Some steroids in the blood of mares suffering from endometritis and post-partum mares as compared to normal cycling mares.

The study investigates the levels of certain steroids in the blood of horses experiencing post-partum and endometritis conditions, and compares them to levels in healthy, cyclic horses. It found that during early stages of heat, these horses typically have higher concentrations of pregnenolone, compound “5.4”, and progesterone. These concentrations often seem to decrease around two days before ovulation, matching those of healthy horses, and can influence ovarian activity.

Understanding the Sample and Conditions

• The research focused on mares, or female horses, suffering from endometritis – an inflammatory condition of the inner lining of the uterus – and those in the post-partum phase, as well as normal, cyclic mares.
• Hormonal fluctuations are a normal part of the estrous, or reproductive, cycle in mares. This research investigates potential abnormalities in the levels of certain hormones in these specific conditions.

Observations and Results from the Study

• The concentrations of pregnenolone, compound “5.4”, and progesterone in mares with endometritis were found to be significantly higher than in normal mares during the initial days of the heat period.
• However, these levels appeared to decrease after the first days of the heat period and were close to normal around two days before ovulation.
• Eight mares with severe endometritis had a prolonged estrous period and did not ovulate, with developing eggs in the ovaries becoming atretic, or failing to mature. The research suggests that the higher progesterone levels may be a contributing factor, potentially inhibiting follicular growth and extending the estrous period.

Insights into Post-partum Mares

• Similar hormonal patterns were observed in post-partum mares. Elevated levels of the hormones were found a few days after giving birth and during the ‘foal heat’, or first estrous cycle after pregnancy, in four out of eight mares.
• This was thought to be potentially due to uterine infection or stimulation.

Proposed Hypothesis and Significance

• The research proposes the hypothesis that progesterone from the uterus can influence ovarian activity. This hormone could be one of the factors posing a risk for periods of infertility, or anoestrus, in horses with endometritis or post-partum mares.
• If proven correct, this finding could have significant implications for how these conditions are managed in the world of horse breeding and animal science.