Use of urinary hormone assays for evaluating endocrine patterns associated with the long-day breeding season in Eld's deer (Cervus eldi).

Reproductive seasonality and pregnancy in the endangered brow-antlered or Eld's deer (Cervus eldi) were studied by measuring urinary estrone conjugates (EC) and pregnanediol-3 alpha-glucuronide (PdG) profiles in voided urine. Based on the excretion of PdG, female Eld's deer were seasonally polyestrous, spontaneous ovulators with regular cyclic activity beginning in January to March and ending in August to October. The overall estrous cycle averaged 21.5 +/- 2.1 days (+/- SEM, n = 65); however, 2 of 13 does consistently produced prolonged cycles (30.1 +/- 4.4 days, n = 14). Behavioral estrus (approximately 12-24 h duration) was observed in 42 of 65 cycles and always occurred when PdG excretion was at nadir levels. In two does that were serially bled, preovulatory plasma LH peaks occurred coincident with estrus, and progesterone secretion paralleled PdG excretion. Mean gestation duration (n = 10) was 33.5 +/- 0.4 wk with PdG concentrations increasing markedly during pregnancy (especially the last 25 wk) before an abrupt decline coincided with parturition. Mean EC excretion remained low during much of gestation; however, significant increases in this metabolite were observed, particularly during the 4 wk immediately preceding parturition. The results are the first to demonstrate the utility of atraumatic urinary hormone monitoring for studying the endocrinology of cervids. Excreted urinary PdG accurately reflects circannual fluctuations in cyclic ovarian activity, and longitudinal increases in this metabolite are highly indicative of pregnancy. Cyclic ovarian activity cannot be clearly monitored by urinary EC concentrations, although this metabolite can be used in conjunction with elevated PdG levels to confirm pregnancy and perhaps estimate the onset of impending parturition.