Peripheral plasma oestradiol-17β, progesterone and cortisol in buffaloes induced to calve with dexamethasone and vetoestrol

Abstract

Ten pregnant Murrah buffaloes were used to compare effects of combined dexamethasone (DEX) and stilboestrol-dipropionate (Vetoestrol, V) on parturition and on hormone changes in peripheral blood plasma; while five animals served as controls receiving no treatment, the other five animals received, intramuscularly, 30 mg DEX and 30 mg V at the same time. Three treated buffaloes required a second injection of DEX and V 4 days after first administration to precipitate calving. Buffaloes in the control group calved 309 ± 35 days after breeding as compared to 284 ± 1.2 days for the treated animals. Placental retention occurred in all treated buffaloes and in none of the untreated buffaloes. Mean service period, services/conception and milk yield/day of the treated animals were similar ( P > 0.05) to their previous records. The mean plasma oestradiol-17β concentration in the control animals showed a gradual rise from 30 to 5 days prepartum ( P < 0.05), followed by a steep increase to peak level 1 day prepartum. Animals treated with a single injection showed a similar trend. Those which required two injections showed a fluctuating hormone rise to peak levels after the first injection, the levels subsequently declining to lower concentrations by the time of the second injection. After the second injection the hormone concentration increased steeply prior to calving. The mean plasma progesterone concentration in the control animals declined gradually from 30 to 2 days ( P < 0.05) prepartum, then fell sharply to low levels at calving ( P < 0.01). While the animals treated with a single injection showed a similar trend, the other animals showed no distinct pattern between injections, but the hormone level declined sharply after the second injection to record low levels at calving. The mean plasma cortisol concentration remained more or less constant during the pre- and postpartum periods, only rising sharply to a peak at calving in the control group. However, in all the induced animals, the DEX treatment brought about a sharp decline in cortisol concentration in blood. The data suggest that for normal expulsion of fetal membranes a rise in oestradiol-17β prepartum must be accompanied by a fall in progesterone, and that this shift should occur in a gradual and sustained manner.