Adding Fuel to the Fire: How Diet Affects Horse Behavior

Find out how you can influence your horse’s behavior through feed management and ingredients.
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Adding Fuel to the Fire: How Diet Affects Horse Behavior
How and what you feed your horse might help calm him and combat behavioral problems. | Photo: iStock

What and how you’re feeding your horse could be causing undesirable behavior

Do you struggle with a horse that’s “feeling his oats”? You’re not alone. Equine nutritionist and Rutgers University equine extension specialist Carey Williams, PhD, says the question she most frequently hears involves a horse that’s hyper-reactive or hyperexcitable. “Is there anything I can do with his feed to calm him down?” they typically ask.

As it turns out, there’s a lot you can do with your horse’s feed to calm him, combat behavioral problems and stereotypies, and more. Much of it involves what you feed; some involves how you feed (management); and some involves what you do in conjunction with feeding (socialization, medical management, exercise).

Many factors contribute to your horse’s behavior: his instinct, genetics, environment, health, and comfort are chief among them. So what’s the basis for your particular horse’s problem? “You really need to know the horse’s natural behavior first to find out if anything else (besides diet changes) will work,” says Williams.

Determining the root cause of any problem can take trial and error, so be patient. Find a baseline first, then formulate a plan. Read on to learn more about how you can influence your horse’s behavior through feed management and ingredients.

Imitate Nature

In the wild horses graze 16-plus hours each day, choosing from a variety of forages and socializing and exercising with companions along the way. When Mother Nature provides sufficient moisture for a plentiful food supply, it’s a life of autonomy and low stress, except for the occasional threat from predators or for herd dominance.

Horses grazing in their natural environment might encounter some cereal grains as they roam, but for the most part their diet is one of grasses—grasses they choose.

How does that picture of nature compare to your horse’s diet and feeding routine? If your horse performs anything more than light work, his feed must deliver more energy than pure pasture might provide. And without realizing it, when we feed the low-forage, high-grain diet that’s common for performance horses today, we deprive them of many of the beneficial social and physiological aspects of eating. We often isolate them from other horses and feed a single source of hay, which they consume in under an hour. They don’t chew as often as they would if they were grazing. They’re confined to a stall or paddock, meaning we limit their natural exercise, too. How can we compensate for the changes we’ve made in our horses’ lifestyles through domestication?

The first thing we can do is imitate nature’s feeds and feeding model as much as possible. Carissa Wickens, PhD, equine behaviorist and equine extension specialist at the University of Florida, in Gainesville, recently visited a large Warmblood training facility in Denmark, where staff offered different types of forages in each meal.

“There were some types of legume hay and some types of grass hay,” she says. “This allows horses to visit each of the flakes, even if they had a favorite forage. So sometimes—especially if a horse has to be in a stall for a longer period of time or if you don’t have a lot of acreage to rotate pastures—enriching a horse’s environment by strategically placing some different types of forage around the paddock can get them to spend more time foraging, which can encourage good behavior.”

The performance horse requires energy for muscle contraction, so he needs some starch and sugar (in the form of grain-based concentrates and/or another supplemental feed) but should still be getting at least 1-1.5% of his body weight per day in forage (so, at least 10-15 pounds for a 1,000-pound horse).

But for the average horse, says Williams, the general rule of thumb is to offer 2-2.5% of the animal’s body weight in total feedstuffs per day. So, an all-forage diet and access to salt (block form or loose) can typically meet the nutrient requirements of a horse at maintenance or in light work.

“The second-best option is some sort of (processed) forage or hay cubes,” says Williams. “There are many on the market: timothy hay, grass hay, mixed with alfalfa, or straight alfalfa—anything along those lines is the next best thing to long-stem hay. Horses will consume pellets as fast as they consume their grain, but the cubes take a while to chew, so they also cut down on boredom, which cuts down on negative behaviors.

