Calming the Anxious Horse: 4 Nutritional Ingredients to Consider 

By Juliet M. Getty, Ph.D. 

Horses can become anxious, tense, or overly reactive for many reasons. Trailering, changes in routine, unfamiliar surroundings, separation from herd mates, veterinary or farrier visits, and even everyday training can challenge a horse’s ability to remain calm and focused. Before reaching for a calming supplement, it is important to consider the horse’s overall diet, environment, turnout, comfort, and management. But when those fundamentals are in place and a horse still needs additional support, certain nutritional ingredients may help take the edge off without compromising alertness or responsiveness. 

Choosing a calming supplement can be confusing 

The number of calming supplements available can be overwhelming. Formulas often contain several ingredients, sometimes in combinations that make it difficult to know what your horse actually needs. 

Rather than simply choosing a product with a long list of ingredients, I prefer to consider specific nutrients and nutraceuticals individually. Four, in particular, are worth considering. They can be used alone or, when appropriate, in combination. Understanding what each one does can help you choose the best approach for your horse’s individual needs. 

Start with magnesium 

Magnesium is often the first nutrient I consider for a horse who is unusually tense, nervous, overreactive. It plays an important role in normal nerve transmission and muscle function, and an inadequate magnesium intake can contribute to nervousness and increased reactivity. 

Before adding magnesium, however, consider the entire diet. Magnesium does not work in isolation, and its intake should be evaluated in relation to calcium. I generally aim for a calcium-to-magnesium ratio of approximately 2:1, although a ratio approaching 1:1 can also be appropriate. Magnesium intake should not exceed calcium intake. 

If additional magnesium is warranted, magnesium oxide is a practical and well-absorbed supplemental source. Organic forms, including magnesium citrate, malate, and proteinate, can also be used. 

For a horse whose behavior is related to inadequate magnesium intake, improvement may become apparent quickly. The horse will become less reactive, more comfortable, and better able to focus. If adequate magnesium supplementation produces no noticeable change, however, adding increasingly larger amounts is unlikely to be the answer. It is time to consider other possible nutritional, management, or physical causes of the horse’s behavior. 

B vitamins 

The eight B vitamins work together in many metabolic processes, including those that support normal nervous system function. Unlike people, horses generally do not require supplemental B vitamins because the microorganisms living in the hindgut produce them as part of their normal fermentation activity. 

There are times, however, when I consider adding a B-complex supplement. Stress, illness, antibiotic use, digestive disturbances, and diets high in starch can disrupt the normal hindgut environment. When microbial health is compromised, B-vitamin production may also be affected. Supporting the hindgut with an appropriate prebiotic and probiotic can help promote a healthy microbial population. 

Thiamin (vitamin B1) is of particular interest for the nervous or overly reactive horse. It is essential for normal carbohydrate metabolism and nervous system function, and inadequate thiamin can affect both behavior and energy metabolism. For this reason, thiamin is commonly included in calming formulations, often at levels considerably higher than the horse’s basic nutritional requirement. 

As with magnesium, however, more is not necessarily better. If a horse remains anxious or reactive despite an adequately balanced diet, it is important to look beyond individual nutrients and consider pain, digestive discomfort, insufficient forage, limited turnout, social stress, training, and other factors that may be contributing to the behavior. 

Ashwagandha 

Ashwagandha (Withania somnifera) is an herb with a long history of use in Ayurvedic medicine. It is classified as an adaptogen, a term used for substances that may help the body cope with physical and psychological stress and maintain a more balanced response to stressful situations. 

For the anxious or chronically stressed horse, ashwagandha is particularly interesting because of its potential influence on the stress response. Rather than acting as a sedative, it may help moderate the physiological effects of stress, including excessive activation of the hypothalamic-pituitary-adrenal (HPA) axis and the resulting cortisol response. 

This can be especially useful for horses dealing with ongoing stressors such as travel, changes in environment or routine, separation from companions, confinement, training demands, or competition. Chronic stress can affect far more than behavior; it can also influence appetite, digestive health, immune function, and overall well-being. 

Ashwagandha also has antioxidant and anti-inflammatory properties that may provide additional support for horses experiencing physical as well as emotional stress. For a full-sized horse, I generally use 1,000 to 1,500 mg per day. 

L-Theanine 

Not to be confused with the essential amino acid L-threonine, L-theanine is an amino acid derivative found naturally in tea leaves, particularly green tea. It has attracted considerable interest for its potential to promote a calm, relaxed state without causing sedation. 

L-theanine appears to influence several neurotransmitter systems involved in the stress response, including glutamate, GABA, serotonin, and dopamine. Rather than simply making an animal sleepy, its appeal is its potential to reduce excessive nervousness while allowing the horse to remain alert and responsive. 

This makes L-theanine an interesting option for horses that become tense or anxious during trailering, changes in surroundings, separation from companions, veterinary or farrier visits, training, or other stressful situations. It is increasingly included in equine calming formulations and may be particularly useful when the goal is to take the edge off without diminishing the horse’s awareness or ability to perform. 

As with other calming ingredients, however, L-theanine should not be viewed as a substitute for identifying the source of a horse’s anxiety. Pain, digestive discomfort, inadequate forage, social isolation, insufficient turnout, and inappropriate training or management should always be considered when nervous behavior persists. 

Most products combine several ingredients 

L-tryptophan is a common ingredient in calming supplements. This essential amino acid is a precursor to serotonin, a neurotransmitter involved in mood and behavior. For tryptophan to influence serotonin production in the brain, however, it must first cross the blood-brain barrier, where it competes with other amino acids for transport. 

For this reason, tryptophan may be more effective when given separately from a protein-containing meal rather than mixed directly into the horse’s feed. Paste formulations given between meals are one way to accomplish this. Although tryptophan is widely used in equine calming products, its calming effects in horses have not been consistently demonstrated, so I do not consider it as predictable as some other nutritional approaches. 

Herbs are also commonly included in calming formulas. These may include ashwagandha, rhodiola, magnolia, chamomile, raspberry leaf, valerian, and passionflower, among others. Each has different properties, and simply combining many calming ingredients does not necessarily make a product more effective. 

When evaluating a combination product, look beyond the ingredient list. Pay attention to the actual amount of each active ingredient and consider whether those amounts are likely to be meaningful. A long list of appealing ingredients can look impressive on a label while providing very little of any one of them. 

Above all, choose ingredients according to the individual horse. A horse whose nervousness is related to inadequate magnesium intake has a very different nutritional need from one responding to pain, digestive discomfort, environmental stress, or an inherently reactive temperament. 

Bottom line 

A horse’s behavior reflects many influences, including nutrition, physical comfort, past experiences, management, and his current environment. When nutrition is contributing to nervousness or reactivity, correcting an imbalance or deficiency — magnesium being one possibility — may make a noticeable difference. 

But no calming ingredient can compensate for pain, digestive discomfort, inadequate forage, insufficient turnout, social stress, or an environment that continually makes a horse anxious. Identifying and reducing those stressors may be the most effective calming strategy of all. 

When additional support is appropriate, there is no single calming ingredient that works for every horse. Some trial and error may be necessary, but choosing ingredients thoughtfully—and giving them in meaningful amounts—can help you find the approach that best suits the individual horse.