Equine Reproduction: Seasonality, Endometritis, and Twinning in the Mare
Authors: A. Trundell David
Journal: Equine Science
Summary
# Editorial Summary: Equine Reproduction—Seasonality and Clinical Challenges Natural photoperiod responses remain central to mare reproductive efficiency, yet the standardised breeding season definition often misaligns with individual mares' physiological peaks, creating management friction between natural cycles and competition calendars. David's review examines the multifactorial disruptions to cyclicity, including persistent corpus luteum function, behavioural suppression of oestrus, endometritis-induced subfertility, multiple ovulation events, and granulosa cell tumours—each presenting distinct diagnostic and therapeutic challenges. Understanding these conditions is particularly relevant given that endometritis represents a leading cause of reduced conception rates in breeding mares, whilst spontaneous persistent luteal function and behavioural anoestrus may be misdiagnosed as simple seasonal quiescence without appropriate ultrasonographic or hormonal investigation. The implications for practice centre on individualised breeding season planning based on mare phenotype rather than calendar dates, routine endometrial assessment before breeding, and recognition that seemingly non-responsive mares often require targeted interventions rather than simple rest. Coordinated management across vets, nutritionists, and handlers—adjusting lighting protocols, improving forage quality, and managing psychological stressors—offers the best approach to optimising reproductive outcomes throughout the year.
Read the full abstract on PubMed
Practical Takeaways
- •Plan breeding programmes with awareness of natural seasonal reproductive patterns rather than relying solely on artificial breeding season definitions to optimise fertility outcomes
- •Screen mares for endometritis and monitor for multiple ovulation as these are preventable causes of reduced reproductive efficiency
- •Consider psychological and behavioural factors alongside physical pathology when investigating cycling abnormalities, as stress and behaviour influence reproductive performance
Key Findings
- •Seasonality is a major influence on mare reproductive efficiency, with maximum efficiency not coinciding with the artificially defined breeding season
- •Endometritis and multiple ovulation are key abnormalities affecting reproductive performance in mares
- •Psychological influences and spontaneous persistent luteal function can disrupt normal oestrous cycling
- •Granulosa cell tumours and post-pregnancy failure behaviours contribute to reproductive dysfunction in mares