Female: reproductive cycle - normal

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  • The mare is seasonally polyestrus 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 oestrus 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: 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.
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