Release of prostaglandin F, regression of corpora lutea and induction of premature parturition in goats treated with estradiol-17beta.

Premature parturition was induced in five pregnant goats infused intravenously with 4.65-8.4 mg estradiol-17beta but not in one treated with 5.85 mg estradiol-17alpha. A single intramuscular injection of 12 mg estradiol benzoate (8.8 mg estradiol-17beta equivalents) was also effective. These doses were estimated to provide plasma concentrations of estradiol-17beta in the physiological range for animals at sponteneous parturition. Circulating plasma concentrations of progesterone decreased and lactogenesis occurred before all instances of induced parturition but no such changes resulted from infusion of estradiol-17alpha. Placental delivery was normal in all animals but neonates of more than 10 days prematurity were non-viable.