Luteal vascularity and embryo dynamics in mares during early gestation: Effect of age and endometrial degeneration.

This study investigates the effect of age and endometrial degeneration on embryo development and luteal status in mares during the first 20 days of pregnancy. It was found that older and mares with significant endometrial degeneration exhibited larger total corpus luteum area but reduced luteal vascularity. Despite this, progesterone levels remained the same across all groups. The study also found an impact of age on embryonic vesicle diameter and mobility, with older age resulting in a reduction of the embryonic mobility and delayed embryo development, regardless of the extent of endometrial degeneration.

Study Overview

The main aim of the study was to investigate how age and endometrial degeneration affected the luteal status and development of the embryo in the first 20 days of gestation in mares. Factors such as the total area of the corpus luteum, progesterone concentrations and various aspects of embryo dynamics were measured and evaluated.

Methodology

• The mares were divided into different groups based on their age and the degree of endometrial degeneration. Young mares aged 6 years or less, older mares aged 15 years or more, mares with minor endometrial degeneration and mares with severe endometrial degeneration were studied.
• The total corpus luteum area, luteal vascularity, progesterone levels, embryonic vesicle diameter, number of embryonic location changes, and uterine contractility among other factors were evaluated throughout the 20 day period.

Findings

• Older mares and mares with severe endometrial degeneration had a larger total corpus luteum area but a lower luteal vascularity than their younger and mild degeneration counterparts.
• Notably, progesterone levels remained the same across all four groups, regardless of age or endometrial degeneration.
• The study also discovered that age negatively affected the embryonic vesicle diameter. However, the degree of endometrial degeneration did not have a significant impact on the embryonic vesicle diameter.
• Embryo mobility was high until day 14 of gestation in mares with severe endometrial degeneration, while older mares exhibited earlier reductions in the number of embryonic location changes.

Conclusion

The corpus luteum in older mares and mares with severe endometrial degeneration underwent structural remodelling in order to safeguard local blood supply and maintain continuous progesterone output during early gestation. Additionally, the study found that advanced age was associated with a decrease in embryonic mobility and a delay in embryo development, irrespective of the degree of endometrial degeneration.