Horse Nutrition Guide: Feed, Forage & Supplements

A balanced horse diet starts with quality forage, clean water, and the right minerals. Most horses in light work don't even need grain if their hay is decent. That one fact alone could save you hundreds of dollars a year.

But feeding horses well goes deeper than just tossing hay over a fence. Your horse's digestive tract is a finely tuned fermentation machine. Mess with it carelessly, and you'll pay for it in vet bills.

Horses are built to graze. They evolved spending 16 to 18 hours a day wandering and nibbling small amounts of forage. Their whole gut depends on this pattern. When we stick them in stalls with two big meals a day, we're fighting biology. Understanding that tension between wild design and domestic reality is where good nutrition starts.

How Does the Equine Digestive System Influence What You Feed?

The equine digestive system is unlike anything else in the barn. Knowing how it works explains almost every feeding rule you've ever heard.

The Foregut

Your horse's stomach is shockingly small. It holds just 2 to 4 gallons, which is tiny for an animal that weighs half a ton. That's why small, frequent meals matter so much.

Here's the kicker: the stomach produces acid around the clock, whether food is in there or not. An empty stomach sits in a bath of its own acid. That's a straight line to gastric ulcers, and it's the reason long gaps between meals are a problem. Forage in the stomach acts as a physical buffer against that acid splash.

The small intestine handles starches, sugars, proteins, fats, and some vitamins and minerals. Feed moves through here quickly.

The Hindgut

This is where everything gets interesting. The cecum and large colon hold roughly 30 gallons combined, and they're packed with billions of microorganisms. These bacteria and protozoa ferment fiber from forage into volatile fatty acids, which are actually your horse's main energy source. Not grain. Fermented fiber.

Those microbes are picky roommates. Change their food supply suddenly and they revolt. A rapid diet shift can wipe out beneficial populations and let harmful ones explode, which leads to gas, colic, or laminitis. Every feed change should happen gradually over 7 to 14 days. No exceptions.

Forage: The Foundation of Everything

Forage should make up the bulk of every horse's diet. Period. For most horses, that means 1.5 to 2% of body weight per day in hay or pasture. A 1,000-pound horse needs 15 to 20 pounds of hay daily.

Why Forage Comes First

Fiber fuels the hindgut. Without enough of it, the whole system stalls. But forage does more than feed microbes:

• It keeps the gut moving, reducing impaction colic risk
• It buffers stomach acid, protecting against ulcers
• It satisfies the chewing urge and provides mental stimulation
• Fermentation generates body heat, which matters in cold weather
• It supplies baseline vitamins and minerals

Types of Hay

Not all hay is equal. What you choose affects calories, protein, and sugar content across the entire diet.

Grass hay (Timothy, orchard grass, Bermuda, Coastal, brome) is moderate in calories and protein. It works for most adult horses in light to moderate work. Timothy and orchard grass dominate in northern states, while Bermuda and Coastal are the southern staples.

Legume hay (alfalfa, clover) packs more calories, more protein, and more calcium. Hard-working horses, growing youngsters, lactating mares, and thin horses thrive on it. But easy keepers can balloon on alfalfa, and the calcium-to-phosphorus ratio needs watching.

Mixed hay blends grass and legume for a nutritional middle ground. It's a solid option when straight grass hay isn't quite enough but full alfalfa is overkill.

Evaluating Hay Quality

Good hay is green, leafy, and smells clean. Reject anything moldy, dusty, or musty. Yellow or brown hay has been sun-bleached or cut too late and has lost nutritional value. Fine stems beat thick, woody ones every time.

The best move you can make? Get a forage analysis. For $25 to $40, a lab will break down your hay's protein, fiber, sugar, starch, mineral content, and energy value. No more guessing. You'll know exactly what your hay provides and exactly where the gaps are.

Pasture

Good pasture is phenomenal forage, but it's not set-and-forget. Nutritional content swings wildly with season, weather, grass species, and management.

Spring grass is loaded with sugars (non-structural carbohydrates, or NSC). For horses with Equine Metabolic Syndrome or Cushing's disease (PPID), that sugar surge can trigger laminitis. These horses need restricted or managed grazing, especially during peak growth in spring and fall.

