Periovulatory changes in peripheral plasma progesterone and estrogen concentrations in the mare

Area of Science:

• Reproductive endocrinology
• Veterinary medicine
• Equine science

Background:

• Hormonal fluctuations significantly influence reproductive cycles in mares.
• Understanding periovulatory hormone dynamics is crucial for reproductive management in horses.

Purpose of the Study:

• To precisely measure progesterone and estrogen concentrations in mares around the time of ovulation.
• To correlate hormonal changes with the ovulatory event in equine reproduction.

Main Methods:

• Peripheral blood plasma samples were collected from mares every 2 hours.
• Sampling occurred from 36 hours before to 26 hours after ovulation.
• Hormone concentrations were determined using radioimmunoassay techniques.

Main Results:

• Progesterone concentrations remained stable (60-100 pg/ml) from 24 hours before to 8 hours after ovulation.
• Post-ovulation, progesterone levels significantly increased, reaching 140 pg/ml by 10 hours and 346 pg/ml by 26 hours.
• Plasma estrogen concentrations exhibited no significant alterations throughout the study period.

Conclusions:

• Progesterone exhibits a distinct surge following ovulation in mares.
• Estrogen levels are not significantly correlated with the immediate periovulatory period in mares.
• These hormonal profiles provide insights into equine reproductive physiology.