Changes in maternal androgens and oestrogens in mares with experimentally-induced ascending placentitis.

The research revolves around creating an additional diagnostic tool for detecting early stages of placentitis, an inflammatory condition of the placenta in horses, by examining the changes in maternal hormone levels. The study concludes that in mares suffering from this condition, there are significant decreases in oestrogen levels, while no significant changes in androgen levels are observed.

Objective and Methodology

• The primary objective of this study is to understand the changes in maternal hormone levels including dehydroepiandrosterone sulphate (DHEA-S), testosterone, estradiol 17-β (estradiol), and oestrone sulphate (OES) in mares with and without placentitis.
• The research included two parts – Study 1 (examining mares undergoing normal pregnancies to understand the typical hormone pattern) and Study 2 (comparison of hormone concentrations between pregnant mares with and without induced placentitis).
• In Study 1, blood samples were collected from healthy mares from 100 days of gestation to term. Longitudinal data from these samples helped establish baseline hormone patterns in normal pregnancies.
• In Study 2, subjects were split into two groups – one with induced placentitis and the other as a control. These pregnant mares were between 260-280 days into their gestation period. Placentitis was induced by an intracervical inoculation of Streptococcus equi ssp. zooepidemicus.
• Blood samples were collected at the start and then daily for 12 days post-inoculation for hormone analysis. The hormonal comparisons were also evaluated with respect to the days from abortion (DFA).

Findings and Conclusion

• In Study 1, a pattern was observed where DHEA-S peaked by 180 days of gestation, while testosterone increased progressively from Days 100 to 180, plateaued until around day 240, and then gradually declined until day 290 of gestation.
• Results from Study 2 showed that DHEA-S and testosterone levels did not significantly vary between healthy mares and those with induced placentitis.
• Significant changes over time, however, were observed in oestrogen levels, with estradiol and OES decreasing significantly in mares with placentitis. Particularly, estradiol levels reduced significantly at -6, -2, -1, and 0 DFA, while OES levels dropped significantly on the day before abortion.
• The research concludes that while testosterone and DHEA-S levels fluctuate during pregnancy, oestrogen levels (estradiol and OES) significantly decrease in mares with experimentally-induced ascending placentitis, offering a potential diagnostic marker for early detection of the condition.