Concentrates: Does Your Horse Actually Need Grain?

Many horses don't need grain at all. That surprises people, because barn culture treats grain as a given. But a horse in light work or maintenance, one that isn't growing, pregnant, or in heavy training, often does just fine on quality forage plus a vitamin-mineral supplement.

Concentrates earn their place when forage alone can't meet energy or nutrient demands. That includes horses in moderate to heavy work, growing youngsters, pregnant or lactating mares, underweight horses, and seniors who struggle to process fiber efficiently.

Types of Concentrates

Commercial feeds (pelleted or textured) are formulated to be nutritionally balanced at the recommended feeding rate. That last part matters. Feed half the suggested amount and your horse gets half the intended vitamins and minerals. You'd need a separate supplement to close that gap.

Straight grains (oats, corn, barley) deliver energy but aren't balanced on their own. Oats are the safest option because of their higher fiber content. Corn is energy-dense but starch-heavy, and overfeeding it invites hindgut trouble.

Beet pulp is really a forage substitute. It's packed with digestible fiber and calories, low in sugar (unsweetened), and provides energy through fermentation rather than starch. Soak it before feeding to minimize any choke risk.

Rice bran and fat supplements add calories without the starch load. Fat delivers about 2.25 times more energy per gram than carbohydrates, making it an efficient choice for weight gain or performance support.

Feeding Rules for Concentrates

• Feed by weight, not volume. A scoop of oats and a scoop of corn contain wildly different calorie loads. Weigh your feed.
• Keep meals small. No more than 4 to 5 pounds of grain per feeding for a 1,000-pound horse. If your horse needs more, split it into three or more meals.
• Feed hay before grain. Hay in the stomach slows grain passage through the foregut, improving starch digestion in the small intestine and reducing starch overflow into the hindgut.
• Change amounts gradually. Increase or decrease by no more than half a pound per day.

Water: The Nutrient Everyone Forgets

A resting horse drinks 5 to 10 gallons of water daily. In summer heat or during hard work, that number can double or triple. Water drives digestion, temperature regulation, joint lubrication, and waste removal.

Dehydration is a direct path to impaction colic. When water intake drops, gut contents dry out and compact into a blockage. It's the most common type of colic, and it's largely preventable.

Tips for Encouraging Water Intake

• Keep water clean and fresh. Horses are fussy drinkers and will cut back on stale or dirty water.
• Offer lukewarm water in winter. Research shows horses drink significantly more when water is 45 to 65 degrees Fahrenheit versus near-freezing.
• Provide loose salt or a salt block to stimulate thirst.
• When traveling, bring water from home or flavor both home and travel water with a splash of apple juice so the taste stays consistent.
• Check buckets and automatic waterers every single day.

Vitamins and Minerals: Filling the Gaps

Even excellent forage leaves nutritional holes. Here are the ones that matter most.

Salt (Sodium Chloride)

Horses need 1 to 2 ounces of salt daily at maintenance, and more during heat or heavy work. Hay and grain are naturally low in sodium. Free-choice salt blocks work, but many horses won't lick enough. Adding loose salt to the daily feed is more reliable.

Vitamin E

Fresh pasture is loaded with vitamin E. Hay is not. Within weeks of cutting, most of the vitamin E in hay is gone. Horses without regular pasture access almost always need supplementation, especially those with neurological concerns or heavy training loads. Natural vitamin E (d-alpha-tocopherol) absorbs far better than synthetic versions.

Selenium

Selenium levels in forage depend entirely on soil content, which varies wildly by region. Much of the eastern U.S. is selenium-deficient. Selenium and vitamin E work as a team on the antioxidant front, and deficiency can cause white muscle disease in foals and poor immune function in adults. But selenium toxicity is also real and dangerous, so base your supplementation on forage analysis and regional data, not guesses.

Copper and Zinc

These trace minerals are commonly short in many forages. They drive hoof quality, coat health, immune function, and connective tissue integrity. Most nutritionists recommend supplementing copper and zinc at roughly a 1:3 ratio (copper to zinc).

Calcium and Phosphorus

The total diet should have a calcium-to-phosphorus ratio between 1.5:1 and 2:1. Alfalfa runs high in calcium while grains lean toward phosphorus. An inverted ratio (more phosphorus than calcium) sustained over time leads to bone problems. Keep an eye on this one.

