USING URINARY HORMONE ANALYSIS TO PREDICT GENDER AND ASSESS FETAL VIABILITY IN THE INDIAN RHINOCEROS (Rhinoceros unicornis)

The high incidence of stillbirth (16% of all births) within the global captive propagation program for Indian rhinoceros (Rhinoceros unicornis) has been a major impediment to achieving a sustainable population.2 Many factors have been linked to stillbirth incidence in domestic livestock including: parity, sex of offspring and gestation length. Recent analysis of studbook data indicates primiparous Indian rhinoceros dams experience less perinatal death and stillbirths compared to pluriparous dams.2,3 While sex ratio at birth remains fairly equal in this species (54% male), the majority of stillbirths (67%) have been associated with male calves.2 As fetal gender may be a contributing factor in stillbirth in the Indian rhinoceros, knowledge of the sex of calves in utero could help identify those dams at a potentially higher risk. Knowing the gender of an expected calf would provide institutions and the rhinoceros taxon advisory group (TAG) more lead time to plan for housing requirements and subsequent breeding recommendations if viable births occur. Developing a non-invasive means to determine sex of an Indian rhinoceros fetus could potentially benefit this species and the zoo community. In this study, we examined if urinary hormone analysis of maternal testosterone (T), cortisol (C) and corticosterone (C1) could be used to establish physiologic markers to predict gender, parturition date and potentially assess fetal viability during pregnancy in the Indian rhinocersos. While urinary C has been validated for Indian rhinoceros,1 it has not yet been examined during gestation, and the pattern of excretion as it relates to timing of parturition and birth outcome is unknown. To validate urinary C1, samples collected during a previously conducted adrenocorticotropic hormone (ACTH) stimulation test were utilized.1 Longitudinal urine samples were collected starting on day of breeding (3 dams) or AI (3 dams), continued throughout gestation and for 1 wk post parturition. Of the six pregnancies monitored, three resulted in live births of female calves at 477.67 ± 6.96 days (range 465-489 days) postbreeding (n = 2) or AI (n = 1); two resulted in live births of male calves at 481 ± 1 days postbreeding (n = 1) or AI (n = 1); and one resulted in birth of a male calf at 490 d post-AI that exhibited signs of respiratory distress and died ~12 hr post-parturition. Although sample size was low, we found no difference (P = 0.452) in gestation length between dams carrying female versus male calves.