The use of prostaglandin F2alpha in controlling the oestrous cycle of the mare and steroid changes in the peripheral blood. 
Prostaglandin F2alpha (PGF2alpha), administered by untrauterine infusion and intramuscular injection, was used to induce oestrus and ovulation in non-cyclic mares.  A satisfactory response rate (80% or more) was obtained and the dose (2-5--7-5 mg) and the time taken for ovulation to occur (up to 9 days) was the same irrespective of the route of administration.  Only about one-half of the mares conceived to mating at the induced oestrus but the low conception rate could be attributed to the infertile condition of the mares.  Plasma progesterone remained at basal levels after PGF2alpha and oestrogen levels were inconsistent.  The use of PGF2alpha in the treatment of severe endometritis was successful in one mare.