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The oestrous cycle of the mare
Journal of Reproduction and Fertility. Supplement
|October 1, 1975
Summary
This study details equine reproductive cycles in non-pregnant mares, revealing variations in oestrus duration and ovulation timing. A significant finding is the occurrence of ovulation without observable oestrus in several mares.
Area of Science:
- Veterinary Science
- Animal Reproduction
- Equine Studies
Background:
- Understanding the equine oestrous cycle is crucial for effective breeding management.
- Variations in cycle length, oestrus duration, and ovulation patterns can impact reproductive success.
Purpose of the Study:
- To characterize the oestrous cycle parameters in non-pregnant mares.
- To investigate the relationship between oestrus, ovulation, and dioestrus.
- To identify any unusual reproductive syndromes in mares.
Main Methods:
- Longitudinal study over 2 years involving eleven non-pregnant mares.
- Monitoring of oestrous cycle length, duration of oestrus, and ovulation timing.
- Palpation of the corpus luteum (CL) and measurement of follicular diameter.
Main Results:
- Average oestrous cycle length was 20.6 days; oestrus duration varied seasonally (longer in Feb-May).
- Most ovulations occurred overnight (16:00-08:00), with 78% within 48 hours of oestrus cessation.
- Ovulation without oestrus was observed in 6/11 mares, and a syndrome of prolonged CL without oestrus occurred in 6 mares.
Conclusions:
- Equine oestrous cycles exhibit considerable variability, influenced by season and individual mare factors.
- Ovulation can occur independently of external oestrus signs, a phenomenon observed frequently.
- A distinct syndrome of prolonged luteal activity without oestrus requires further investigation for reproductive implications.