Supplements: What Actually Works?

The supplement aisle is overwhelming. Some products have real science behind them. Others are mostly marketing with a nice label.

Supplements with Strong Evidence

• Biotin (15 to 20 mg/day) improves hoof wall quality, but you need 6 to 9 months of consistent use to see results.
• Vitamin E is essential for horses without pasture. Well-supported for muscle and neurological health.
• Omega-3 fatty acids from flaxseed or fish oil offer anti-inflammatory benefits, better coat quality, and joint support.
• Electrolytes replace sodium, chloride, potassium, calcium, and magnesium lost in sweat. Critical for horses in heavy work or hot climates.
• Probiotics and prebiotics show some benefit during digestive stress from antibiotics, travel, or feed changes.

Supplements with Limited Evidence

• Joint supplements (glucosamine, chondroitin, hyaluronic acid) are wildly popular, but research results are mixed. Oral bioavailability is questionable for some ingredients. Some horses respond well. Others show zero change.
• Calming supplements based on magnesium, tryptophan, or thiamine have limited scientific backing. Response varies by individual.

General Supplement Advice

• Fix the base diet first. No supplement compensates for bad forage or an unbalanced ration.
• Watch for ingredient overlap when stacking multiple products. Over-supplementing selenium or iron can be toxic.
• Choose products backed by published research, not just testimonials and pretty packaging.
• Give supplements time. Most need 30 to 90 days before you can judge results. Biotin needs 6 to 9 months.

Feeding for Specific Situations

The Easy Keeper

Some horses gain weight on air alone. These metabolically efficient types are prone to obesity, insulin resistance, and laminitis.

• Feed low-NSC grass hay. Test it and aim for NSC below 10 to 12%.
• Soak hay for 30 to 60 minutes to leach out sugars (reduces NSC by roughly 30%).
• Use slow feeders or hay nets to stretch eating time.
• Skip grain entirely. Use a ration balancer for vitamins and minerals instead.
• Manage pasture access carefully during spring and fall sugar surges.
• Exercise is your best tool. Movement improves insulin sensitivity better than any feed change.

The Hard Keeper

Before dumping more grain into a thin horse's bucket, rule out medical causes. Dental problems, parasites, ulcers, and PPID all kill weight gain. Have your vet check first.

• Maximize forage intake with the best quality hay you can find, free-choice.
• Add calorie-dense, low-starch options like beet pulp, rice bran, vegetable oil, or high-fat commercial feeds.
• Feed smaller meals more frequently to improve digestive efficiency.
• Consider alfalfa or a grass-alfalfa mix for extra calories and protein.
• Create a calm feeding environment. Stress and competition at the feeder tank intake fast.

Senior Horses

Older horses face a different set of nutritional challenges. Worn teeth make chewing long-stem hay difficult. Digestive efficiency declines. Cushing's disease (PPID) shows up frequently in seniors and messes with metabolism across the board.

• Check teeth every 6 to 12 months and adjust feed form accordingly.
• If the horse can't handle hay anymore, switch to soaked hay cubes, chopped hay, or a complete senior feed designed to replace forage entirely.
• Senior feeds typically contain higher fiber, more digestible ingredients, and boosted vitamin and mineral levels.
• Watch body condition closely. Weight loss in old horses creeps up on you if you're not paying attention.

Body Condition Scoring: Is Your Horse the Right Weight?

The Henneke Body Condition Scoring system rates horses from 1 (emaciated) to 9 (extremely obese) based on fat deposits in six areas: neck, withers, behind the shoulder, over the ribs, along the back, and at the tailhead.

Most adult horses should fall between 4.5 and 6. Below 4 means the horse needs more calories. Above 7 means obesity and increased health risks. Learning to score takes practice, but your vet or an equine nutritionist can walk you through it during a farm call.

What Are the Most Common Horse Feeding Mistakes?

