Taking the Edge Off: Calming Supplements for Horses

Learn which calming supplement ingredients work and things to consider before choosing or administering a product to your horse.

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Calming Supplements for Horses
Owners might reach for calming supplements to help horses retain focus under saddle or cope with stressful situations such as trailer loading or health care procedures. | Photo: Photos.com

Calming supplement ingredients that work and things to consider before choosing or administering a product

You’ve spent significant time training and preparing your horse for a clinic or competition, only to get there and have him behave poorly. He’s excitable and unfocused and spooks at things that never bothered him at home.

Does this scenario sound familiar? I had it happen with my Thoroughbred gelding Duke. We had a well-known trainer running a multiday clinic at the barn where I boarded. Even though I had been out of town for a week, I really wanted to ride. But when I walked Duke into the ring—an arena we trained in daily—he started acting “squirrelly.” We tried to work through it but ended up putting him back in his stall for the day. The next day we tried again, and he was great. Still a little “up” but listening and responding to my cues. For Duke, it just seemed he needed to be in the situation a second time to realize everything was okay.

In situations such as this, you might ask what you can do to keep your horse from being so nervous. One option many owners reach for is a calming supplement. These are not chemical tranquilizers but, rather, products designed to help horses retain focus.

Sue McDonnell, PhD, Cert. AAB, founding head of the Equine Behavior Program at the University of Pennsylvania School of Veterinary Medicine, in Kennett Square, says she typically gets multiple calls a week from veterinarians looking for calmative recommendations. The horses are most commonly “stallbound layup patients,” she says, but calming supplements might be useful “in a variety of scenarios, such as training or show situations, health care procedure difficulties or aversions, loading and trailering worries, anxious breeding stallions, separation stress, weaning stress, stereotypies, and more.”

Pinpointing Problems

Before reaching for a quick-fix calming supplement in one of these situations, however, start by evaluating your nervous horse and his environment. Because horses are “fight or flight” animals, they often fall back on these instincts when faced with stressful scenarios. They are essentially hard-wired to try to flee from new circumstances or conditions beyond their normal routines. When they can’t escape they often express their nervous energy in less-than-desirable ways.

As horse owners, we can try to find outlets for this energy. This could be as simple as allowing additional turnout time or longeing a horse before riding. In addition, exposing horses to a variety of situations can help desensitize them to and become more accepting of new circumstances. If you need help, consider working with an experienced trainer. These professionals can help horses overcome nervousness and give owners and riders training and management recommendations.

McDonnell says it’s also important to evaluate the horse’s health to make sure a medical reason isn’t behind his behavior, because conditions such as gastric ulcers can lead to behavior issues. Horses that are in pain due to injury might also exhibit negative behaviors.

Evaluating a horse’s diet before adding a calming supplement is also very important, because several dietary components can affect behavior. Imbalances and deficiencies in some nutrients can contribute to behavior disorders. In these cases a calming supplement that contains one of these nutrients might help. Work with an equine nutritionist to assess your horse’s diet and determine whether dietary excesses or deficiencies are causing behavior problems. What follows are some of the more common and effective natural calming additives on the market. The first three are designed to address certain deficiencies, while the latter four are simply helpful additives.


Magnesium is a prevalent nutrient in calming supplements. It’s often poorly absorbed from feedstuffs, so you might need to supplement it simply to meet a horse’s needs. Magnesium is important for proper muscle contraction and nervous signal transmission. Misfiring of nervous system components can cause horses to appear nervous, irritable, or especially sensitive to new situations. Have a qualified equine nutritionist evaluate your horse’s diet, then add magnesium if it’s needed. If the horse is truly deficient, you should see an attitude change within a few days of starting magnesium supplementation.


L-tryptophan is an essential amino acid, meaning it needs to be supplied in the horse’s diet—the horse’s body alone can’t produce it. L-tryptophan is involved in synthesizing serotonin, a central nervous system hormone and neurotransmitter that can create feelings of relaxation and contentment and is often considered an “anti-stress” hormone.¹

“A problem with suggesting L-­tryptophan is that it is usually in horse products in combination with one to several other ingredients for which there is little or no solid evidence for their safety and efficacy,” cautions McDonnell. “So the important message in my view for using L-tryptophan as an aid to calming is to find a product with L-tryptophan as the only active ingredient.”

B Vitamins

Several B vitamins work together to promote nervous system health. Most horses with healthy hindgut microbial populations produce more than adequate amounts of these nutrients. However, high-starch diets, stress, and antibiotic administration can reduce the microbial population and, therefore, decrease vitamin production. Adding prebiotics and probiotics or supplementing with individual B vitamins can help.

