horse nutrition guide — Nutrition is the foundation of equine health, influencing everything from body condition and athletic performance to immune function and longevity. The horse is a hindgut fermenter whose digestive system evolved to process a continuous intake of fibrous forage over the course of the day. Understanding this fundamental biological reality is the key to feeding horses correctly. Many of the most common equine health problems, including colic, laminitis, and gastric ulcers, are directly or indirectly related to feeding practices that deviate from the horse’s natural feeding pattern. This comprehensive guide covers the principles of equine nutrition, the roles of forage and concentrates, the appropriate use of supplements, and dietary management across different life stages and activity levels.
Context of the horse nutrition guide
The Equine Digestive System: Understanding the Machinery
The horse’s digestive system is exquisitely adapted to a diet of grasses and other fibrous vegetation consumed in small amounts throughout the day. Unlike ruminants such as cattle, which have a four-chambered stomach and chew the cud, horses are non-ruminant herbivores with a relatively small stomach and a large, complex hindgut where microbial fermentation of fiber occurs.
The stomach of a horse is surprisingly small relative to the animal’s size, with a capacity of only two to four gallons. In the wild, a horse’s stomach is never empty, as the horse grazes for sixteen to eighteen hours daily. The stomach continuously secretes hydrochloric acid, and without the buffering effect of saliva produced during chewing, the stomach lining is vulnerable to acid damage. This is why horses on restricted feeding schedules, particularly those fed large meals of concentrates with long periods without food between them, are at high risk for gastric ulcers.
The small intestine is where enzymatic digestion of proteins, simple carbohydrates, and fats occurs. The small intestine has a limited capacity for processing starch and sugar. When large meals of high-starch concentrates are fed, undigested starch can spill over into the hindgut.
The hindgut, consisting of the cecum and large colon, is where the microbial fermentation of fiber occurs. A diverse population of bacteria, protozoa, and fungi break down cellulose and other complex carbohydrates into volatile fatty acids, which are absorbed and used as a primary energy source. The hindgut microbiome is sensitive to dietary changes, and sudden alterations in diet, particularly the introduction of high-starch feeds, can disrupt the microbial balance, leading to colic and laminitis.
Forage: The Indispensable Foundation
Forage must form the foundation of every horse’s diet. The minimum recommended forage intake is one to one and a half percent of the horse’s body weight in dry matter per day. For a one thousand pound horse, this translates to ten to fifteen pounds of hay or equivalent pasture daily. Many horses do well on forage alone if it is of adequate quality and quantity, and concentrates are only necessary when forage cannot meet the horse’s energy and nutrient requirements.
Types of Forage
Pasture is the most natural forage source for horses. The nutritional quality of pasture varies dramatically with the season, the plant species present, the soil fertility, and the grazing management. Lush, rapidly growing spring pasture is high in sugars and can trigger laminitis in susceptible horses. Mature, stemmy summer pasture is lower in nutritional value. A grazing muzzle can limit intake for horses that need to be on pasture but cannot handle unrestricted access.
Grass hay, including timothy, orchard grass, brome, and Bermuda grass, is the standard forage for horses. The nutritional quality of hay depends on the plant species, the stage of maturity at harvest, and the harvesting and storage conditions. Early-cut hay is more nutritious but also higher in sugars. Late-cut hay is lower in nutritional value but higher in fiber.
Legume hay, primarily alfalfa (lucerne) and clover, is higher in protein and calcium than grass hay. Alfalfa is an excellent forage for growing horses, lactating mares, and horses with high energy requirements. However, its high calcium and protein content may not be appropriate for all horses, and it is more calorie-dense than grass hay, requiring careful portion control for easy keepers.
Hay Quality Assessment
Good quality hay should be green, leafy, and sweet-smelling. It should be free of mold, dust, weeds, and foreign objects. Moldy hay can cause colic and respiratory disease and should never be fed. Dusty hay can trigger equine asthma, particularly in horses with respiratory sensitivity. Hay that was baled too wet may have undergone heating and caramelization, which reduces its nutritional value and can make it unpalatable.
Hay analysis provides objective information about the nutritional content, including crude protein, fiber fractions, and mineral content. This information allows for informed decisions about whether supplementation is necessary and what type of supplement is appropriate.
Feeding Forage
Horses should have access to forage throughout the day and night. Prolonged periods without forage, defined as more than four to five hours, increase the risk of gastric ulcers and stereotypical behaviors such as cribbing and weaving. Slow-feed hay nets and hay feeders can extend the time it takes for a horse to consume its hay ration, more closely mimicking natural grazing patterns.
Concentrates: When and How to Feed
Concentrates, including grains and commercially formulated feeds, are energy-dense feeds that supplement forage when the horse’s energy requirements exceed what forage alone can provide. They should be viewed as supplements to the forage base, not as the primary feed.
When Are Concentrates Necessary?
Concentrates may be necessary for horses with high energy demands, including horses in intense athletic training, lactating mares, and growing foals; senior horses with poor dentition that cannot effectively chew hay; hard keepers who struggle to maintain body condition on forage alone; and horses with limited access to quality forage.
The vast majority of pleasure horses and horses in light work do not require concentrates and do well on forage alone, perhaps with a ration balancer to provide vitamins and minerals.
