The use of prostaglandin F2alpha-tham salt in mares in clinical anoestrus.

Seventy-three Standardbred and Thoroughbred mares in clinical anoestrus during the breeding season were treated with PGF2alpha. The mares were divided into four categories; foaling, barren, maiden and unknown. The response was consistent in all groups. Mares at Days 2 to 4 of dioestrus showed no decrease in plasma progesterone levels, and those at Days 6 to 8 showed a return of progesterone to baseline levels (less than 1 ng/ml) in 24 to 48 hr after treatment. Plasma progesterone levels returned to basal levels in 24 to 48 hr in 93% of mares; progesterone levels had not changed by 96 hr in 7% of the treated mares. Behavioural oestrus was detected in 71% of treated mares an average of 4-4 days after treatment, and ovulation occurred in 86% at an average of 8-9 days. Pregnancy occurred in 55-5% of the PGF2alpha-treated mares after an average of 1-7 services during the induced oestrus.