A hyperactive horse is commonly referred to as a “hot” horse. You may know the feeling of dealing with a hot horse all too well: it can feel like your horse is going to explode at any moment.

Hot horse behaviour is associated with changes in stress hormones. Cortisol is a stress hormones that has a cascading effect on the horse’s body. [1][2][3] Chronically elevated cortisol levels in horses are associated with ulcers, colic, and impaired immune function. [4][5][6]

Hyperactive behaviour can manifest as:

  • Overreacting to new stimuli
  • Nervousness and anxiety
  • Bucking
  • Bolting
  • Rearing while on the ground or under saddle

This unwelcome behaviour is dangerous to both horse and owner, creating fear and tension. In some cases, an owner might choose to sell their horse if the behaviour becomes too much for them to handle.

Luckily, there are strategies that can be implemented to help manage hot horses. The first step is to ensure your horse has a well-balanced diet with the right amounts of energy, vitamins, and minerals.

It is also important to manage your horse’s daily routine and exercise regimen. Enabling their natural species-appropriate behaviours and minimizing boredom and frustration can also have a calming effect on some horses.

You can submit your horse’s information online and our equine nutritionists can help identify changes to your horse’s nutritional management that can promote calm behaviour.

Why is my Horse Hot?

Wondering why your horse is displaying hyperactive behaviour? It may just be your horse’s personality: hot-blooded breeds such as Thoroughbreds and Arabs are known to be more reactive than others.

However, if your horse is uncharacteristically hypersensitive then a multitude of factors may come into play.

These factors can range from nutrition, training, inhibition of natural behaviours, and environmental pressures.

Mad About Horses
Join Dr. Chris Mortensen, PhD on an exciting adventure into the story of the horse and learn how we can make the world a better place for all equines.
Apple Podcasts Spotify Youtube
Mad Barn Equine Nutrition Consultants

1) Feeding excess energy

Your horse’s daily calorie requirement is specific to its age, weight, exercise level, and life stage. Caloric energy is required to maintain bodily processes and fuel your horse’s daily activities.

Forage and pasture should provide the majority of energy in your horse’s diet. Having too much of a good thing can lead to your horse’s diet exceeding its energy needs.

Horses can easily get too much energy when on high-sugar grasses in the Spring and Autumn. High-quality hays can also provide excess caloric energy and horses on high-grain diets often over-consume calories.

When energy intake exceeds requirements, the excess calories will be deposited as fat or expended through unwanted behaviour.

2) Feeding “Hot” Feeds

Some feeds are considered “hot” because they increase the likelihood of your horse displaying hyperactive behaviour.

Hot feeds contain ingredients that spike blood sugar levels. These are sometimes referred to as high-glycemic feeds because the sugars in these feeds are metabolized quickly and lead to a rapid increase in insulin secretion.

“Hot” feeds generally contain higher levels of sugar and starch, collectively referred to as non-structural carbohydrates (NSC).

NSC is a measure of the sugars found within plant cells. These sugars are readily digested and absorbed in the small intestine, resulting in a rapid increase in circulating sugar in the blood (serum blood glucose levels). [7]

Common hot feeds include grains such as wheat, corn, and barley, as well as commercial feeds, sweet feeds, molasses and other sugar sources.

Energy-dense feeds like plant oil or alfalfa are sometimes mistaken as hot feeds. While these feeds are energy-dense, they do not affect blood sugar to the same extent as high glycemic feeds like grain. [8]

Fat and fibre are metabolized slowly and do not spike your horse’s blood sugar levels. These cool energy sources can decrease stress and spooking compared to high starch and sugar feeds. [9]

3) Forage Composition

Forage selection can play a major role in causing your horse to become hot. The sugar and NSC composition varies for different sources of pasture and different hays.

Cool-season grasses such as timothy, brome, fescue and orchardgrass tend to have higher NSC levels. These grasses can also accumulate fructans – a type of sugar.

In contrast, warm-season grasses such as bermudagrass generally have lower NSC levels and accumulate more starch than sugars. [20]

Horses grazing on high NSC pasture and hay are at higher risk of metabolic concerns, laminitis, and reactive behaviour.

It is recommended to get a hay analysis to help you select the right forage for your horse.

Hay Analysis
Know exactly what nutrients your horse is getting in their diet with our comprehensive equine forage testing.
Order Now

Growing Conditions and NSC Levels

Sugar levels also vary depending on growth, management, and harvesting conditions. Stress conditions such as drought and over-grazing can cause sugars to accumulate in pasture. [10]

Cold climate grasses have evolved to produce more NSC when stressed by cold temperatures so they have a better chance at surviving winter.

During drought conditions, grasses will increase their NSC production to ensure they have ample energy for a quick growth spurt when the rain returns. [11]

Overgrazing also causes the grass plant to experience stress because its photosynthetic food production is limited by leaf removal. The grass responds by trying to store as much energy as possible to grow when grazing pressures ease. The result is higher NSC grass.

4) Vitamin and Mineral Deficiencies

Nutritional imbalances in your horse’s diet can also affect their behaviour. If certain vitamins and minerals are not supplied in adequate amounts or if the ratios of these nutrients are out of balance, hot behaviour may occur.

In our analysis of thousands of equine diets, most have deficiencies in one or more vitamins and minerals which could contribute to anxious behaviours. Feeding a well-balanced mineral and vitamin supplement can help to correct for common deficiencies.


Magnesium plays an important role in muscle contraction, metabolism, and electrolyte balance. [12] Magnesium is also important for neurological function and mood balance.

Deficiency in this mineral can result in nervousness in the horse. A magnesium-deficient horse may exhibit excitability, anxiety, irritability, muscle pain or tremors, and sensitivity to sound. [13][14]

Supplementing with magnesium may have a calming effect if your horse is deficient. However, supplementation is unlikely to have a calming effect if your horse already obtains adequate amounts of this mineral from the diet.

Excess magnesium is readily excreted in the urine and not stored in the body. For this reason, we recommend submitting your horse’s diet for analysis first so a nutritionist can review magnesium levels in your feed and forage.

B-Complex Vitamins

B-vitamins can also play a role in keeping your horse calm. Both Vitamin B1 (thiamin) and vitamin B2 (riboflavin) contribute to nervous system function and mood regulation.

Clinical thiamin or riboflavin deficiencies are very rare in horses because these B-vitamins can be manufactured by the bacteria in your horse’s gut. [15]

However, B-vitamin production in your horse’s gut can be compromised in young, old, ill or stressed horses. These horses might benefit from additional B-vitamins in the diet to help modulate their behaviour.


Tryptophan is an amino acid that is a precursor to the production of the “happiness” hormone, serotonin. Tryptophan is also famously associated with making humans feel sleepy after a Thanksgiving turkey dinner

Many equine calming supplements contain tryptophan as the primary active ingredient. However, deficiency in horses has not been observed and research into supplementation has not demonstrated efficacy for promoting a calming response in horses. [16][17]

5) Mycotoxin Contamination in the Feed

Most horse owners associate mouldy hay with respiratory problems, but the toxins from mould called mycotoxins can make some horses hypersensitive. [16]</