Serum cortisol and progestin concentrations in pregnant and non-pregnant Asian elephants ( Elephas maximus)

Abstract

Blood samples were collected during the estrous cycle ( n = 3), throughout gestation ( n = 3), and during the periparturient period ( n = 11) to assess serum concentrations of cortisol in pregnant and non-pregnant Asian elephants whose reproductive status was being monitored by serum progestin determination. While serum cortisol concentrations remained constant throughout gestation, progestin concentrations decreased significantly ( p < 0.05) in the second half of pregnancy, declining to undetectable levels by 3 days before calving. During the non-luteal phase of the estrous cycle serum progestins varied from undetectable levels to 100 pg/ml (53 ± 10.7 pg/ml) then increased steadily during the luteal phase (322 ± 207.5 pg/ml). There were no significant differences between serum cortisol concentrations during the luteal and those of the non-luteal phase ( p > 0.05). The mean cortisol concentration during the estrous cycle was about twice that during pregnancy ( p > 0.05). No substantial changes in maternal cortisol were found during the course of pregnancy or the periparturient period.