Magnesium And Thiamine Are No. 1 Nutrients For Calming Your Horse

If you’re looking for a quick-fix tranquilizer alternative that will instantly transform your horse into an automaton, this article isn’t for you.

Anyone with a horse that is too strong, too energetic, too eager, too forward for the job they want done, or for their level of riding expertise, needs a new horse, a trainer or both. You and the horse will be better off for it. Time, patience and retraining should also be used in an effort to solve behavior problems before hoping for a fix from a supplement.

Sorting Through

Before even considering a supplement, it can be helpful to define the problem you’re having:

• Horse was previously fine but develops behavior issues under saddle.

This could be a sign that the horse is hurting. Before doing anything else, make a list of things that trigger the behavior, such as being asked to jump, assume a canter lead, going up or down hills. These can be important clues to where the horse might be hurting. A horse like this may also simply be ”sour,” bored with its routine.

A stallbound horse might need a calmative. L-tryptophan is believed to be good for aggressive-type behaviors, but you may want to start using it two to three days before you think you’ll need it. Some horses respond well to thiamine supplementation. We had success with ExStress in our test horses.

• Horse was recently purchased and was fine with the old owner and fine when you tried her out, but at your barn is showing behavior issues.

We hope you had your vet draw blood to hold for drug testing as part of your prepurchase exam. Both short- and long-term tranquilizers (30 days or longer from a single treatment) can be used to make horses behave well for prospective buyers.

If you’re sure that’s not the problem, the horse may be testing you to see what she can get away with (try her with a more experienced handler and rider to see what happens), or she may simply be having trouble adjusting to her new environment and routine. Things like the loss of old buddies and changes in the level of turnout can lead to behavior issues. Different causes call for a different management and training approaches.

• Isolated resistances and phobias.

This would include things like resistance to being bridled/haltered, or an inordinate fear of clippers. Depending on the problem, the first step is to rule out a physical cause (like sore ears), but for the most part these are training issues and should be addressed as such, not with drugs or supplements. (See sidebar on densensitization.)

• Behaviors that may involve eyesight.

These include reluctance to enter a trailer, hesitation when moving from dark to well-lit areas, spooking, shying and being startled easily when approached from behind or only on one side. A thorough eye check, including the interior of the eye and the field of vision, should be done by a veterinarian or veterinary eye specialist.


Some horses may have perfectly normal eyes but unusually large corpora nigra, small ”balls” of pigmented iris that sit along the upper edge of the pupil. These are believed to normally act as visors against bright light but when large can actually block vision when the horse goes into bright light and the pupil constricts down.

• Nervousness or personality.

Much time, effort and money can be wasted if you are trying to change the horse’s basic personality. If we define ”nervousness” as an abnormal reaction, that’s one thing, but horses, like people, have different personalities and different likes and dislikes. Some horses are just naturally ”up,” eager, energetic, full of life and looking for action. This is different from nervousness, which includes signs of anxiety/fear, even physical symptoms such as sweating, trembling and diarrhea. It’s important to know the difference. If you try to change a horse that is just simply full of life into a disciplined show horse or bomb-proof trail horse, you’ll both be miserable.

True Supplement


Horses that are overly sensitive to touch or sounds, are genuinely fearful, nervous or anxious in predictable situations, where physical and training issues have definitely been ruled out — and you’re sure it’s not just a matter of the horse being naturally high-spirited — may be helped by the correct supplement. Another scenario for supplement use is horses on forced stall rest. Once you have determined a calming supplement may be useful, the next step is actually picking one.



In our ”Ingredients And Typical Effects” chart on page 6, we’ve listed the ingredients you’re likely to find in calming products. Unfortunately, little solid equine-specific information is available, so we’re forced to give you common human conditions.

In our own field trials and experience with horses and calming supplements, we’ve found the best results with thiamine, magnesium or combinations of the two when dealing with horses that are excessively nervous, easily startled and over-reactive. Horses that became pushy or aggressive when worked up also responded but not completely.

Overall, we’ve found the best responses were to magnesium in the range of 3 to 10 grams/day. The level of magnesium naturally present in most horses’ diets is considerably below the 1.5:1 to 2:1 ratio of calcium:magnesium recommended by some equine nutritionists.

If the horse isn’t receiving grain or doesn’t accept powders well, we found Foxden’s Quiessence pellets effective and palatable.

Vitamin B can sometimes enhance the response to magnesium. Horses are calmer but alert and full coordinated, not at all ”drugged.”

Thiamine has a long history of use as a calming supplement for horses, either orally or intravenously by a vet in combination with calcium. It doesn’t work 100% of the time, but when it does the results are very good with nervous and anxious horses. Dosage is 500 to 1000 mg/day.

Of the available herbal supplements, valerian produces the most obvious effects. With valerian-only, it takes about a week to see a difference, while with valerian-combination products, some calming was noted in a few days, more noticeable after 10 days to three weeks.

While the horses were calmer, or even ”dopey” in their stalls, the effects didn’t necessarily hold when the horse was stimulated. Horses that were hard to handle in the paddock, or spooky on rides, seemed to often snap out of the effects of valerian entirely under those conditions, but it’s a good choice for a horse on stall confinement.


Bottom Line

Before reaching for a calming supplement, take a detailed look at your problem to see if management changes or training aren’t better solutions. Make sure there’s no physical cause for the horse’s behavior, that you’re not actually over-mounted, that the horse enjoys the type of work you want from him and that you’re not mistaking a naturally high energy level and zest for life for a behavior problem. You can’t change personality.

If it truly is a situation where a supplement might help, first try adding magnesium oxide or thiamine alone to the horse’s diet. If this doesn’t work, we’d consider a commercial product that combines these ingredients. The nutritional approaches gave more consistent and reliable results with our test horses.

Of the products we’ve used, Seroquine, At Ease and ExStress produced excellent, solid results in our field-trial horses. Seroquine gets the nod for potency and price.

If your nervous horse also gets aggressive, we suggest you try either L-tryptophan alone, as is found in B-Kalm paste (which may work at even a half dose), or in combination with magnesium and B vitamins, a combo we like in At Ease.

Effects with the herbal-based products were milder and less reliable in our test horses, but with valerian producing the most obvious effects when dosing was high enough. Equilite’s Equine Relax Blend, the valerian-based formula, worked the best. Its combination of valerian with milder but more-rapid-acting herbs produced results quickly with peak effect in about two weeks.

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