Ovarian Ultrasonography Correlated with Fecal Progestins and Estradiol During the Estrous Cycle and Early Pregnancy in Giraffes (Giraffa camelopardalis rothschildi)1

Abstract

Fecal and urinary progestin analyses have shown that giraffes express a short reproductive cycle, averaging 15 days, compared with other large ruminants. However, actual ovarian events have not been correlated with the hormonal pattern. In this study, mature cycling female Rothschild giraffes (Giraffa camelopardalis rothschildi) were repeatedly examined by transrectal ultrasonography to correlate ovarian function with changes in fecal progestin (fP4 [n(c) = 6]) and estradiol (fE2 [n(c) = 6]) and serum progestin (n(c) = 2) as measured by enzyme immunoassay. Five females became pregnant and were monitored during early gestation. In this study, we discovered that hormone values for fP4 in cycling giraffes do not correlate with the classic profile of follicular development, ovulation, and luteogenesis. The corpus luteum (CL) and the next dominant follicle were forming simultaneously. A mean +/- SD peak in fE2 of 254.92 +/- 194.76 ng/g and subsequent ovulation occurred as early as 1 day after the fall in fP4. In pregnant giraffes, the CL reached a diameter significantly larger (mean +/- SD, 41.02 +/- 2.70 mm; P = 0.0126) than that during the cycle (33.48 +/- 2.80 mm), while follicular activity and fluctuating fE2 were still present. With this research, we demonstrated that the progesterone profile typically used to characterize the ovarian cycle does not correlate with luteal development in the ovaries of this species. Furthermore, we conclude that the giraffe could have evolved a short reproductive cycle because of the almost parallel order of ovarian events.

Luteogenesis during the estrous cycle in Asian elephants (Elephas maximus)

“…As soon as P m reached baseline (follicular phase) values, follicles started developing. This is in contrast to other megavertebrae species such as giraffe (Lueders et al 2009) or rhinoceros (Radcliffe et al 1997) where follicles are constantly forming in all reproductive stages, even under the influence of a functional CL. In elephants, high P m levels appear to completely inhibit antral follicle formation.…”

“…In other species, rapid ultrasonographically visible CL formation can be seen within 1-3 days, with full development by w10 days post ovulation (giraffe: Lueders et al 2009;sheep: Jablonka-Shariff et al 1993;mare: Harrison 1946). In the elephant, it took w40 days …”

“…The luteal cells of the acCLs may require the second LH peak to mature and become fully steroidogenically active. In Baringo giraffes (Giraffa camelopardalis rothschildi) and white rhinoceros (Ceratotherium simum simum) a time span of 5-6 and 7-9 days respectively has been reported from ovulation to first rise in progesterone levels (Radcliffe et al 1997, Lueders et al 2009). The short period from ovulation to increased P m concentrations in the Asian elephant supports the hypothesis that the acCL may initially be responsible for secreting this hormone while the ovCL contributes and maintains P m during the remainder of the luteal phase.…”

“…The P m concentrations of animals in group 1 were determined from the serum through EIA using a previously published protocol (Graham et al 2001) with slight modifications (Szdzuy et al 2006, Lueders et al 2009). In brief, the progesterone CL425 antibody and the conjugate supplied by Coralie Munro (University of California, Davis, CA, USA) were diluted 1:6000 and 1:10 000 respectively.…”

Ovarian and placental morphology and endocrine functions in the pregnant giraffe (Giraffa camelopardalis)

“…Only a single, large (3-5 cm diameter) pregnancy CL is present in one of the maternal ovaries and it persists throughout gestation (Amoroso & Finn 1962, Kayanja & Blankenship 1973, Hall-Martin & Rowlands 1980, Lueders et al 2009a, 2009b. Progestins have been isolated from the ovaries of fetal, juvenile, pregnant and non-pregnant giraffe (Gombe & Kayanja 1974), and it was originally postulated that a placental gonadotrophin might be responsible for the follicular activity and luteinisation seen in the fetus (Kellas et al 1958) following a report of gonadotrophic hormones in the urine of a pregnant giraffe by Wilkinson & De Fremmery (1940).…”