Hormonal changes associated with induced late abortions in the mare.

This study examines the different hormonal changes associated with induced late abortions in horses. Two hormonal treatments, PGF-2 alpha and a combination of oestradiol benzoate and oxytocin, were tested on pregnant mares. The study finds that each treatment impacts different hormones and affects the course of abortion differently.

Experimental Procedure

• Researchers subjected four mares, each approximately 150 days pregnant, to two different abortion-inducing treatments. Two mares were given PGF-2 alpha twice daily, and the other two a combined treatment of oestradiol benzoate and oxytocin.
• The PG-treated mares aborted after 37 and 61 hours, respectively. The fetuses were expelled intact within their fetal membranes.
• Conversely, the mares treated with the combined oxytocin treatment aborted at 13 and 27 hours after the first injection. These mares experienced strong uterine contractions and expelled fetuses with disrupted fetal membranes.

Hormonal Changes

• Following both treatments, concentrations of 15-ketodihydro-PGF-2 alpha (a metabolite of the hormone prostaglandin F2 alpha) increased. However, after PG-induced abortion, this hormone quickly returned to its basal level, whereas, after oxytocin-induced abortion, the hormone concentrations significantly increased, suggesting damage to the uterus.
• Progesterone and relaxin, hormones related to pregnancy and placental function, diminished in association with the induced abortions.
• Oestrone sulphate levels behaved differently in the two treated groups. The mares with oxytocin treatment showed a rapid decrease, while those treated with PG first showed a notable increase and then a decrease.
• The concentrations of Pregnant Mare’s Serum Gonadotropin (PMSG), a glycoprotein hormone produced in the placenta of a pregnant mare, seemed to be unaffected by the abortions. This finding suggests that this hormone may not be directly invovled in the process of abortion.

Implications

• These findings can provide valuable insights into the various hormonal changes and physical outcomes associated with induced late abortions in mares. This could lead to better methods of managing reproductive health in mares.
• The differences observed in hormone levels indicate that the two methods of inducing abortion in mares have varying physiological impacts on the animals, warranting further research.