Induction of lambing: comparison of the effects of prostaglandin, oestradiol benzoate and dexamethasone

Abstract

In the first of two experiments 45 ewes were treated on day 141 of gestation with either prostaglandin F 2 a or saline. Doses of 10, 15, 20 or 25 mg PGF 2a failed to induce lambing earlier than in control animals. A further 50 ewes were similarly treated on day 144; neither dose level of PGF aa nor day of administration had any effect on the interval from injection to lambing compared with controls. In a second experiment 159 ewes were randomly assigned to one of four treatment groups as follows: (1) 20 mg oestradiol benzoate (ODB); (2) 16 mg dexamethasone; (3) 15 mg PGF 2a ; (4) 2 ml saline. Ewes were injected on either day 143 or 144 of gestation and on each of those days animals were injected either in the morning or evening. The mean times to induction of lambing were 38-6 + 20-8; 44-2+18-1; 83-5±39-8 and 82-9±43-lh for the four treatments respectively. Neither day nor time of treatment had any significant effect on the interval to lambing. Both ODB and dexamethasone induced parturition earlier than PGF 2a or saline (P < 005).

Comparison of the behaviour of Romney and Merino ewes lambing on slopes

“…The observation periods lasted 38-48 h for each group oflambing ewes and 35%of Merino and 51% of Romney ewes were observed to lamb. This would support published data where the interval from dexamethasone injection to lambing is longer in Merino ewes (mean 62-63 h: Owens et al 1985) than in other breeds (mean 43-47 h: Bose 1972;Webster & Haresign 1981;Boland et al 1982). …”

Expression of steroidogenic enzymes in placentome of ewes with pregnancy toxemia after two parturition induction methods

“…Since PGFS, PTGES and their receptors were upregulated in caruncle, direct contribution to endometrial prostaglandin production by aglepristone may be argued. From another point of view, an existing placental steroid production could be masked by metabolism or aglepristone could only contribute to immune and inflammatory processes leading to parturition, by stimuli of fetal signal to the endometrial Due to mimicking fetal cortisol, dexamethasone applications are recommended to induce parturition and gluconeogenesis in traditional treatment protocols for decades in pregnancy toxemia (Boland et al, 1982;Harman and Slyter, 1980). Nevertheless, dystocia and/or insufficient cervical dilatation are significantly higher diagnosed in pregnancy toxemia, with or without dexamethasone.…”