Types of Concentrates
Whole grains, including oats, corn, and barley, are traditional horse feeds that are high in starch. Oats are the safest whole grain for horses, as their starch is more digestible in the small intestine than that of corn or barley. Whole grains should be processed by crimping, rolling, or steam-flaking to improve digestibility.
Commercial textured or pelleted feeds are formulated to provide balanced nutrition. They are available in formulations for different life stages and activity levels, from maintenance to performance. These feeds are more nutritionally complete than straight grains and reduce the risk of nutrient imbalances.
Complete feeds are formulated to be fed as the sole ration, providing all necessary fiber in addition to concentrates. They are useful for senior horses with poor teeth who cannot consume hay effectively.
Ration balancers are low-feeding-rate products that provide concentrated protein, vitamins, and minerals. They are fed in small amounts, typically one to two pounds daily, to horses on forage-only diets to ensure that micronutrient requirements are met without adding significant calories.
Feeding Concentrates Safely
Concentrates should be divided into multiple small meals rather than one or two large meals. The horse’s small stomach and the limited capacity of the small intestine to digest starch mean that a single meal should not exceed approximately five pounds of concentrate for a one thousand pound horse, and smaller is safer.
Any change in concentrate type or amount should be made gradually over seven to fourteen days, allowing the hindgut microbiome time to adapt. Sudden changes in concentrate feeding are a common cause of colic and laminitis.
Grain should be stored in secure, horse-proof containers. Accidental access to large quantities of grain can cause grain overload, a life-threatening condition characterized by severe colic, laminitis, and endotoxemia.
Water: The Most Essential Nutrient
Water is the most essential nutrient, and dehydration can have severe consequences for horses. A horse at maintenance in a moderate climate drinks approximately five to ten gallons of water daily, and this requirement increases dramatically with exercise, lactation, and hot weather.
Clean, fresh water should be available at all times. In cold weather, water heaters prevent freezing and encourage adequate intake, as horses drink less when water is near freezing. After exercise, a hot horse should be allowed to cool down before being offered unlimited cold water. Small amounts of water can be offered during the cooling process.
Electrolyte supplementation may be necessary for horses in heavy work, particularly in hot and humid conditions, but it is not a substitute for adequate water intake. Electrolytes should be provided with free access to water.
Body Condition Scoring
Body condition scoring is a practical tool for assessing whether a horse is at a healthy weight. The Henneke body condition scoring system uses a scale of one to nine, with one being emaciated and nine being obese. The ideal body condition score for most horses is five to six, at which the ribs are easily felt but not visible, the withers are rounded, and the tailhead is covered with a layer of spongy fat.
Regular body condition scoring allows for adjustments to the feeding program before significant weight loss or gain occurs. Weight tapes, while not perfectly accurate, provide a useful tool for tracking changes over time.
Special Dietary Considerations
Senior Horses
Senior horses may struggle to maintain body condition due to poor dentition, decreased digestive efficiency, and underlying health conditions. Senior feeds that are easily chewed and highly digestible, including complete feeds and soaked hay cubes or pellets, can help maintain weight. Senior horses should have their teeth examined at least annually, and dental problems should be addressed to maximize their ability to utilize feed.
Growing Horses
Growing horses, from weanlings through yearlings, have high nutritional demands to support bone and muscle development. Balanced nutrition with appropriate levels of protein, energy, calcium, and phosphorus is critical. Overfeeding energy, which leads to rapid growth, is a risk factor for developmental orthopedic disease. Growing horses should be monitored closely and their diets adjusted to support steady, moderate growth.
Horses Prone to Laminitis
Horses with equine metabolic syndrome, a history of laminitis, or a predisposition to laminitis require careful dietary management. These horses should be fed low-sugar, low-starch forage, ideally with a hay analysis to verify the non-structural carbohydrate (NSC) content, which should be below ten to twelve percent. Soaking hay in water for thirty to sixty minutes can reduce sugar content. Lush pasture, particularly in spring and fall, should be avoided or access should be limited with a grazing muzzle.
Supplements: Separating Need from Marketing
The equine supplement market is vast and largely unregulated, and many products are marketed with claims that are not supported by scientific evidence. Supplements should be used to address a specific, identified need, not as insurance against unspecified deficiencies.
Commonly used supplements with reasonable evidence of benefit include joint supplements containing glucosamine, chondroitin, and omega-3 fatty acids for horses with osteoarthritis; omega-3 fatty acid supplements, particularly those from flaxseed or fish oil, for anti-inflammatory effects and coat condition; probiotics and prebiotics for horses with gastrointestinal disturbances, though the evidence for their efficacy is mixed; and electrolyte supplements for horses in heavy work, particularly in hot conditions.
Supplements that are unnecessary for most horses on a balanced diet include general vitamin and mineral supplements, which can cause imbalances when added to a diet that is already adequate; biotin supplements, which may support hoof growth but require six to twelve months of supplementation to see effects; and calming supplements, most of which have little scientific evidence of efficacy.
Conclusion
Feeding horses correctly is fundamentally about respecting their evolutionary biology. A diet based on continuous access to quality forage, supplemented with concentrates only when forage cannot meet energy demands, and with water always available, supports digestive health, prevents disease, and provides the foundation for a long, healthy life. Regular body condition scoring and adjustments to the feeding program based on the individual horse’s needs, rather than following a rigid formula, are the marks of good horsemanship. For more on maintaining your horse’s health, see our Basic Horse Health and Care guide.
