Treatment with human chorionic gonadotrophin before ovulation increases progestin concentration in early equine pregnancies.

The research article discusses a study on the effects of treating horses with human chorionic gonadotropin (hCG) before ovulation and its impact on progestin levels and early pregnancy development. The study found that hCG treatment increases progestin concentration, contributing to a better maintenance of early pregnancy.

Study and Methods

• This study aimed to understand the effects of hCG treatment on horses either before ovulation or during the early luteal phase. The primary metric for gauging the treatment’s success was the level of progestins — hormones crucial for the early stages of pregnancy.
• Human chorionic gonadotropin is a hormone that can induce ovulation in horses, and it has been found to stimulate the synthesis of progesterone, an essential progestin, in cattle.
• The researchers performed two experiments to investigate the influence of hCG treatment. Both exercises measured plasma progestin concentrations, the size of the corpus luteum (a temporary endocrine structure involved in ovulation and early pregnancy), and the size of the conceptus (the developing embryo, including all extra-embryonic membranes) in pregnant mares.

Findings

• Experiment 1 found that inducing ovulation with hCG significantly increased the concentration of progestins between days 5 and 15 after ovulation, compared to untreated controls.
• The study also observed a significant interaction between hCG treatment and the size of the conceptus between days 30 and 40 of pregnancy, suggesting that the hormone might stimulate conceptus development.
• On the other hand, Experiment 2 showed that hCG treatment on day 5 after ovulation didn’t affect progestin secretion or the area of luteal tissue, compared to untreated mares.

Conclusion

• The findings indicate that treating mares with hCG to induce ovulation within 48 hours before ovulation, but not on day 5 of the luteal phase, can enhance progestin secretion.
• This increase in progestin might enhance the development of the conceptus through the stimulation of endometrial function during early pregnancy, potentially preventing early conceptus loss which is a common issue in equine pregnancies.