“Fiber ferments in the large intestine, so horses get that energy very slowly; that’s why forage and fiber are good for the maintenance horse that’s not doing a lot,” she continues. “They don’t need a lot of energy quickly, they just need slow-release energy throughout the day to maintain their body. But the exercising horse needs the stored muscle and liver glycogen that’s used when they’re exercising. Carbohydrates (mainly from grain) are digested and absorbed in the small intestine, where you get the big release of glucose and insulin.”

Devices such as slow-feed haynets and hay feeders that extend the forage meal seem to help horses mimic their natural eating behavior, too, says Wickens. Toys can also help alleviate boredom, as can time spent near other horses and/or in the company of barnyard pets such as goats and donkeys.

In addition to providing as natural a feeding experience as possible, increasing your horse’s exercise can take the edge off his fractious behavior.

Horse pinning ears
Some horses' negative behavior is attributable to discomfort associated with gastric ulcers--which diet changes can help resolve. | Photo: Thinkstock

Rule Out Pain

“Some horses begin to behave badly because they’re getting gastric ulcers or at least have an environment set up in the stomach that’s not very comfortable,” says Wickens.

If your veterinarian determines your horse has gastric ulcers, remember that in addition to using products specifically formulated for treating ulcers, managing a horse’s feeding patterns can help assuage pain: Chewing produces saliva, which lubricates food and buffers the stomach’s acidic environment. So, smaller, more-frequent high-forage meals result in slower food passage through your horse’s digestive system. This means less possibility of feed leakage into the hindgut and, consequently, less chance of heightened lactic acid levels that can cause colitis, diarrhea, gas, and even colic. Alfalfa is a good forage choice for horses with gastric ulcers; its high calcium content helps buffer stomach acid.

Another possible comfort issue is thermoregulation. “We have quite a few horses down here (in Florida) that are anhidrotic—they don’t sweat appropriately—so when temperatures get hot and it gets humid, they start to feel pretty miserable,” says Wickens. These animals sometimes display their discomfort with agitated behavior.

Evaluate Diet

Once you’ve explored the possible non-nutritional contributors to your horse’s behavior issues, you can experiment with nutrition as another means of behavior control. Feed, whether forage, grain concentrates, or other supplemental products, contains three main nutrients: protein, carbohydrates, and fats, plus vitamins and minerals. Here’s how each contributes (or doesn’t) to a horse’s “hotness,” and in which products you might find them.


The notion that a high-protein diet causes behavioral issues is incorrect. Protein, says Williams, is not related to energy at all. “(The excess energy) is more related to the calories of the feed source, not the protein of the feed source,” she says. “The majority of a horse’s energy comes from glycogen and also from fat.”

That said, proteins are made up of 20 amino acid “building blocks.” One amino acid of interest, tryptophan, is a main ingredient in many of the calming aids on the market. Because tryptophan is a precursor of serotonin, a neurotransmitter (it transfers signals between nerve cells) that modulates mood and activity levels, one might think that increased tryptophan would lead to increased serotonin levels. “But because of glucose and insulin releasing serotonin to the brain, just the opposite is true,” says Williams. ­“Tryptophan actually causes excitement in low doses in horses.

“There are a lot of products on the market,” she says, “but research hasn’t proved that tryptophan is effective.”

Carbohydrates and sugars and starches in grains can cause an immediate energy spike, followed by a slump several hours later. | Photo: Alexandra Beckstett/The Horse


Carbs comprise the so-called “hot feeds”: soluble carbohydrates, sugars and starches in grains—especially corn—and molasses. “Carbohydrates could be one of the main culprits if a horse is hyperexcitable,” says Williams. “I relate it to the kid who eats the entire bucket of Halloween candy, then runs around the house for an hour, and then about an hour and a half later they crash. That same thing happens to our horses’ systems. They have a spike in glucose and insulin about 60-90 minutes after they eat a high-sugar, high-starch meal, then a slump roughly four hours afterward when they crash.

“You’re going to get a higher glucose and insulin response when the sugars and starches are higher,” she continues. “Corn is usually the culprit because it’s the highest sugar- and starch-content grain out there—much higher than oats, which are actually one of the lowest, and barley falls toward the low end in the middle.”

