Decipher fact vs. fiction when it comes to the complicated world of feeding horses.

7 Equine Nutrition Myths Busted

While we don’t know exactly why some horses lick dirt, it’s probably not because their diets are lacking in certain nutrients. | Photo: iStock

Haven’t you heard that feeding a hot bran mash will help prevent colic in the winter?” Horse owners pass feed fallacies such as this down the barn aisle on a daily basis. Nutrition is one of the most difficult aspects of horse management to understand, so it’s no wonder that forage and other fodder falsehoods sprout and take root, becoming accepted as conventional wisdom. Without getting a master’s or doctorate degree in equine nutrition, how do you decipher fact vs. fiction? Here we’ll help you bust some common myths about feeding horses.

Myth 1: Horses have “nutritional wisdom” and will seek out nutrients to meet their needs

“I recently started noticing my horse licking the dirt out in the pasture. Could he be missing important nutrients in his diet?”

Dirt-eating, or geophagia, is a fairly common behavior in both feral and domesticated horses. Researchers observing this behavior in feral horses in 1979 believed they might be licking the soil to increase their salt intake. In a 2001 study in Australia, researchers evaluated soil from 13 sites where horses were eating dirt and found that the samples contained elevated levels of iron and copper compared to paired control samples, and even horses offered supplemental mineral mixes or feed were among the study group.

The truth is we don’t know exactly why horses lick dirt, but it does appear that they exhibit this behavior even when their diet adequately meets their nutrient needs.

One way to potentially curb geophagia is by offering free-choice good-quality forage at all times. Use small-hole haynets or other feeders to help extend mealtime, leaving less time for boredom (another theorized reason for geophagia) and potential dirt-tasting.

With regard to nutrients such as carbohydrates and protein, we know very little about horses’ ability to self-regulate intake based on nutritional needs, but the high prevalence of obesity among horses certainly seems to disprove this myth.

Myth 2: Feeding grain will cause a horse to colic

“A friend of mine read that feeding grain to horses will make them colic. Is this true?”

In its simplest form, colic is abdominal pain and can be caused by many factors. The horse’s gastrointestinal (GI) tract is long and complex with twists and turns, all of which are susceptible to distention, twisting, inflammation, or displacement. Yes, feed can be a cause of colic, but specific aspects of diet, feed characteristics, and management can all be partly to blame.

A horse’s risk for feed-related colic increases with:

  • Total grain intake exceeding 11 pounds per day;
  • Decreased or no pasture availability;
  • Increased consumption of poor-quality hay; and
  • Decreased water intake.

It is simply impossible to generalize all commercial grain products as potential causes of colic because they are intrinsically different. Yes, a large volume of any type of feed ingested at one time can cause colic, but other factors, such as sugar and starch, also contribute. Sugar and starch levels in grain products vary depending on the feed’s intended purpose. Racehorses, for example, rely on sugar and starch as their main source of energy and typically consume more than 11 pounds of grain per day, so they are at a higher risk for colicking. Compare that to a senior horse eating a high-fat and fiber feed at 6 pounds a day. His risk for having a feed-related colic episode is lower because of both the volume of feed per day and the ingredients.

The equine hindgut, which is another name for the large intestine, houses a unique biosystem of microorganisms whose main function is to break down fiber. The small intestine typically digests and absorbs sugar and starch, but in certain cases, such as after the consumption of large grain meals, these can spill over into the hindgut. Microbial breakdown of sugar and starch produce a more acidic environment (known as hindgut acidosis) and, in certain cases, colic.

Myth 3: Beet pulp must be soaked before feeding, or it will cause a horse to choke or rupture its stomach

“I have heard that feeding beet pulp without soaking it will cause a horse to choke.”

Beet Pulp

Feeding dry beet pulp will not cause your horse to choke–unless he bolts or doesn’t chew his feed properly. | Photo: Erica Larson, News Editor

Beet pulp will not cause choke simply on its own. Yes, a horse can experience choke, or esophageal obstruction, when eating beet pulp shreds or pellets, but this is generally a problem that starts with negative mealtime behaviors, such as bolting feed or improper chewing.

Also, there is zero evidence to show that beet pulp will cause your horse’s stomach to rupture. Yes, adding water to beet pulp does cause it to increase in size, but this does not affect what happens in the horse’s stomach. “Over the years, I have been unable to find documented cases of a horse’s stomach’s rupturing due to beet pulp,” says Burt Staniar, PhD, associate professor of equine science at Pennsylvania State University, in University Park. In fact, researchers at the University of Kentucky were able to feed up to 55% of the horse’s daily intake as unsoaked beet pulp without any adverse effects—much less stomach ruptures.

Myth 4: Too much protein makes my horse “hot.”

“When I feed my horse alfalfa or anything with a lot of protein, she gets spooky and is difficult to handle.”