Even experienced horse owners slip up on nutrition. Here are the mistakes I see most often:

1. Too much grain, not enough hay. This is the big one. Grain supplements forage. It doesn't replace it.
2. Sudden feed changes. Transition over 7 to 14 days. Always.
3. Feeding by the scoop instead of the scale. Different feeds have wildly different densities. Weigh everything.
4. Neglecting water. Check supply and cleanliness daily.
5. Over-supplementing. More is not better. Excess minerals cause toxicity or block absorption of other nutrients.
6. Skipping forage analysis. Without it, you're guessing.
7. Feeding bad hay. Moldy or dusty hay isn't worth the risk. Throw it out.
8. Treating every horse the same. Individual needs vary enormously based on age, breed, workload, and metabolism.

Building Your Horse's Diet: A Step-by-Step Approach

Want a feeding plan that actually works? Follow this order:

1. Start with forage. Figure out how much hay or pasture your horse needs (1.5 to 2% of body weight for most horses).
2. Get a forage analysis. Know what your hay delivers in energy, protein, and minerals.
3. Assess the horse. Factor in age, workload, body condition, and any health issues.
4. Fill nutritional gaps. Use a vitamin-mineral supplement or ration balancer targeted to the deficiencies your forage analysis revealed.
5. Add energy if needed. If forage alone doesn't maintain condition or support the workload, bring in concentrates, beet pulp, or fat.
6. Provide salt and fresh water at all times.
7. Monitor and adjust. Body condition, coat quality, energy level, and hoof health tell you whether the diet is working. Tweak as seasons and workload change.

Frequently Asked Questions

How much hay should a horse eat per day?

Most horses need 1.5 to 2% of their body weight in forage daily. For a 1,000-pound horse, that's 15 to 20 pounds of hay. Horses in heavy work, lactating mares, and growing youngsters may need the higher end of that range or additional calories from concentrates.

Can I feed my horse without grain?

Absolutely. Many horses thrive on forage alone plus a ration balancer or vitamin-mineral supplement. Grain becomes necessary only when forage can't meet the horse's energy demands, such as during heavy training, growth, pregnancy, or lactation.

How do I know if my hay is good quality?

Look for green color, leafy texture, fine stems, and a clean smell. Avoid anything moldy, dusty, yellow, or overly stemmy. The most reliable method is a forage analysis from a lab, which costs $25 to $40 and gives you exact nutritional values.

Why is forage analysis important?

Two bales of Timothy hay from different fields can have completely different protein, sugar, and mineral profiles. Without testing, you're guessing at what your horse is actually getting. A forage analysis lets you supplement precisely instead of throwing money at problems that may not exist.

How often should I change my horse's diet?

Only when something needs to change, like a new hay source, shifting workload, weight fluctuations, or seasonal transitions. When you do make changes, do it gradually over 7 to 14 days to protect the hindgut microbiome.

Track Your Horse's Nutrition with Inside the Equine

Keeping tabs on feed amounts, weight trends, and supplement schedules gets complicated fast, especially with multiple horses.

Inside the Equine's My Horse feature gives you one place to log diets, track body condition over time, and set reminders for feed adjustments. Pair it with the Encyclopedia for deeper dives into specific nutrients and conditions, and you've got the tools to make smart feeding decisions every day.

Good nutrition isn't about the fanciest feed or the trendiest supplement. It's about understanding what your individual horse needs and delivering it consistently. Start with forage. Fill the gaps. Pay attention. Your horse will tell you when you've got it right.

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Feeding horses well blends science with observation and a healthy dose of common sense. The research tells us what they need. Daily observation tells us how they're responding. And common sense keeps us from overcomplicating something that, at its core, is straightforward: good forage, clean water, balanced minerals, and a watchful eye.

Last reviewed: March 2026

Forage is the foundation of every feeding program. Get the specifics in our forage requirements guide and learn how the gut processes fiber in our cecum and hindgut fermentation article.

Sources

• National Research Council. Nutrient Requirements of Horses, 6th Revised Edition. National Academies Press, 2007.
• Texas A&M AgriLife Extension. "Horse Nutrition." agrilifeextension.tamu.edu
• UC Davis Center for Equine Health. "Feeding the Horse." ceh.vetmed.ucdavis.edu
• AAEP. "Nutrition for Horses." aaep.org
• Merck Veterinary Manual. "Nutritional Requirements of Horses." merckvetmanual.com