Characterization of estrous cyclicity in the sable antelope (Hippotragus niger) through fecal progestagen monitoring.

Fecal progesterone metabolite monitoring techniques were validated for the sable antelope and used to characterize ovarian cycle dynamics and reproductive seasonality in a captive population at the National Zoological Park's Conservation and Research Center. Hormone was homogeneously distributed within fecal samples. Longitudinal fluctuations in fecal progesterone metabolites were consistent with typical luteal phase patterns and corresponded closely with changes in serum progesterone. The lag time from an im injection of progesterone to peak excretion in feces was 16 h. The pattern of births showed a slight peak in the summer (May-July), but year-round endocrine monitoring of six nonpregnant females showed no evidence of seasonality in ovarian activity. Females exhibited 11-14 estrous cycles per year, averaging 24.2 +/- 0.9 days in length. Luteal and interluteal phases were 18.4 +/- 0.9 and 5.8 +/- 0.4 days in length, respectively. Although only a small number of hippotragine antelope species have been studied, data indicate that they exhibit considerable interspecific variability in estrous cycle length and reproductive seasonality and thus may be a useful group for further investigation of factors regulating fertility.