Luteoprotective role of equine chorionic gonadotropin (eCG) during pregnancy in the mare.

The research article investigates how the hormone equine chorionic gonadotropin (eCG) influences pregnancy in horses, specifically its role in protecting against the effects of another hormone, PGF2α, which can disrupt pregnancy. It was observed that the level of eCG also impacts the time required for completion of luteolysis, foetal death and foetal expulsion.

Objective of the Study

• The aim of the study was to compare the effects of administering cloprostenol, a synthetic analog of PGF2α, in horses impregnated by other horses and in horses impregnated by donkeys.
• The main goal was to understand the role of eCG in the development of pregnancy-associated resistance to the luteolytic and abortifacient effects of PGF2α.

Methodology

• The study was carried out with a sample of twenty horses; eleven were impregnated by donkeys and nine by horses.
• Some of these pregnant horses were injected with cloprostenol at specific intervals, while the rest served as controls.
• The researchers then compared the concentration of eCG and the time required for completion of luteolysis in the two sets of pregnancies.

Findings

• The results showed that eCG concentrations were ten times higher in horses impregnated by other horses compared to those impregnated by donkeys. This difference was not influenced by the administration of cloprostenol.
• Luteolysis was completed faster in horses with mule pregnancies compared to those with horse pregnancies.
• There were significant correlations between the eCG concentrations at the beginning of the experiment and the time required for completion of luteolysis, foetal death, and foetal expulsion.

Conclusion

• The study suggests that high eCG concentrations in mares impregnated by horses protect the corpora lutea, a structure critical for pregnancy, against the luteolytic effects of PGF2α.
• On the other hand, mares carrying mule foetuses have low eCG concentrations, which affords them less protection against the luteolytic effect of PGF2α. This could potentially explain the increased foetal mortality observed between days 60 and 90 of pregnancy in these mares.