Thiamine (vitamin B1) is one of the B vitamins that plays a role in fat and carbohydrate metabolism. Horses deficient in B1 often appear stressed and nervous, and supplementing the diet with this vitamin might bring about positive behavior changes.


The milk peptide alpha-casozepine has shown promise as a calming supplement. Some of the amino acids within this protein are linked to the “calming effect” observed when young mammals nurse. Alpha-casozepine’s structure is similar to that of some anxiolytic benzodiazepines (sedatives found in anti-anxiety medications), and it seems to work like one, as well. It does not appear to cause any of the negative side effects (agitation, incoordination, and even recumbency) sometimes seen with benzodiazepines, however. This peptide has also been studied in other animal species, such as rats, cats, and dogs, and researchers saw positive results on stress and anxiety. In McDonnell’s lab research teams have conducted several alpha-casozepine studies and found that supplementation helps lower horses’ stress levels under normal management situations and might help horses retain newly learned tasks.²

Taking the Edge Off: Calming Supplements for Horses
Anecdotal evidence suggests the herb ashwagandha can reduce stress and tension by reducing the horse’s “fight-or-flight” cortisol response. | Photo: iStock


Ashwagandha (Withania somnifera) is an herb that’s been used in both humans and animals as a natural antidepressant.³ Anecdotal evidence suggests it can reduce stress and tension by reducing the fight-or-flight cortisol (the stress hormone) response. Some owners have reported a decrease in stereotypies such as cribbing and weaving after supplementing their horses’ diets with ashwagandha. The herb might also help reduce pain, such as from athletic injuries or arthritis. Scientists have not yet performed peer-reviewed studies, however, to confirm this.

Valerian Root

Valerian root is another common herb found in calming products. In humans it can soothe edginess, reduce anxiety, and work as a sleep aid. In horses it has also been used as an antispasmodic (for treating colic). However, some equine associations have banned this ingredient, so it might not be an option if you compete. In addition, valerian can enhance the effect of synthetic sedatives or tranquilizers, so avoid giving it to a horse that will need tranquilizer for procedures such as dental work or body-clipping.


Another common herbal remedy is chamomile, which is of the Asteraceae family. Apigenin, the plant nutrient that occurs in relatively large amounts in chamomile, is what brings about both the calming and sedative effects observed. Although there are several flowers in the family, the German and English varieties are the ones most commonly used for calming purposes. In humans chamomile is used to treat insomnia and anxiety. It has also worked as both an anti-­inflammatory and antidiarrheal—­potential added benefits for nervous horses. However, many equine organizations ban the use of sedatives, even natural ones such as chamomile.

Take-Home Message

Horse owners should completely evaluate what might be causing a horse’s undesired behavior before trying a calming supplement. First eliminate health conditions, training issues, and dietary imbalances as causes. If you do decide to try a calming supplement, make sure it’s one that’s backed by research showing it works, is safe, and is legal for use in your breed and/or discipline competitions.

McDonnell also recommends only using those supplements with ingredients that have shown positive results in blinded, peer-reviewed research.

“Putting trust in an unproven or ineffective treatment can increase safety risks both for people and horse,” she says. “And from a horse welfare standpoint, only known effective and safe treatments should be used.”

Also, first try any supplement at home on a normal day to evaluate how it works on your horse before using it in a stressful situation on the farm or away from home. Try only one product at a time to determine if it works and to ensure it produces no side effects.


1. Davis BP, Engle TE, Ranson JI, and Grandin T. 2017. Preliminary evaluation on the effectiveness of varying doses of supplemental tryptophan as a calmative in horses. Applied Animal Behaviour Science, 188:34-41.

2. McDonnell SM, Miller J, and Vaala W. 2013. Calming benefit of short-term alpha-casozepine supplementation during acclimation to domestic environment and basic ground training of adult semi-feral ponies. Journal of Equine Veterinary Science, 33(2):101-106.

3. Singh N, Bhalla M, De Jager P, and Gilca M. 2011. An overview on Ashwagandha: a rasayana (rejuvenator) of Ayurveda. African Journal of Traditional, Complementary and Alternative Medicines, 8(5 Suppl):208-213.


Written by:

Janice L. Holland, PhD, is an Associate Professor and Director of Equine Studies at Wilson College in Chambersburg, Pennsylvania. A graduate of both Penn State and Virginia Tech, her equine interests include nutrition and behavior, as well as amateur photography. When not involved in horse activities she enjoys spending time outdoors enjoying nature.

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