OVARIAN ACTIVITY IN THE SCIMITAR-HORNED ORYX (ORYX DAMMAH) DETERMINEDBY FECAL STEROID ANALYSIS

Ultrasonography and radioimmunoassay (RIA) of serum oestradiol-17 beta , luteinizing hormone (LH) and progesterone, and faecal oestrogen and progestin was used to assess ovarian activity in the scimitar-horned o ryx (Oryx dammah). Ovarian examination using ultrasonography revealed maximal follicle and corpus luteum (CL) diameters of 15 and 32 mm, res pectively. Steroid hormone metabolite distribution among individual fa ecal pellets within the same defaecation was relatively homogeneous wi th coefficients of variation averaging 10.2 +/- 1.8% and 16.2 +/- 4.6% for oestrogens and progestins, respectively. Elevated faecal oestroge n concentrations were associated with large (> 10 mm) antral follicles detected by ultrasonography. Periovulatory peaks in faecal oestrogen excretion, coincident with nadirs in progestin excretion, were detecte d in three females. Faecal progestin excretion exhibited a similar tem poral pattern to serum progesterone concentrations, with a time lag of approximately 16 h. Faecal progestin concentrations corresponded with the presence of functional CL and proved useful for monitoring luteal function, spontaneous and prostaglandin-F-2 alpha analogue-induced lu teolysis and anovulation. In summary, faecal steroid monitoring is a p ractical, noninvasive method for characterising ovarian steroid excret ion and has potential for facilitating the application of assisted rep roductive technologies in scimitar-horned oryx. (C) 1998 Elsevier Scie nce B.V. All rights reserved.