Measuring fecal progestogens as a tool to monitor reproductive activity in captive female bottlenose dolphins (Tursiops truncatus)

Abstract 

The objective was to develop and test radioimmunoassays (RIAs) to measure fecal progestogens (P) and estrogens (E) to monitor ovarian activity in the bottlenose dolphin (Tursiops truncatus). Fecal samples were collected at least once a week for 20 mo from three peripubertal female bottlenose dolphins. Blood samples were collected at least once a month to compare serum and fecal steroid concentrations. Moreover, random fecal samples from three pregnant females, one lactating female, and one sexually mature female receiving oral altrenogest treatment were also collected. Fecal samples were collected behaviorally with a probe to avoid water contamination and extracted with petroleum ether (for P analysis) or diethyl ether (for E analysis). When possible, vaginal cytology and ovarian ultrasonography were used to monitor the estrous cycle. The RIA for fecal P had good reproducibility and negligible matrix effect. In addition, when fecal samples (N=25) were extracted with ethanol, the results with the two methods of extraction were highly correlated (r=0.923). Therefore, extraction of fecal samples with petroleum ether represented a valid alternative to other, more time-consuming methods of determining fecal P concentrations. In the absence of luteal activity, fecal P concentrations were consistently < 10pmol/g feces, although they never decreased below 10pmol/g during pregnancy. Thus, the threshold to confirm the presence of an active corpus luteum was provisionally set at 10pmol/g. Around the onset of puberty, luteal phases appeared shorter and irregular in the bottlenose dolphin, as in other mammalian species. Additional HPLC-MS studies should be performed to identify predominant P metabolites to be used as fecal indicators of luteal activity in this species.

Keywords: Dolphins, Estrous cycle, Fecal progestogens, Pregnancy, Radioimmunoassay