MONITORING OVARIAN-FUNCTION IN SCIMITAR-HORNED ORYX (ORYX DAMMAH) BY MEASUREMENT OF FECAL 20-ALPHA-PROGESTAGEN METABOLITES

The feasibility of monitoring ovarian function in scimitar-horned oryx (Oryx dammah) by measurement of fecal 20 alpha-progestagens was inves tigated. Fecal samples were collected daily or on alternate days over a 4-11 month period from five oryx during natural (n = 4) or synthetic PGF(2 alpha) (cloprostenol)-controlled (n = 1) cycles. Of the four or yx undergoing natural cycles, three had regular access to a vasectomis ed male, and mating dates were recorded. Ultrasonography was used to m onitor changes in reproductive tract morphology in the female administ ered with cloprostenol. Neutral steroids were extracted from feces wit h methanol:petroleum ether (2:1 v/v) after first removing phenolic ste roids with potassium hydroxide (1 M). The concentration of 20 alpha-pr ogestagens in the methanol phase was measured by enzymeimmunoassay. Ex cretion of 20 alpha-progestagens in all females followed a cyclic patt ern corresponding to the follicular and luteal phases of the ovarian c ycle. Concentrations of fecal 20 alpha-progestagens were on average tw entyfold greater during the luteal phase compared with the follicular phase. Mean (+/-SD) ovarian cycle length, based on fecal progestagen p rofiles, was 24.4 +/- 2.2 days with mean (+/-SD) luteal and follicular phase lengths of 18.7 +/- 2.8 and 5.7 +/- 1.6 days, respectively. Mat ing by a vasectomized male occurred when 20 alpha-progestagen concentr ations were still elevated or declining. Similarly, fecal progestagens did not return to follicular phase concentrations for 4-5 days after administration of cloprostenol, and a 4 day delay was observed between ovulation, as visualized by ultrasound scanning, and a rise in fecal 20 alpha-progestagens. These data suggest a time lag of approximately 4 days between reproductive events and changes in fecal 20 alpha-proge stagen concentrations. We conclude that measurement of immunoreactive 20 alpha-progestagen concentrations in feces has limited application f or predicting ovulation or accurately timing inseminations because of delay in steroid excretion, but will enable noninvasive monitoring of ovarian cycles in scimitar-horned oryx for fertility assessment and fo r determining the outcome of artificial insemination programs. (C) 199 5 Wiley-Liss, Inc.