Equis ISSN 2398-2977

Female: reproductive cycle - normal

Synonym(s): Normal reproductive cycle in the female

Contributor(s): Wendy E Vaala, Terry Blanchard, Madeleine L H Campbell

Introduction

  • The mare is a seasonally polyestrus, long day breeder, exhibiting a distinct breeding season during the spring, summer and early autumn.
  • Approximately 75-80% of mares in the northern hemisphere are seasonally polyestrus, whilst up to 25% (higher in Arabian mares Arab and in latitudes closer to the equator) are truly polyestrus and have estrus cycles year round.
  • During the breeding season mares show repeated estrus cycles (ovulation to next ovulation) of 21 days.
  • The estrus cycle is a series of synchronized interrelated events involving changes in the anatomy, endocrinology and behavior of the mare Behavior: aggression - hormone related    Behavior: maternal  → ovulation.
  • This includes 4-7 days (variation: 2-12 days; affected by the time of year - longer early in breeding season) of estrus when the mare is receptive to the stallion.
  • Following estrus is diestrus, usually 16-17 days (relatively constant throughout the year), when the mare rejects the stallion.
  • During the winter most non-pregnant mares experience a period of anestrus when they are sexually inactive and respond in a neutral manner to the stallion.

Seasonal effects - 'seasonality'

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Anovulatory or anestrus phase

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Transitional phase

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Ovulatory phase

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Further Reading

Publications

Refereed papers
  • Recent references from PubMed and VetMedResource.
  • MacPherson M L & Blanchard T L (2005) Breeding mares on foal-heat. Equine Vet Educ 17 (1), 44-52 VetMedResource.
  • Pycock J F (2003) Encouraging early cycling in the mare. UK Vet 8 (1), 4.
  • Britton B A (1982) Endometrial change in the annual reproductive cycle of the mare. J Repro Fertil Suppl 32, 175-180 PubMed.
  • Colquhoun K M, Eckersall P D, Renton J P & Douglas T A (1987) Control of breeding in the mare. Equine Vet J 19 (2), 138-142 PubMed.
  • Allen W E (1979) Abnormalities in the oestrous cycle in the mare. Vet Rec 104 (8), 166-167 PubMed.

Other sources of information

  • Ginther O J (1992) Reproductive Biology of the Mare: Basic and Applied Aspects. 2nd edn. Equiservices, Cross Plains, WI, USA. ISBN: 9780964007215.


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