Natural and gonadotropin-induced ovarian activity in tigers (Panthera tigris) assessed by fecal steroid analyses

Fecal samples were collected from female tigers (n = 17) to compare endocrine patterns associated with natural ovarian activity with those after chorionic gonadotropin ovulation induction and artificial insemination (AI). Baseline fecal estradiol concentrations were 65.77 ± 3.61 ng/g with estrual peaks of 167.39 ± 9.92 ng/g and an anovulatory cycle length of 17.96 ± 0.70 days. Peak fecal estradiol was higher when females were housed with a male for breeding (262.30 ± 41.43 vs. 165.30 ± 3.67 ng/g; P < 0.05). The majority of animals showed some seasonal differences in fecal estradiol however, patterns were inconsistent. Fecal progestagens increased only after breeding confirming tigers are primarily induced ovulators. The non-pregnant luteal phase was 34.50 ± 1.85 days in duration. In pregnant tigers, fecal progestagens remained elevated for 108 days until parturition and the diagnosis of pregnancy was possible based on the elevated fecal progestagens after 35 days of gestation. Tigers were administered equine chorionic gonadotropin (eCG) to stimulate follicular growth and human chorionic gonadotropin (hCG) to induce ovulation prior to AI [200 IU eCG/100 IU hCG (n = 5); 400 IU eCG/200 IU hCG (n = 2); 500 IU eCG/100 IU hCG (n = 2); 1000 IU eCG/750 IU hCG (n = 11); 1000 IU eCG/1000 IU hCG (n = 4)]. None of the tigers subjected to AI became pregnant (n = 9). Fecal endocrine patterns in gonadotropin-stimulated tigers were considerably different from those observed in naturally bred tigers. In particular, fecal estradiol concentrations were higher than those observed during natural estrus and remained elevated for longer periods of time in tigers administered the higher doses of gonadotropins typically used in conjunction with AI in this species. These abnormal endocrine patterns may help explain the poor success rate of AI in this species.