By Suzie Middlebrook, BSc

Horses are reactive, flighty, and anxious creatures and for good reason. In the wild, a horse’s best defense is his ability to respond quickly and effectively to his surroundings. Unfortunately, these same characteristics are often contradictory to what is desired in an ideal riding horse. While training, exposure, and breeding can help produce a calmer and more reliable mount, sometimes a combination of management and nutritional strategies must be employed to get the best results when working with a hot horse. This is particularly true with young horses, mares, and stallions. It is also important to note that there are different types of “hot” behavior. One would employ a different combination of strategies for an anxious youngster on his first trip off the property than one would for an overly enthusiastic hunter. Often times, it takes a good deal of testing different tactics to find the best combination for an individual horse.

From a management perspective, there are a variety of strategies that one may employ. For example, it is ideal that every horse have access to some sort of turn-out daily and this is particularly true for a high strung horse. When away from home, a ride or lunge a few hours before your class or clinic should help the horse settle when turn-out isn’t available. For youngsters and inexperienced horses, the best strategy is often just having lots of exposure in a variety of situations without the added stress of horse show nerves. Some examples of low stress exposures would be clinics, foxhunting, or even cattle wrangling.

From a nutrition standpoint, it is often best to examine the full ration that your horse is receiving and identify if any of these components may be inadvertently causing the undesirable behavior. It is also important to note that a nutritional solution for one horse may not be the best answer for another. Particularly in the realm of calming solutions, there is no one perfect ration for every hot horse and a horse owner should always be willing to experiment to find out the best answer for one’s individual horse.

In general, a diet low in simple sugars and protein is best for managing excess energy levels. A feed high in simple sugars can cause a large glycemic response, i.e. a large and rapid increase in blood sugar levels. Some examples of feeds with a high glycemic index would be oats, sweet feed, or a feed designed for high energy performance horses. While alfalfa hay is something that many horse owners are told to avoid for hot horses, this is usually only an issue for horses that are being fed alfalfa as the majority or entirety of their hay ration. A small flake of alfalfa for lunch will rarely cause obvious temperamental changes.

In some cases, a dietary supplement comprised of a blend of vitamins, minerals, and herbs can help address nutritional deficiencies or even hormonal imbalances to help produce a calmer, more agreeable horse. There are currently a plethora of different calming supplements available. While some are very simple with only a single active ingredient, others are fairly complex and contain a variety of minerals, vitamins, and herbs to help combat anxiety and inattentiveness in horses. The following nutrients and herbs are ingredients found in popular supplements intended for over reactive horses. Each active ingredient will be discussed to explain what it is, how it is effective for calming horses, and the scientific thought behind it. With this information, a horse owner will be better equipped to make informed nutritional decisions on how to manage one’s hot horse.


Chamomile is a small white flower of the Asteraceae family that closely resembles a daisy in appearance. While there are many flowers that go by the name of chamomile, primarily only the German chamomile and the English chamomile are used for medicinal and supplemental purposes. Chamomile has long been used to help treat insomnia and anxiety in humans, particularly when dried, chopped, and used as a tea.

Chamomile naturally contains relatively large amounts of a plant nutrient called apigenin. Apigenin is the component of this herb that makes it a natural treatment for anxiety as well as providing a slight sedative effect. Given these effects, this herb would be best given to the anxious horse that needs a bit of the edge taken off, such as when trailering or staying at a new facility overnight. In addition, chamomile also has the benefits of being anti-inflammatory and anti-diarrheal.


A sugar-like carbohydrate, inositol is one of the lesser known B vitamins and also referred to as vitamin B8. Inositol is critical for messages sent between different cells, particularly those found in the brain and spinal tissues. The use of inositol oral supplementation has been proven highly effective in treating mental disorders in humans such as anxiety, obsessive compulsive disorder, and depression without any known side effects. While not found frequently in equine calming supplements, this is certainly a nutraceutical that is gaining traction.


Magnesium is a trace mineral necessary for muscle function, protein synthesis, and brain development and also one of the most common active ingredients found in calming supplements. This grey-green mineral comes in a variety of forms which vary greatly in how bioavailable they are to the horse. For example, inorganic magnesium oxide is relatively unavailable to the horse when compared to an organic form of magnesium like magnesium citrate. In addition, chelated or proteinated magnesium, which is magnesium bound to a protein, is even more bioavailable than organic forms of magnesium. What this means is that one must feed more inorganic magnesium to get the same level of absorption as organic forms of magnesium or chelated magnesium.

