findings suggest that phytoestrogens potentially pose a risk to the reproductive health of captive SWR. However, additional studies are needed to further clarify the physiological role of dietary phytoestrogens in the reduced fertility of this species.

Fecal corticosterone concentrations and reproductive success in captive female southern white rhinoceros

Prolonged or frequent secretion of adrenal glucocorticoids in response to aversive stimuli can negatively impact reproduction. Because female southern white rhinoceros (Ceratotherium simum simum) reproduce poorly in captivity, we compared fecal corticosterone metabolite concentrations among parous, nulliparous, and adolescent females and examined social and physical aspects of the captive environment that might be related to differences in corticosterone metabolite concentrations. Aggression, dominance, sexual and play interactions, social group size and composition, enclosure size, and other housing characteristics were assessed though behavioral observations and review of historical and institution records. Concentrations of metabolized corticosterone in fecal samples were analyzed by enzyme immunoassay. The proportion of nulliparous females did not differ (p>0.05) between subordinate and dominant animals, and subordinates did not have a higher mean fecal corticosterone concentration than dominants (p>0.05). Of the behaviors examined, only the frequency of sexual play behaviors differed (p<0.05) between dominants and subordinates. Average corticosterone concentrations differed (p<0.05) across housing institutions but were not consistently elevated (p>0.05) for females housed in most of the environmental conditions assessed. Housing with a female companion known from adolescence, however, tended to be associated (p=0.06) with a lower mean corticosterone concentration than that when housing with a female companion introduced during adulthood or no female companion. Wild-caught females had a higher (p<0.05) average corticosterone concentration than captive-born females. Average corticosterone concentration did not differ (p>0.05) between acyclic and cycling, or nulliparous and parous females.

Dystocia and fetotomy associated with cerebral aplasia in a greater one-horned rhinoceros (Rhinoceros unicornis)

The captive greater one-horned rhinoceros population consists of 176 animals. Since 1971, a total of 226 calves were born into this captive population. However, 24% of the offspring born were either stillborn or did not survive the first 3 months. The causes for this high rate of stillbirth and neonate mortality have not yet been documented. Here, we report on the veterinary management of a dystocia and foetotomy resulting from a malpositioned greater one-horned rhinoceros foetus. The dead foetus presented with a forelimb flexed at the shoulder joint, with all other joints extended. The foetus was dissected into five parts and extracted during two anaesthesias on two consecutive days. The dam recovered fully and came into oestrous 31 days after surgery. Post-mortem and CT examination of the malformed foetal head revealed cranioschisis with cerebral aplasia and cerebellar hypoplasia. The cerebral aplasia presented here and in other recent cases suggests that neural tube defects and cranial malformations may be associated with more captive rhinoceros stillbirths than previously considered. Epidemiologic studies of these phenomena and possible nutritional deficiencies or hereditary defects are warranted.

A case of metastatic uterine adenocarcinoma in a southern white rhinoceros (Ceratotherium simum simum)

A 39-yr-old, acyclic, uniparous, female white rhinoceros with a history of recurrent vaginal bleeding was euthanized following a period of respiratory distress and ill-thrift. The rhinoceros' uterus had previously been evaluated by ultrasound and diffuse endometrial hyperplasia and two benign uterine leiomyomas had been diagnosed. At necropsy examination, a large, infiltrative, metastatic uterine adenocarcinoma was found multifocally throughout the uterus, scattered within the peritoneal cavity, on the diaphragm, the splenic capsule, the pleural surface of the lung and mesenteric lymph nodes. A large volume (100 L) of ascites fluid was present in the abdominal and pleural cavities.

Seminoma in a southern black rhinoceros (Diceros bicornis minor): diagnosis, surgical management and effect on fertility

A testicular mass was identified by ultrasonography performed during a routine reproductive evaluation of an adult male southern black rhinoceros (Diceros bicornis minor). Histological examination of a testicular biopsy supported a presumptive diagnosis of testicular neoplasia. Hemi-castration was performed to excise the affected testis and a pathological diagnosis of a seminoma was made. Assessment of semen suggested reduced fertility as a consequence of the neoplastic process, but hemi-castration prevented further growth and metastasis of the tumour and ensured the animal's breeding potential. This is the second documented case of a seminoma in a rhinoceros species and the first case in a black rhinoceros.

