Your cart

Your cart is empty

Understanding Horse Supplements for Moody, Hormonal Mares

Understanding Horse Supplements for Moody, Hormonal Mares

Understanding Horse Supplements for Moody, Hormonal Mares

Hormonal Balance in Mares

Like humans, horses can experience hormonal imbalances that manifest in various ways, including moodiness or unpredictable behavior. For mares, these imbalances can be particularly challenging, potentially affecting their overall health and performance. This is where horse supplements come into play, providing essential nutrients and compounds to support hormonal balance and manage mood-related issues.

Estrogen and progesterone are two of the primary hormones that regulate the reproductive cycle in mares and have a significant influence on their behavior and overall health.


Estrogen is a class of hormones that are produced in the ovaries and adrenal glands. The main types of estrogen in horses are estradiol, estrone, and estriol. Among these, estradiol is the most potent and is responsible for many of the physical changes seen in mares during their estrous cycle, such as the development of secondary sexual characteristics and the preparation of the uterus for pregnancy.

During the mare's estrous cycle, the levels of estrogen rise and fall. They are typically low during the winter months (anestrus period) when the mare is not cycling. As daylight hours increase in the spring (estrus period), estrogen levels rise, triggering a series of events leading to ovulation.

Behaviorally, high levels of estrogen are associated with "heat" behavior, such as frequent urination, 'winking' of the vulva, and increased interest in stallions.


Progesterone is another hormone produced in the ovaries, specifically in the corpus luteum after ovulation. Progesterone prepares the mare's uterus for pregnancy and helps maintain pregnancy if conception occurs. It suppresses estrus behavior and inhibits the mare from coming back into heat.

In the absence of pregnancy, the corpus luteum degenerates after about 14 days, causing progesterone levels to fall. This drop in progesterone levels signals the start of a new estrous cycle.

Behaviorally, high progesterone levels are associated with a lack of receptiveness to stallions and a decrease in "heat" behaviors. If a mare is unusually aggressive or moody, it could indicate low progesterone levels.

Role of Nutrition in Managing Equine Hormone Balance

The Importance of Nutritional Support for Moody Mares

Just as with human health, a mare's hormonal health is heavily influenced by her diet. Certain nutrients, such as magnesium and Vitamin E, are crucial for proper hormonal function. A deficiency in these nutrients can result in hormonal imbalances that can manifest as moodiness, irritability, or other behavior changes. Conversely, providing a nutritionally balanced diet can support a healthy hormonal balance, promoting overall wellness and reducing mood-related issues.


The Effect of Horse Supplements

Horse supplements designed for hormonal balance often contain key nutrients and herbs known for their hormone-regulating properties. They work by providing the necessary compounds for hormone production and regulation, supporting the body's natural processes. Key ingredients to look out for in such supplements include chasteberry (Vitex agnus-castus), which supports pituitary gland health, magnesium for its calming effect (more on this below), and raspberry leaf for its benefits to the reproductive system. 

Calming supplements, such as valerian, chamomile, and dandelion, can support the nervous system, stabilising a mare's temperament and helping to relieve mood swings. Chaste tree berry, commonly known as chasteberry, is used to help maintain normal hormone levels, support the endocrine system, and regulate metabolic function. In addition to supporting your mare’s overall wellbeing, these supplements also come in convenient forms like pellets. Some supplements even contain ingredients like milk thistle and dong quai, which can support a healthy tract system and aid in soothing cramps.

It's important to note that there is very little academic research on the use of these herbal supplements for mares, however there are many horse owners that swear by them. Given the low cost of these supplements, it may be worth experimenting to see if any of these helps your mare. 

Feeds to Avoid

Some feeds have phytoestrogens or plant-derived compounds that mimic estrogen in the body. They are found in various feeds and forages and, in excess, can cause hormonal disruptions. Always ensure that your horse's diet is balanced and doesn't overly rely on high-phytoestrogen feeds. Two commonly fed feeds with phytoestrogens are soy and alfalfa. We recommend reducing your horse's consumption of these two feeds and seeing if that improves your mare's behavior during heat cycles. Geldings can also be effected by phytoestrogens so if your normally well-behaved horse is exhibiting a change in temperament or behaviour, consider avoiding these feeds. 

