The use of synthetic prostaglandin analogue (fluprostenol) to induce foaling.

The synthetic prostaglandin (PG) analogue fluprostenol was used to induce parturition in mares and its mode of action was investigated by measuring endocrine changes before and during the induction period. Progestagens and unconjugated oestrogens showed little change during the induction period, but two different patterns in plasma PGFM levels were observed. The first was seen when foaling occurred within 90 min of injection; PGFM levels rose soon after injection and peaked during the maximum expulsive stage of labour, thus resembling events during natural foaling. The second occurred when foaling took longer than 90 min, and in these mares PGFM levels rose at various times after injection and peaked well before the onset of the expulsive stage of labour. It is suggested that these differences reflect the hormonal readiness of the mares to foal. Other procedures, such as rupture of the allantochorion, and dilatation of the cervix and injection of fluprostenol into the allantois, produced no uterine activity and did not stimulate labour or PGFM release.