Ovarian superstimulation, transrectal ultrasound-guided oocyte recovery, and IVF in rhinoceros

Numerous reports on reproductive pathology in all rhinoceros species illustrate the abundance of female infertility in captive populations. In infertile rhinoceroses, oocyte collection and embryo production could represent the best remaining option for these animals to reproduce and to contribute to the genetic pool. We report here on superstimulation, repeated oocyte recovery, and attempted in vitro fertilization (IVF) in white and black rhinoceroses. Four anestrous rhinoceroses (two white, two black) with unknown follicular status were treated with gonadotropin-releasing hormone analogue, deslorelin acetate, for 6 to 7 d. Number and size of follicles in superstimulated females was significantly higher and larger compared with those in nonstimulated anestrous females (n=9). Ovum pick-up was achieved by transrectal ultrasound-guided follicle aspiration. Up to 15 follicles were aspirated per ovary. During six ovum pick-ups, a total of 29 cumulus-oocyte complexes (COCs) were harvested with a range of 2 to 9 COCs per collection. No postsurgical complications were noted on the rhinoceros ovaries using this minimally invasive approach. Various in vitro maturation (IVM) and IVF protocols were tested on the collected COCs. Despite the low total number of COCs available for IVM and IVF in this study, we can report the first rhinoceros embryo ever produced in vitro. The production of a 4-cell embryo demonstrated the potential of transrectal ultrasound-guided oocyte recovery as a valuable tool for in vitro production of rhinoceros embryos from otherwise infertile females.

Frozen-thawed rhinoceros sperm exhibit DNA damage shortly after thawing when assessed by the sperm chromatin dispersion assay

This study reports on the successful validation (via in situ nick translation and neutral comet assay) of the equine Sperm-Halomax kit as an appropriate methodology for the assessment of sperm DNA fragmentation in three species of rhinoceros. Rhinoceros sperm nuclei with fragmented DNA (validated using in situ nick translation) were evident as large halos with dispersed DNA fragments, whereas those with nonfragmented DNA displayed small halos of nondispersed DNA within the microgel. There was a high correlation (r) of 0.974 (R(2) value=0.949; P<0.01; n=16) between the respective assessments of the Sperm Chromatin Dispersion test (SCDt) and the neutral comet assay. Application of the SCDt to determine the DNA fragmentation dynamics of rhinoceros (n=6) sperm frozen in liquid nitrogen vapor and incubated postthaw at 37 degrees C for up to 48 h to mimic in vitro conditions in the female reproductive tract, revealed an increase (P=0.001) in DNA damage, as soon as 4h after the start of incubation. Linear regression equations were calculated for all six rhinoceroses over the first 6h of incubation and revealed individual animal variation. Freshly collected and incubated (37 degrees C) rhinoceros (n=3) sperm had no increase in the basal level of DNA fragmentation for up to 48 h, indicating that the cryopreservation of rhinoceros sperm in liquid nitrogen vapor, as used in this study, appeared to result in freeze-thaw DNA damage.

Split-sample comparison of directional and liquid nitrogen vapour freezing method on post-thaw semen quality in white rhinoceroses (Ceratotherium simum simum and Ceratotherium simum cottoni)

To increase the quality of cryopreserved sperm in white rhinoceros, the liquid nitrogen vapour (LN vapour) freezing and the multi-thermal gradient directional freezing methods were compared. Sixteen white rhinoceros (Ceratotherium simum sp.) were electro-ejaculated. Semen samples were diluted with cryoextender (Tris, lactose, egg-yolk, DMSO) and aliquoted into straws for LN vapour freezing, and glass hollow tubes for directional freezing. The sperm quality was evaluated before and after freezing by assessing the following parameters: motility, morphologic state, acrosomal integrity and plasma membrane function and integrity (i.e. sperm viability) as defined by the hypo-osmotic swelling. Directional freezing improved the sperm viability by 5.6% (p<0.005), progressive motility score by 34.7% and sperm motility index (SMI) by 8.1% (p<0.005) versus LN vapour freezing. When data was categorized into groups of low (<19%), moderate (20-39%) and high (>40%) percentages of morphologically normal, directional freezing (DF) resulted in 31.4% less abnormal acrosomes for the low quality group as well as 18.7% increase in intact acrosomes and 10.9% increase in motility for the high quality group compared to LN vapour freezing (LN) (p<0.01, p<0.03, p<0.01, respectively). LN showed a significant reduction in sperm head volume (5.7%, p<0.05) compared to the prefreeze; whereas, no significant reduction in head volume was demonstrated after DF. Several additives (xanthenuric acid, cytochalasin D, potassium, EDTA) to the basic cryoextender provided no significant improvement in spermatozoal survival after directional freezing. In conclusion, directional freezing proved to facilitate higher gamete survival compared to LN vapour freezing. This is especially effective in ejaculates of low sperm quality and is important in endangered species where high quality semen donors are often not accessible. These results suggest that directional freezing could be valuable particularly for species with limited freezability of spermatozoa.