This is by far the most common myth I encounter as an equine nutritionist. Think about this: A horse consuming a protein-deficient diet might exhibit somewhat dull or subdued behavior. If you then increase the protein level in the diet to the horse’s requirements or beyond, total feed intake also increases. Can the behavioral issues be related to total feed intake, or are they simply a result of going from a deficient diet to one that meets nutritional needs?

Chemically speaking, there isn’t much evidence to explain why protein affects a horse’s behavior. Carbohydrates, particularly sugar and starch, can affect behavior in some horses, but genetics and environment also play a role, making it difficult to pinpoint the exact cause. Researchers have determined that the digestion and absorption of sugar and starch might increase cortisol (the “stress hormone” from the adrenal gland) levels and cause behavioral changes—in some horses more than others. On the other hand, protein digestion and absorption does not affect cortisol levels, simply providing the horse with essential amino acids and contributing very little to energy production. In fact, some amino acids (such as tryptophan) produce a calming effect and are sold as supplements, although research has not supported their use in horses.

Myth 5: Corn is horrible for horses.

“I would never feed horses corn because it is bad for their health.”

Pre-Cecal Starch Digestability Chart

*Adapted from Meyer et al. 1993. USDA-APHIS

This statement is not true, but there are some caveats. Corn is a calorie-dense grain with an average starch concentration of around 70%. For the right class of horse, such as racehorses, endurance horses, or elite eventers, corn can supply vital energy for performance or for adding weight or condition.

Although corn doesn’t have a fibrous hull like whole oats do, its hard outer coating requires some form of processing to be fed safely and effectively. The graph illustrates the differences in pre-cecal (before reaching the cecum in the large intestine) starch digestion when horses consumed either whole, cracked, ground, or extruded (cooked with pressure and moist heat until it “puffs”) corn. You can see that by grinding or extruding corn, as much as three times more starch gets digested in the small intestine prior to reaching the hindgut.

To help reduce the risks for gastric ulcer development and digestive upset due to starch spillover into the hindgut, equine nutritionists recommend limiting starch to less than 1 gram per kilogram body weight per meal. Corn or any other high-calorie feedstuff is not recommended for horses that are obese or those suffering from or at risk for laminitis, equine metabolic dysfunction, or muscle disorders (e.g., polysaccharide storage myopathy) requiring a low-starch diet.

Myth 6: Giving water to a hot horse will cause him to colic.

“Everyone in the horse world knows that a horse will colic if he drinks water when he’s hot and tired after exercise.”  

It is vital that any horse performing intense exercise in hot conditions have access to water as often as possible. This is the quickest and best way to replenish fluids and electrolytes lost in sweat. Waiting for the horse to cool down might exacerbate dehydration.

Anna O’Brien, DVM, a large animal veterinarian in Central Maryland, attributes the hot horse myth to Anna Sewell’s classic book Black Beauty. In one scene, Black Beauty is ridden hard through the night in a storm. Brought back to the stable by his young rider without a proper cool-down, the horse is given ice-cold water from a bucket to gulp down and is left steaming in his stall. Later that night, Black Beauty colics, presumably from the cold water.

“Like human athletes, after strenuous exercise a horse must be allowed to cool down properly,” says O’Brien. This allows the heart rate, respiratory rate, and body temperature to gradually return to normal and keeps the muscles moving to flush out lactic acid that builds up during very intense exercise.

An inadequte cool-down can cause severe dehydration and coliclike signs in an exhausted horse, as vital electrolytes are depleted through sweat.

“If the Black Beauty scenario occurred in real life, I’d bet he was going through (the neuromuscular condition tying-up or severe dehydration) caused by improper cooling, dehydration, and/or overuse, not the water he was given,” O’Brien says. No matter the scenario, horses always need free-choice access to as much clean water as their bodies require.

Myth 7: Corn oil acts as a lubricant by coating the GI tract.

“I feed my horse corn oil to help keep his digestive system flowing and prevent colic.”

Amanda Paulhamus, DVM, PAS, of Paulhamus Veterinary Associates, in Linden, Pennsylvania, frequently rebuts this myth for horse owners. “Horses actually digest corn oil, and it adds calories to the diet but does nothing to lubricate the GI tract.” We know that horses metabolize corn oil readily in the small intestine, leaving very little left over to coat any part of the large intestine, let alone prevent colic.

On the other hand, mineral oil is not broken down or absorbed in the digestive tract. If a veterinarian suspects a horse is suffering from impaction colic, he or she often administers a mineral oil and water mix via nasogastric tube directly into the horse’s stomach, and from there it travels through the digestive tract as an effective lubricant.

Take-Home Message

Science has revealed massive quantities of horse care information in the past several centuries, which we’ve used to better our understanding of feeding horses. Yet myths surrounding nutrition remain prevalent. Thankfully, we have the science to many times refute the falsehoods.

Ask an equine nutritionist or veterinarian to answer the tough questions and provide you with science-based feeding recommendations.