At this time of year mare owners are often reminded that their horses and ponies are still entire, unlike geldings. Mares are at the mercy of their endocrine systems, which drive maternal and breeding behaviour. Many mare owners find their mares more difficult during times of active cycling, and behaviourists have described their behaviour as ‘awkward and recalcitrant’.

The mare’s oestrous phase is around 7 days on average, in a three week cycle, and takes place through the spring and summer in the Northern hemisphere. During this time she is receptive to the stallion and can be less easy to keep focused on what we want! Her behaviour will then change gradually as she enters what is described as the dioestrous period.

Mares can be quite expressive when actively cycling.
Mares can be quite expressive when actively cycling.

Reproductive behaviour is closely linked to social hierarchy, and in horses and most other mammals and birds, reproductive rates are higher for more dominant compared to more subordinate females. This link between reproductive and social behaviour helps explain why actively cycling mares can get so focused on other horses. Some mares might be more sensitive to touch, moody and irritable or appear to be in some pain or discomfort, rather like PMS in women.

There is wide variation in individual mare’s behaviour, with some hardly seeming affected at all, and others seeming at the complete mercy of their hormones. Of course, difficult or unwanted behaviour in mares might not be down to their hormones, and if it is present all the time, then it could be linked to pain or poor training instead.

Some owners choose to manipulate their mare’s behaviour with the use of chemical drugs, or intrauterine marbles, which can help them be more relaxed and focused on their sport. A good understanding of behaviour and training and how to keep a horse focused, regardless of their hormones will help a great deal with so–called mare-ish behaviour.

We should bear in mind that mares are entire so their hormones can affect their behaviour.
We should bear in mind that mares are entire so their hormones can affect their behaviour.

Vitex agnus-castus, or chasteberry, is widely used by women with premenstrual syndrome (PMS) and research studies have shown it to be effective in moderate to severe PMS. Chasteberry is the fruit of the chaste tree, and the berries contain a number of compounds including antioxidant flavonoids, irioids and essential oils. They affect brain chemistry and the female hormones involved in cycling, and these actions are believed to be why they are effective in treating PMS.

Whether or not this herb is as effective for mares has not yet been researched, but there are many anecdotal reports and it is likely that it works in the same way. It can be safely used in any mare who shows hormonal behaviours, particularly those who show irritable or moody behaviour.

This entry was posted in News, Top ten questions for spring by Clare MacLeod. Bookmark the permalink.

About Clare MacLeod

Clare MacLeod MSc RNutr is one of the UK’s few registered independent equine nutritionists who also has expertise in health and fitness. She advises private and commercial clients in all sectors of the horse world and is a hands-on horse owner herself. Clare is passionate about correct nutrition as a foundation for good health, without which peak fitness is not possible. She states “Good nutrition isn’t everything, but there’s nothing without it”.