Aging and fertility patterns in wild chimpanzees provide insights into the evolution of menopause

Human menopause is remarkable in that reproductive senescence is markedly accelerated relative to somatic aging, leaving an extended postreproductive period for a large proportion of women. Functional explanations for this are debated, in part because comparative data from closely related species are inadequate. Existing studies of chimpanzees are based on very small samples and have not provided clear conclusions about the reproductive function of aging females. These studies have not examined whether reproductive senescence in chimpanzees exceeds the pace of general aging, as in humans, or occurs in parallel with declines in overall health, as in many other animals. In order to remedy these problems, we examined fertility and mortality patterns in six free-living chimpanzee populations. Chimpanzee and human birth rates show similar patterns of decline beginning in the fourth decade, suggesting that the physiology of reproductive senescence was relatively conserved in human evolution. However, in contrast to humans, chimpanzee fertility declines are consistent with declines in survivorship, and healthy females maintain high birth rates late into life. Thus, in contrast to recent claims, we find no evidence that menopause is a typical characteristic of chimpanzee life histories.

Assisted Reproduction in Female Rhinoceros and Elephants ? Current Status and Future Perspective

Over the last few decades, rhinoceroses and elephants became important icons in the saga of wildlife conservation. Recent surveys estimate the wild Asian (Elephas maximus) and African (Loxodonta africana) elephant populations to be, at most, 50 250 and 637 600 respectively. For the five rhinoceros species, black (Diceros bicornis), white (Ceratotherium simum), Indian (Rhinoceros unicornis), Javan (Rhinoceros sondaicus) and Sumatran rhinoceros (Dicerorhinus Sumatrensis), the population estimates of 3610, 11 330, 2400, 60 and 300, respectively, are of even greater concern. Protected against habitat loss, poaching and left undisturbed, rhinoceros and elephants reproduce well in the wild. But small and decreasing populations make successful captive management of these taxa increasingly important. In captivity, however, most populations face possible 'extinction' because of historically poor reproductive performance. From the first descriptions of the reproductive anatomy and the oestrous cycle (Laws 1969; Kassam and Lasley 1981; Balke et al. 1988a,b; Plotka et al. 1988; Godfrey et al. 1991) to the present use of advanced assisted reproduction technologies, researchers have strive to understand the function and dysfunction of the reproductive biology of these charismatic species. This paper reviewed the current knowledge on rhinoceros and elephant reproduction biology, reproductive cycle, gestation, dystocia, reproductive pathology, oestrous induction and artificial insemination, sperm sexing, IVF and contraception, and how this knowledge is or might be used to aid species conservation for maximal reproductive efficiency and enhancement of genetic management.

Artificial insemination in the anoestrous and the postpartum white rhinoceros using GnRH analogue to induce ovulation

The objective of this study was to develop AI and to achieve first time pregnancy in a nulliparous rhinoceros. For this, one 24-year-old irregular cycling female white rhinoceros was selected, which had never been mated. The endocrine function was monitored by faecal and serum pregnane analysis. Ultrasound determined the optimal day for AI by measuring follicle sizes of 2.0, 2.6, 3.0, 3.2 cm on days -6, -4, -1, 0 of the induced oestrous cycle, respectively. AI was performed and ovulation induced when a pre-ovulatory-sized follicle was present using GnRH analogue, deslorelin. Fresh semen was deposited in the uterine horn using a patented AI catheter overcoming the hymeneal membrane and torturous cervical folds non-surgically. Moreover, ultrasound monitoring of the uterine involution and ovarian activity on days 16, 26, 30 postpartum facilitated the induction of and the AI on the first postpartum oestrous in a rhinoceros using GnRH analogue. Two consecutive pregnancies were achieved by AI for the first time in the rhinoceros. Pregnancies were diagnosed by elevated serum and faecal 20-oxo-pregnane concentrations. In addition ultrasound measured biometric parameters of the two foetuses on days 86 and 133 of gestation. Two female calves were born after 490 and 502 days of gestation, yet one calf was stillborn. AI in rhinoceros might now be used as assisted reproduction technology tool to boost critically small captive rhinoceros populations.