Molasses, however, might be an unwarranted member of this “hot” group. “Horse owners shy away from molasses, but molasses isn’t really the issue,” says Wickens. “Molasses is added as a binding agent and isn’t as high in sugar as many people think. The problem is more the amount of grain you’re feeding, as well as the grains’ sugar content.”

Wickens focuses her research on physiological responses to feeding as they relate to stereotypic behaviors. “We do see a spike in cribbing frequency related to hot feeds,” she says. “These horses will start crib-biting more after they receive a concentrate meal. Highly palatable feeds seem to stimulate bouts of cribbing behavior, but the relationship between diet characteristics, feeding management practices, and stereotypic behaviors is still not completely understood. Changes in brain chemistry and in the gastrointestinal tract in response to feeding appear to play an important role in cribbing behavior, but the root cause of the behavior is likely a combination of factors.”


Fats: Not Just an Equine Diet Fad
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Fat molecules, which get absorbed in the small intestine, are about three times as energy-dense as carbohydrate molecules, so they provide a lot of energy without the sugar high that carbs’ quick absorption produces. “You might even call fat a cool source of energy rather than a hot source,” says Williams. “You don’t get that burst of energy from catalyzing fat.

“Think about an endurance horse,” she adds. “It’s going for 100 miles at a time but it’s not using a lot of glycogen and high-carbohydrate sources that are going to be gone fairly quickly. It’s using a lot of fat.”

Researchers have shown that feeding fat to horses actually reduces hyperexcitability and reactivity to stimuli compared to feeding sugary, starchy meals.

Vitamins, Minerals, and Supplements

Many of the calming aids on the market contain B-vitamins, particularly thiamine. “There’s not a lot of research out there to back calming claims, but the theory is that horses with thiamine deficiencies can have anxiety behaviors related to brain function, sometimes including convulsions, so the more thiamine, the less nervousness and anxiety,” says Williams, “The good thing is, being a B-vitamin, it’s water-soluble; the horse will eliminate any excess in his urine so it can’t be toxic.”

While some herbals such as valerian have proven sedative properties, many are banned substances in competition. | Photo: iStock

Another mineral purported to have calming properties is magnesium. The rationale behind its use resembles that of thiamine: deficiency causes nervousness, tremors, and excitability, so more magnesium will counteract that. “Research and anecdotal evidence have shown that to work only about 20% of the time,” Williams says. “If you’re ­feeding ­several supplements that might also have magnesium in them, remember that it does have a toxicity level that’s fairly easy to reach, and it’s not water-soluble like thiamine is.”

Then you have the herbals many claim have therapeutic properties. One of these is valerian, which Williams says researchers have proven to have sedative properties, although not specifically in horses. “It decreases central nervous system activity,” she says. “But use care if you’ll be competing, as it’s on the banned-­substances list of show circuits such as Fédération Equestre Internationale and the American Quarter Horse ­Association.”

And for all supplements, beware of balance and toxicity issues that can arise; nutritionists like Williams (call your state’s extension service horse specialist) can perform a nutritional consult to evaluate your horse’s diet for any red flags.

Take-Home Message

“Horses that have a more sensitive or reactive temperament could be at greater risk of developing behavioral problems, particularly when they’re fed excess calories and limited forage,” says Wickens, noting that more research into this is needed.

What it all boils down to is that the more you can pattern your feed and feeding routine after nature, the better. Once you’ve established a baseline for your “hot” horse’s normal behavior, you can implement one or more of a host of fixes, including nutrition, to help.


Written by:

Diane Rice earned her bachelor’s degree in agricultural journalism from the University of Wisconsin, then married her education with her lifelong passion for horses by working in editorial positions at Appaloosa Journal for 12 years. She has also served on the American Horse Publications’ board of directors. She now freelances in writing, editing, and proofreading. She lives in Middleton, Idaho, and spends her spare time gardening, reading, serving in her church, and spending time with her daughters, their families, and a myriad of her own and other people’s pets.

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