Chastetree Berry: Magic for Moody Mares or a Waste of Money?

If you're a mare owner, you will be familiar with the problems associated with the oestrus cycle during springtime. As the days draw out and the weather changes, mares experience a transitional season where their oestrus cycle begins again after being dormant all winter. If you're interested in learning more about the oestrus cycle and why mares display such extreme behavioral characteristics related to their hormone levels, review our article on moody mares . Mare owners are regularly on the lookout for a supplement which could be added to their horse’s diet to help manage behavioral symptoms in mares. One such herbal ingredient which has been suggested to positively impact a mare's moods is Chastetree berry. But, what is this herb and how precisely does it help?

Mares can be unpredictable due to their oestrus cycle*

Unmanageable mares;

The oestrus cycle in mares is, of course, essential to regulate ovulation and preparation of the uterus for pregnancy. It does not matter whether your mare is being used for breeding or not, she will still cycle and experience the hormonal changes associated with that cycle. These hormonal surges can trigger behavior in mares which can be difficult for owners to handle.

Signs can include;
- Aggression
- Abdominal cramping
- Lack of interest in food
- Unpredictable behavior around other horses, particularly male horses or youngsters

- Kicking out, biting and lack of interest in other horses.
- Unusually stubborn behavior
- Decline in performance under saddle or in hand
- Back Soreness issues
- Clinchy/ Girthy-Meaning the horse becomes hostile when the girth is tightened.

Not only can these signs make riding difficult, but basic everyday tasks such as catching your horse, handling her around other horses safely and turning her out can present serious challenges.

Supplement solution?

Many owners turn to supplements to try and regulate the signs of the oestrus cycle. Most of these are based either on magnesium for the calming effect or herbs that are renowned for impacting hormone levels. One of the most reputed herbs is called Chastetree Berry - also known as Monk’s Pepper, Abraham’s Balm, Tree of Chastity, Wild Lavender or Poire Sauvage.

The Chastetree is a small bush which grows in the Mediterranean and Asia. The fruits of the tree - the berry - look like pepper berries and are either dried or turned into a liquid or infusion.

What Are the Benefits of Chastetree Berry?


The Chastetree Berry has been used in human herbal medicine for centuries. References can be found in older manuals where the Chastetree Berry is recommended for use as a sedative, a contraceptive and strangely enough, as an aphrodisiac! It was thought that the one of the names given to the herb, "Monk’s Pepper" refers to its usage by monks throughout the middle ages as a tonic to reduce their libido!

Today, Chastetree Berry's main use is in hormone regulation in females: this ranges from menstrual disorders to hormone related acne and eczema, infertility and hot flushes related to menopause.  This has led equine herbalists to suggest that Chastetree Berry can be beneficial in balancing hormones in mares, helping to relieve some of the more dreaded aspects of high-strung mare misbehavior.

Does it Actually Work?

Some studies suggest that, in fact, Chastetree Berry does influence hormone levels. (Wuttke W, Jarry H, Christoffel V, Spengler B, Seidlova-Wuttke D. Chaste tree (Vitex agnus-castus)-pharmacology and clinical indications. Phytomedicine 2003;10(4):348-57.) Studies carried out in rats have revealed raised progesterone levels when supplemented with the herb. This is useful, as progesterone works to relieve the symptoms of pre- menstrual syndrome and menstrual cycle abnormalities. Chastetree Berry is among the most highly sought after herbs given its perceived ability to help minimize hormonal issues.  Despite any solid evidence, it is clear that feeding Chastetree Berry supplement is not harmful for healthy mares, however, due to the perceived properties it must NEVER BE FED TO PREGNANT MARES. If you own a mare who's a handful when she's in season, talk to your veterinarian about the pros and cons of using Chastetree Berry to help keep her more manageable.

*Images courtesy of Dollar Photo Club