An Investigation of Ovarian and Adrenal Hormone Activity in Post-Ovulatory Cheetahs (Acinonyx jubatus)

Abstract

Cheetahs have been the subject of reproductive study for over 35 years, yet steroid hormone activity remains poorly described after ovulation. Our objective was to examine and compare fecal progestagen (fPM), estrogen (fEM), and glucocorticoid (fGM) metabolite concentrations post-ovulation in pregnant and non-pregnant animals to better understand female physiology (1) during successful pregnancy, (2) surrounding frequent non-pregnant luteal phases, and (3) after artificial insemination (AI) to improve the low success rate. Secondarily, the authors also validated a urinary progestagen metabolite assay, allowing pregnancy detection with minimal sample collection. Fecal samples were collected from 12 females for ≥2 weeks prior to breeding/hormone injection (the PRE period) through 92 days post-breeding/injection. Samples were assessed for hormone concentrations using established enzyme immunoassays. Urine samples were collected for 13 weeks from 6 females after natural breeding or AI. There were no differences among groups in fGM, but in pregnant females, concentrations were higher (p < 0.01) in the last trimester than any other time. For pregnant females that gave birth to singletons, fGM was higher (p = 0.0205), but fEM tended to be lower (p = 0.0626) than those with multi-cub litters. Our results provide insight into the physiological events surrounding natural and artificially stimulated luteal activity in the cheetah.

Keywords: artificial insemination; cheetah; estrogen; glucocorticoid; hormone; pregnancy; progestagen.

Figure 1

Time period raw means (a) and three representatives (b) fecal progestagen metabolite (fPM) profiles for female cheetahs experiencing ovulatory events: pregnant, confirmed by birth of cubs, or a non-pregnant luteal phase (NPLP) following natural breeding or exogenous hormone stimulation and artificial insemination (AI), but no cubs resulted. In (a), different lower-case letters denote differences (p < 0.05) among time periods for all ovulatory events. Asterisk indicates a difference from other trimesters in the pregnant condition only. In (b), alternatively shaded sections indicate PRE time period and three trimester divisions.

Figure 2

Time period predicted mean concentrations for fecal estrogen metabolites (fEM) from female cheetahs experiencing ovulatory events: pregnant, confirmed by birth of cubs, or a non-pregnant luteal phase (NPLP) following natural breeding or exogenous hormone stimulation and artificial insemination (AI), but no cubs resulted. Different lower-case letters denote differences (p < 0.05) among time periods for all ovulatory events.

Figure 3

Predicted (a) and raw (b) fecal glucocorticoid metabolite (fGM) time period means for female cheetahs experiencing ovulatory events: pregnant, confirmed by birth of cubs, or a non-pregnant luteal phase (NPLP) following natural breeding or exogenous hormone stimulation and artificial insemination (AI), but no cubs resulted. In (a), all ovulatory events were combined to determine overall model-predicted means. Different lower-case letters denote differences (p < 0.05) among time periods. Asterisk indicates a difference (p < 0.05) from all other time periods in the pregnant condition only.

Figure 4

Raw (a) fecal glucocorticoid metabolite (fGM) and (b) fecal estrogen metabolite (fEM) means for pregnant female cheetahs that gave birth to a litter of more than one offspring (n = 10) compared to hormone concentrations collected during pregnancies in which females gave birth to a singleton cub (n = 5). Asterisk denotes significance (p < 0.05), and plus sign denotes a tendency (p = 0.063).

Figure 5

Weekly raw mean urinary progestagen metabolite concentrations in samples collected from female cheetahs after natural breeding or hormone administration and either giving birth to offspring (pregnant), or exhibiting fecal progestagen metabolite concentrations indicative of ovulation, but no offspring were produced (NPLP). Elevated values were determined to be all those above a value three times a non-ovulatory mean baseline urinary progestagen metabolite concentration (1.5 ng/mg CRT). The shaded area indicates the three-week term in which pregnant values were higher than NPLP concentrations (p < 0.001).