Prolonged interovulatory interval after oestradiol treatment in mares.

This research examined whether treating horses with oestradiol would impede luteolysis – the breakdown of the corpus luteum. The study discovered that while it does not prevent luteolysis, treating with high doses (10 mg) of oestradiol can impede ovulation and the growth of ovarian follicles.

Objective of the Research

• The investigation’s aim was to establish whether oestradiol treatment can prevent or delay luteolysis in mares.

Methodology

• The investigators grouped the mares into five groups, each containing five horses. The treatment began on the day of ovulation and lasted till the day of the next ovulation or for a maximum of 32 days.
• The treatment involved administering oestradiol-17 beta, with doses varying by group: 0, 0.1, 1.0 or 10.0 mg.

Key Findings of the Study

• The study found that the treatment with oestradiol could not avert luteolysis, regardless of the administered dose. Luteolysis occurred approximately 15.8 to 17.3 days after the previous ovulation for all the groups, indicating that the oestradiol treatment had no noticeable effect on delaying luteolysis.
• While the oestradiol treatment was unable to change oestrous behavior after luteolysis, the daily administration of the highest dose (10.0 mg) of oestradiol resulted in the stunting of follicular growth and suppression of ovulation.

Implication of the Research

• The results suggest that high doses (10.0 mg) of oestradiol can be used to prevent ovulation in mares and inhibit follicular growth.
• This is particularly important in horse breeding and could potentially affect the timing and control of equine reproduction.