The average gestation length in the mare ranges from 320 to 362 days; most mares will foal within 330-345 days of successful breeding. Ponies, on average, tend to have shorter gestation periods than full-size horses.
If you want to determine when your pregnant mare will foal click the link below for a neat online calculator:
https://thehorse.com/tools/mare-gestation-calculator/?_token=26f97f0c2d&answer%5B4%5D=10#
Mares typically cycle regularly between April and early September. For a few months on either side of that, the ovaries are in the process of either gearing up for spring or slowing down for winter and may produce one or multiple follicles at irregular times. During these spring and fall transition periods, the mare may or may not show signs of being in season. Reproductive behavior is most likely to be noticed during the fertile period between April and September.
Signs that a mare is in season include:
- holding the tail elevated,
- "winking" (opening and closing) the lips of the vulva
- variable amounts of squatting and squirting of urine and mucus.
- her level of activity usually slows down a bit,
- she often seems preoccupied and it is more difficult to get and hold her attention
- often for the first few days they begin showing signs, some mares are very irritable and sensitive to touch
- she may threaten to kick or even bite.
While there is nothing you “need” to do during your mare’s season, there are things you can do to help her during the time hormonal changes are taking place. Part of the change in your mare’s behavior during season is due to hormonal changes that are making her focus elsewhere. You may notice that because your mare is focused elsewhere, she may be more easily startled. In addition to your mares focus being elsewhere, the pressure-like pain from the enlarging follicle and/or pulsations in the ducts that will carry the egg to the uterus she may be experiencing some pain and irritability.
Things you can do to help your mare during season include:
- Avoid approaching your mare from behind.
- Begin grooming at her neck and shoulders before working back to the sensitive flanks.
- Ovulation can produce pain, so give the mare some Banamine for a day or two if her if you suspect the pain is extreme. Talk to your veterinarian if Banamine does not alleviate her discomfort.
- Try to interrupt the heat-cycle symptoms only during work or riding sessions.
- Don't punish your mare for being preoccupied during her season and try to work with her.
- Concentrate on telling her what you want her to do, and avoid scolding her for behavior you don't want.
- Don't expect her to completely shut down her strong hormonal drives just because you'd like her to.
- Consider focus-type lessons, such as ground poles, jumping combinations, frequent changes of gait direction and speed.
If you really need something to control your mare's seasons there are supplements which use different herbs, including many calming ingredients that may be worth trying. Happ-E-Mare contains natural herbs in a great-tasting proprietary blend of eleuthro, ashwagandha, raspberry leaf, chastetree berry, ginger, oregano, arginine, spirulina, MSM, boswellia and chia; added vitamins (2,024 IU vitamin E, 2 mg vitamin B6) and added minerals (560 mg magnesium oxide). Gluten-free. Non-GMO/Certified herbicide-free (includes glyphosate). No artificial colors. Certified melamine-, pesticide-, lead- and drug-free, and low in sugar, starch and fructan. Another option to consider would be Mare Magic is a calming supplement that also contains raspberry leaf, and additionally bolsters a sound regenerative framework in female horses.