Magnesium Calming Supplements

Role of Magnesium

Magnesium is a crucial mineral for a myriad of biological functions, including hormonal regulation. Although often overlooked, its role in hormone balance is fundamental to both human and animal health, including horses.

One of the most important roles of magnesium is as a cofactor for a variety of enzymes. This means that many biochemical reactions in the body require the presence of magnesium to proceed. In fact, it is involved in over 300 enzymatic reactions in the body, including those that produce and metabolize hormones.

Hormones, such as insulin, thyroid hormones, estrogen, progesterone, and testosterone, all depend on magnesium for their production, function, and regulation. Magnesium aids in the release of hormones, enhances their function, and helps regulate their levels in the body.

In the context of equine health, magnesium also plays a role in maintaining normal nerve and muscle function, supporting a healthy immune system, and promoting a steady heart rhythm, all of which can indirectly influence the horse's hormonal system. Magnesium can have a significant impact on hormone balance. Magnesium deficiency can lead to a variety of symptoms and health issues, many of which may be attributed to its role in hormone production and function.

One area where magnesium has shown particular importance is in managing stress and nervousness in horses. Magnesium helps regulate the hormone cortisol, often referred to as the "stress hormone." By regulating cortisol levels, magnesium can help manage stress responses in horses, contributing to calmer, more predictable behavior. Additionally, magnesium plays a role in insulin regulation, which is critical for horses at risk of insulin resistance, a hormonal condition that can lead to equine metabolic syndrome.

Magnesium's Effect on Estrogen and Progesterone 

Magnesium is involved in the metabolic pathways of estrogen. It helps with the proper function of enzymes needed for the biosynthesis and metabolism of estrogen. Magnesium deficiency can, therefore, affect estrogen levels in the body, leading to hormonal imbalances.

In humans, studies have suggested that adequate magnesium levels may help manage symptoms associated with premenstrual syndrome (PMS), which is thought to be linked to fluctuations in estrogen levels. While more research is needed, particularly in horses, it's plausible that magnesium may help manage behaviors associated with estrus in mares, often referred to as a mare being "in heat."

Magnesium is also crucial for the production and regulation of progesterone. It plays a role in the function of the corpus luteum, the structure in the ovary that produces progesterone after ovulation. If the mare becomes pregnant, the corpus luteum continues to produce progesterone, which is crucial for maintaining the pregnancy.

Additionally, in human studies, magnesium supplementation has been found to help alleviate symptoms of PMS, some of which are thought to be related to progesterone levels. This might suggest that magnesium can help regulate progesterone-related functions, though more specific research in horses is needed.


In the equestrian world, the term "moody mare" is often used to describe a female horse with unpredictable or challenging behaviour, often linked to hormonal imbalance. Understanding and managing these changes is key to maintaining a balanced temperament and promoting overall health in your horse.

This blog has shed light on the role of supplements in supporting hormonal balance, particularly focusing on mares. Utilizing key substances such as magnesium, chasteberry (Vitex agnus-castus), and other calming ingredients found in equine supplements, like "mare magic," may help support normal hormone levels and alleviate moodiness.

Magnesium, for example, plays a crucial role in over 300 enzymatic reactions, some of which are directly linked to the production and regulation of hormones like estrogen and progesterone. Other elements like zinc, manganese, and iodine also aid the endocrine system, crucial for hormone regulation.

Of course, we always recommend consulting your equine nutritionist before introducing any new supplement into your horse's diet. If your mare or gelding shows signs of colic, behavioural changes, or tension, discontinue use and seek immediate veterinarian assistance.

From breeding to everyday riding, maintaining your mare’s hormonal balance and temperament is crucial. With proper nutritional support, you can help to rebalance their system, promote a more predictable disposition, and enjoy a happier, healthier equine experience.


1 comment

  • Cari

    What do you recommend giving a moody mare? Supplements? I have her on regumate has maybe helped some but she still backs her ears and kicks in stall at other horses😩 any tips so appreciated
    Thank you Cari

Leave a comment