An Investigation of Ovarian and Adrenal Hormone Activity in Post-Ovulatory Cheetahs (Acinonyx jubatus)

SIMPLE SUMMARY: More than three decades of scientific study have been unable to determine the etiology of reproductive issues in cheetahs under human care. The reproduction of cheetahs in zoological facilities has never been self-sustaining, and the differences between females who establish pregnancy and those that do not remain poorly understood. The objective of this study was to examine and compare ovarian and adrenal hormones post-ovulation in pregnant and non-pregnant animals to better understand female physiology after natural breeding or artificial insemination, and determine what may be contributing to the frequent lack of success. The authors also sought to validate a urinary progestagen assay to assist with pregnancy detection. Although fecal glucocorticoid metabolites among pregnant and non-pregnant groups were not different, samples from the third trimester in pregnant animals were higher than at any other time. Additionally, glucocorticoids were higher, and estrogens tended to be lower in samples from pregnant females that gave birth to singletons, than those that had multi-cub litters. As a supplementary benefit, this is the first time urinary progestagens have been measured and have been able to distinguish pregnant and non-pregnant cheetahs. The results provide first-time insights into ovarian and adrenal hormonal events surrounding ovulation and pregnancy detection in cheetahs. ABSTRACT: Cheetahs have been the subject of reproductive study for over 35 years, yet steroid hormone activity remains poorly described after ovulation. Our objective was to examine and compare fecal progestagen (fPM), estrogen (fEM), and glucocorticoid (fGM) metabolite concentrations post-ovulation in pregnant and non-pregnant animals to better understand female physiology (1) during successful pregnancy, (2) surrounding frequent non-pregnant luteal phases, and (3) after artificial insemination (AI) to improve the low success rate. Secondarily, the authors also validated a urinary progestagen metabolite assay, allowing pregnancy detection with minimal sample collection. Fecal samples were collected from 12 females for ≥2 weeks prior to breeding/hormone injection (the PRE period) through 92 days post-breeding/injection. Samples were assessed for hormone concentrations using established enzyme immunoassays. Urine samples were collected for 13 weeks from 6 females after natural breeding or AI. There were no differences among groups in fGM, but in pregnant females, concentrations were higher (p < 0.01) in the last trimester than any other time. For pregnant females that gave birth to singletons, fGM was higher (p = 0.0205), but fEM tended to be lower (p = 0.0626) than those with multi-cub litters. Our results provide insight into the physiological events surrounding natural and artificially stimulated luteal activity in the cheetah.