Prolonged interovulatory interval after oestradiol treatment in mares

Area of Science:

• Reproductive biology
• Veterinary medicine
• Endocrinology

Background:

• Luteolysis, the regression of the corpus luteum, is a critical event in the oestrous cycle of mares.
• Understanding factors that regulate luteolysis is essential for reproductive management in horses.

Purpose of the Study:

• To investigate the potential of estradiol-17 beta administration to prevent or delay luteolysis in mares.
• To assess the effects of varying estradiol doses on the timing of luteolysis and subsequent reproductive events.

Main Methods:

• Mares were administered daily doses of 0, 0.1, 1.0, or 10.0 mg of estradiol-17 beta from ovulation until the subsequent ovulation or for up to 32 days.
• Luteolysis was monitored by tracking the lifespan of the corpus luteum.
• Follicular growth and ovulation were also observed during the treatment period.

Main Results:

• Estradiol treatment did not significantly alter the timing of luteolysis, with corpora lutea regressing between 15.8 and 17.3 days post-ovulation across all treatment groups.
• Estradiol administration did not affect oestrous behaviour following luteolysis.
• Daily treatment with 10.0 mg of estradiol-17 beta effectively suppressed follicular growth and prevented ovulation.

Conclusions:

• Estradiol-17 beta is ineffective in preventing or delaying luteolysis in mares.
• High-dose estradiol treatment exhibits a significant inhibitory effect on follicular development and ovulation in mares.
• Further research may explore alternative hormonal strategies for modulating luteolysis or follicular dynamics in mares.