This trace mineral is believed to work as a calming agent in two different ways: 1) by increasing the body’s sensitivity to serotonin and 2) by acting as a natural GABA agonist. Serotonin is a neurotransmitter very important for a horse feeling contentment with their situation and more described below under tryptophan. One may be familiar with the term “GABA” as having something to do with the supplements that were banned by the USEF in early 2012. GABA, or gamma-aminobutyric acid, is a naturally-occurring neurotransmitter that is associated with calming and sedative-like effects. Despite the prohibition of all GABA-containing supplements, one does not have to worry about using magnesium as an oral supplement in horses. In this case, magnesium works by attaching to the GABA receptor sites to help regulate muscle and brain activity. Magnesium is what the body uses to naturally stimulate the production of GABA without the possible risks and side effects of GABA supplementation. When a horse is deficient in magnesium, a horse may be more irritable, hypersensitive, and anxious and may even exhibit slight muscle tremors or cramping. Through oral supplementation, one can address these issues with minimal risks since the horse is able to effectively mediate the amount of magnesium it uptakes. The most common side effect of magnesium over-supplementation is diarrhea, which is easily amended by reducing the overall amount of magnesium in the diet.


An amino acid touted for a variety of health benefits, from weight loss to high antioxidant activity to helping alleviate muscle soreness, taurine is an impressive supplement from numerous standpoints. From a calming perspective, taurine seems to help manage and alleviate anxiety, particularly in scenarios when the source of stress is external and unavoidable. This would be in cases when a horse is in an unfamiliar situation, such as a new show venue or trail. More interestingly, taurine supplementation has also been shown in studies on mice to help the mouse focus more on the task at hand despite the presence of distractions. This is an important attribute to note when a rider may require the horse to be mentally present in a performance-based challenge, such as during competition. Taurine’s ability to improve concentration is why it is a common ingredient in energy drinks as well.


Thiamine, or vitamin B1, is a water-soluble vitamin first noted for its cornerstone role in proper neural function. While some organisms such as bacteria and plants can synthesize thiamine, animals must obtain thiamine from their diet. The most commonly known disease associated with thiamine-deficiency is beriberi, which was primarily described in Asian countries during the late 1800’s and early 1900’s . Beriberi can cause a variety of symptoms including edema, muscle weakness, poor cardiovascular function, and weight loss. In addition, beriberi can cause severe neural symptoms, including poor muscle coordination, unexplained pain, and mental insufficiencies. Incredibly, all these symptoms are easily treated with administration of thiamine.

From a calming perspective, thiamine is important for the synthesis of GABA, which was briefly discussed earlier. When a horse is able to produce a sufficient amount of GABA in his system, he is more able to cope with the stresses he encounters, such as traveling, training, and changing herd dynamics.


Tryptophan, also seen as L-tryptophan on labels, is an essential amino acid. This means that it is one of many protein building blocks that a horse must obtain from his diet since the horse is unable to produce this amino acid otherwise. Not all amino acids are essential since some amino acids can be easily and efficiently produced by the horse. If a horse is deficient in an essential amino acid, then a host of issues can occur, such as poor muscle development, diarrhea, distended abdomen, and poor cognitive function.

The primary role of tryptophan in the body is as a precursor to the neurotransmitter serotonin. Serotonin is a neurotransmitter produced by the lining of the gastrointestinal tract and helps digestive movements and clotting of the blood in the case of injury. Serotonin also helps contribute to an animal’s sense of satiation and, thereby, directly impacts behavior. If an animal is satiated by its resource availability, it has been shown that he will be more agreeable and less quarrelsome. Adequate tryptophan levels and, subsequently, serotonin levels help the animal determine that he does not have to “fight” as much for resources, resulting in a more amicable horse. When humans eating diets low in tryptophan were examined, the deficiency of tryptophan also correlated with lower serotonin levels and more aggressive and depressive behaviors.

Tryptophan supplementation is best used in cases where the horse is overly exuberant and generally disagreeable. This essential amino acid is found in a multitude of different food items, such as barley, mushrooms, some seaweeds, and walnuts. Tryptophan is also found in high levels in stinging nettle, which is another herb that is found in a variety of equine calming supplements. In addition, stinging nettle can also help control inflammation, which is an important attribute for horses that are in rigorous work.

While challenging, hot horses are often one of the most rewarding types of horses to work with. Through diligent and proper management, training, and nutritional support, one is often able to transform a very nervous and incredibly athletic into a true competitor in the show ring or at work. By having a more thorough understanding of why certain ingredients are incorporated into different supplements and feeds, a thoughtful horse owner will have the knowledge to select the best calming supplements and overall nutritional plan to get the best out of their equine partner.


About Suzie Middlebrook, BSc | Cavalor Nutrition Specialist

Suzie Middlebrook is a budding equine nutritionist and lifelong equestrian. She graduated from California Polytechnic State University in San Luis Obispo, CA with her bachelor’s degree in animal science where she focused on equine and wildlife nutrition. While there, Suzie was instrumental in a number of feeding trials and experiments that looked at the fiber and mineral digestion in a number of different herbivorous species, including the red panda, the leopard tortoise, and the horse. Her personal project looked into developing an accurate and practical digestion model for the endangered red panda which she presented as an undergraduate at the Association of Zoos and Aquariums/Nutrition Advisory Group conference on Zoo and Wildlife Nutrition in 2011. Suzie loves talking and teaching about the peculiar nuances of equine nutrition and is able to do so as the Nutritional Specialist for Cavalor North America. When not “nerding out” on nutrition, Suzie enjoys competing her two horses in dressage and eventing, trail running, and playing with her boxer dog.


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