Induction of abortion during midgestation in mares.

Four standardbred mares, 99 to 153 days pregnant, were treated with a synthetic prostaglandin analogue, prostalene, in an attempt to induce abortion. The mares received subcutaneous injection of either 2 mg prostalene (recommended luteolytic dose); 4 mg prostalene (double luteolytic dose) or 4 mg twice at intervals of 12 hours or 24 hours. The prostalene treatment resulted in cervical relaxation, increased tone of the uterus and decreased plasma concentrations of progesterone. None of the pregnant mares aborted within seven days after the first prostalene treatment. Abortions were subsequently induced by single or multiple intrauterine infusions using warm hypertonic saline. There were no postabortion complications.