Riding and working with horses poses some inherent risk of danger, but the risk is greater when working with an reactive or unpredictable horse.

For this reason, horse owners often look to calming supplements to help make their horse more manageable and easier to train.

Calming remedies are also used during stressful situations such as trailering, showing, farrier work, and veterinary visits.

Despite their popularity, calming supplements may be one of the least studied supplement categories in horses. Behaviour can be hard to quantify which makes it a difficult topic for researchers to study.

Furthermore, the root cause of why your horse is “hot” can be hard to pinpoint. Calming remedies that work for one horse might not work on another horse in a different situation.

Supplements are often formulated based on ingredients with evidence for calming effects in other species, such as humans and mice. However, with limited research on calmative agents in horses, it is difficult to evaluate many of the claims made for equine products.

This results in confusion for horse owners. In a recent survey of Scottish horse owners, 32% reported that they did not know what ingredient in their supplement caused a calming effect and only 40% reported seeing positive results. [1]

In this article, we evaluate the mechanisms, bioavailability, safety and efficacy of some of the most popular ingredients used in calming supplements for horses available on the market today. We also rate the ingredients on the strength of the research evidence in horses.

Anxious Behaviour in Horses

Acute Stress Response

Anxious or problematic behaviours in horses are typically normal physiological responses to stressful or unfamiliar situations. However, these behaviours may be undesirable or dangerous for the rider or horse owner.

Some horses show anxious behaviour transiently during stressful situations such as trailering. These horses may be otherwise calm and only display anxious behaviours in novel circumstances.

Common examples of such behaviours include: [2]

  • Problems loading into the trailer
  • Reluctance to move forward
  • Refusing to jump fences

Gradual, gentle introduction to new situations is recommended to avoid reinforcing avoidance behaviours.

Trailering and transportation also remove horses from their social group which is naturally stressful for horses. Young horses should be introduced to stressors such as social isolation and trailering gradually with short, progressive exposure to the stressor.

Horses may also identify cues for upcoming stressors. For example, a horse may show reluctance to move forward out of the stall if they anticipate ill-fitting tack or poor riding skills. [2]

In research studies, trailering has been shown to increase levels of the stress hormone cortisol in the horse’s blood. This hormone increases heart rate, particularly at the beginning of transport.

The good news is that horses can become habituated to transport and other common stressors, showing lower levels of cortisol in subsequent trailering events. [3][4]

Taking steps to remove or reduce these types of stressors can go a long way to calming your horse.

The fight-or-flight hormones adrenaline (epinephrine) and noradrenaline (norepinephrine) are also increased during stress and illness. These hormones, as well as cortisol, were found to be elevated in horses with acute laminitis and those with acute abdominal syndrome. [5]

Stereotypic Behaviours

Some horses develop problematic repetitive, abnormal behaviours that are expressed in their day-to-day life. These are known as stereotypies and include cribbing, stall-walking, weaving and windsucking.

Stereotypic behaviours are commonly thought to be adaptive coping mechanisms that have a soothing effect on the horse. [2]

In addition to making it difficult to handle these horses, persistent anxiety can have other issues, such as:

  • Reduced feed intake
  • Weight loss
  • Poor performance
  • Increased risk of injury


If your horse is displaying stereotypic behaviours, consult with your veterinarian to identify any underlying issues or concerns that may arise due to the repetitive behaviour.

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How to Support Anxious Horses

If your horse is displaying unruly behaviour, the first step is to identify any underlying health or management issues that need to be addressed.

Start by evaluating the following possible causes of anxious behaviour:

  • Untreated pain
  • Lack of turnout
  • Lack of exercise
  • Pent-up energy
  • High carbohydrate feeds
  • Digestive distress
  • Inappropriate training programs

The most important strategies for supporting calm behaviour in your horse include the following:

  • Provide plenty of turnout that enables expression of foraging behaviours
  • Ensure your horse’s energy intake is not exceeding requirements by determining needs and weighing feed
  • Feed a predominantly forage-based diet with low or no concentrates such as grains or commercial feeds
  • If additional caloric energy is needed, use fats instead of carbohydrates
  • Ensure your horse’s diet is properly balanced
  • Provide enriching, stimulating activities to help prevent boredom


If your horse is still acting “hot” with a balanced diet, adequate foraging, and appropriate exercise, it may be time to consider adding a supplement.

For help with designing an appropriate feeding program that supports calm behaviour, submit your horse’s information online for a free diet analysis by our equine nutritionists.

Top 6 Calming Supplements for Horses

1) Magnesium

Magnesium is an essential macromineral for all animals. The majority of magnesium in the horse’s body is found in bone and muscle. [6] This electrolyte also participates in enzyme activation and muscle contraction. [7]

Magnesium is used in calming supplements to reduce excitability, anxiety, and reactivity. In human studies, it has been shown to influence nerve transmission and support an anxiolytic (anti-anxiety) effect.

In horses, magnesium deficiency can result in anxious behaviour and supplementation may be beneficial for overcoming low dietary intake of this mineral.

However, it is unclear whether supplementing with magnesium beyond the amount required to avoid deficiency can calm an excitable horse.

Proposed Mechanisms of Action:

  • Inhibition of calcium channel thereby causing vasodilation [8]
  • Modulation of the hypothalamus-pituitary-adrenal axis to decrease cortisol production

Bioavailability and Safety:

Magnesium is primarily found in forages including pasture and hay. Moderate-quality hay will generally supply more than adequate amounts of this mineral. [9]

However, magnesium deficiency can occur with clinical signs consisting of anxiety, poor coordination and muscle tremors. [7] Other signs of deficiency include excitability, irritability, muscle pain, and sensitivity to sound. [10]

Magnesium toxicity has not been studied in horses. A maximum dietary concentration of 0.8% has been set and excess magnesium is excreted in urine. [7]

Magnesium is primarily absorbed in the small intestine and less so in the large intestine. [9] Magnesium citrate, chloride, lactate, and aspartate are highly absorbable forms of this mineral. [7]

Magnesium oxide is most commonly used as a dietary supplement because it provides good oral bioavailability and a higher concentration of elemental magnesium compared to other sources while still being quite cost-effective. This makes it a good option if supplementation is warranted.


Intravenous magnesium sulphate (MgSO4) is effective when administered to horses prior to competition to reduce anxiousness. [11] Because of its potential to enhance competition performance, it is considered an FEI prohibited substance.

Horses that have received intravenous MgSO4 infusions exhibit a lower head height, which serves as an indicator of sedation. [11]

Although intravenous magnesium shows a calming effect, oral supplementation has not demonstrated consistent results. Horses supplemented with magnesium aspartate had a reduced reaction time to being startled in one study, but not in another study. [12][32]<