Normally good-natured, obedient, and willing, changes in hormone levels can turn your darling horse into an unpredictable, grouchy nightmare! While some mares barely change during their season and are able to be ridden and handled as normal, others really suffer, showing signs of discomfort and changes in personality. Some of these issues, such as raising the tail, urinating frequently, and ‘winking’, represent the mare's desire to breed, showing the males that she is receptive to their advances. These behaviours are usually coupled with a lack of concentration, and your mare being less willing to cooperate: her mind is on other things! Some mares will also show behaviours such as kicking, biting, and squealing.
Understanding the mare's reproductive system
Most mares are seasonally polyoestrous, which means that their reproductive cycles depend on the time of year, with the mare’s breeding season typically covering the months between March and October. Daylight hours are primarily what regulates a mare’s reproductive activity, and the pituitary gland is responsible for producing the hormones that stimulate the increased ovarian activity in the spring.
During the winter time, the mare will be in a non-reproductive season known as ‘anoestrus’ when her ovaries are inactive, and it is unlikely she’ll display any ‘mare-ish’ behaviour. This is because a mare’s gestation period is 11 months, so naturally a mare won’t cycle over the winter months in order to avoid foaling at a similar time a year later when the weather is likely to be very challenging for a newborn foal.
The average length of the mare’s oestrus cycle is 21 days, and the mare is typically in season for 5-7 days, and behavioural issues will become worse as the ovarian follicles increase in size and higher levels of oestrogen are produced. The rise in oestrogen levels triggers the mares to release an egg, which usually happens during the last 2 days of oestrus. Once the egg is released, the mare starts producing more progesterone, the hormone that prepares the uterus for pregnancy. This stage is known as dioestrus and lasts around 14-16 days. At this point, the mare will no longer be receptive to the stallion. If the mare is not covered or is covered unsuccessfully, hormonal changes reverse the changes to the uterus and start the cycle again.
Why don’t mares cycle all year round? And why some mares do!
The gestation time (period that the female is pregnant) for a horse is 11 months, so the mare will not usually cycle over the winter in order to avoid having a foal during the months when the weather is likely to be bad. Most mares will start cycling in the early spring, typically in March or April, and this will continue throughout the summer until October or November. This cycling is largely dependent on daylight hours, and mares can also be affected by artificial lighting - which can be used to bring them into season.
Top tips to manage your mare when she is in season:
- If your mare gets sensitive when she is in season, try to plan competitions, lessons, or outings avoiding these few days.
- For the couple of days when your mare’s behaviour is at its worst, it may be worth giving her a couple of days off, or doing low-stress work - neither of you will enjoy a constant battle.
- Feeding certain herbs can help control your mare's oestrus-related behaviour during the spring and summer, providing a natural way of maintaining hormonal balance and keeping both you and your mare safe and happy!
My mare is a pain all year round - and it doesn’t seem to be affected by seasons, what should I give to her?
To check to see if your mare’s behaviour is dictated by season, try keeping a diary to show you any patterns. If the behaviour is worse on similar days during her season, and this occurs on a 3-weekly basis, it is likely that hormones are causing the bad behaviour, and you should follow the tips above. If the behaviour doesn’t seem to be cyclical, we recommend you look for another cause- checking to see if your horse is in pain, if their diet needs adjusting, or if you could handle them differently to help them to cooperate.
What else could be causing your mare's grumpy behaviour?
Your mare may be displaying undesirable behaviour for reasons other than her hormonal changes. It is useful to consult your vet, who will perform a physical examination to rule out any other underlying issues that may have similar symptoms. These could include back pain, gastric ulcers, lameness, or urinary tract infections to name a few, and all of which require specialised treatment. A healthy, comfortable horse is a happy one, so it is important to seek advice if you are at all concerned about your horse.
If you have any questions, our Registered Nutritionist will be more than happy to help! Call 0800 585525, email [email protected], use the live chat function on our website, or send us a DM on social media.
