Induced abortion with two prostaglandin F2 alpha analogues in mares: plasma progesterone changes.

This research involves testing the effects of two prostaglandin F2 alpha analogues on aborting pregnancies in mares during mid-gestation, labelling the related change in plasma progesterone levels.

Objective

This research aimed to evaluate the abortive potential of two types of Prostaglandin F2 alpha (PGF2 alpha) analogues – Fluprostenol and Cloprostenol, in mares at mid-pregnancy. It further assessed the variation in plasma progesterone concentration, which usually plays a critical role in pregnancy sustenance.

Experiment Design & Results

Three distinct experiments were carried out:

• In the first experiment, five mares at an average gestation length of 141.5 days were administered fluprostenol, an analogue of PGF2 alpha, both with intramuscular shots and later at regular intervals of 24, 48, or 72 hours. Despite a significant reduction in progesterone levels, there was no abortion.
• The second experiment featured the same five mares at least 10 days after the first experiment. This time, Fluprostenol was given via intravaginal and intramuscular routes, and the dosage was repeated after 48 hours. However, there were negligible changes in progesterone concentrations, and no pregnancy was terminated.
• The third experiment involved six mares at an average gestation period of 162 days. They received the other analogue of PGF2 alpha, Cloprostenol, at regular intervals of 6 or 12 hours until the fetus was expelled, signifying successful abortion. In this case, the progesterone concentration exhibited a significant decrease, both prior to and following the fetal expulsion. It took four days post-abortion for the levels to remain at a minimum. However, only one of six mares exhibited estrual (relating to the sexual cycle) behaviour post-abortion.

Takeaway from the study

The study concludes that PGF2 alpha analogues significantly influence the progesterone concentration in mares at mid-gestation but not enough to trigger abortions consistently. Further, even successful abortions (as obtained in the third experiment) did not prompt estrual behavior in the majority of the mares. The results suggest the analogues’ limited efficacy as abortifacients and its potential impact on the mares’ hormonal behavior thereafter. This indicates the need for further research to establish effective and predictable aborting methods in equine pregnancy management.