Horse nutrition guide: hay, concentrates, supplements, and common mistakes
The horse is probably the domesticated animal whose nutrition is simplest to describe in one sentence - and most difficult to get right in practice. The sentence: a hindgut-fermenting herbivore, evolved to graze continuously, whose digestive system was never designed for concentrated cereals. The difficulty: in the reality of 21st-century European stables, around 60 to 70 percent of horses are fed suboptimally according to data from the French National Institute for Agricultural Research (INRAE).
This guide covers the full spectrum: digestive biology, actual requirements by activity level, classic mistakes (some of them lethal), supplements that work and those that merely lighten your wallet, and the main equine nutrition brands available in Europe.
Version française disponible : alimentation du cheval - guide complet.
Equine digestive biology: everything starts here
The horse (Equus caballus) is a monogastric hindgut fermenter. Unlike ruminants (cattle, sheep, goats), which ferment plant material in a multi-compartment stomach before the small intestine, the horse ferments in the caecum and colon - that is, after the small intestine. This digestive architecture has three major practical consequences that every owner must internalise.
First: the horse's stomach is small. Approximately 8 to 15 litres of capacity for a 500 kg horse - disproportionately small for its body size. The equine stomach empties continuously during feeding and is never designed to be filled to capacity. In the wild, the horse spends 16 to 18 hours per day grazing small amounts of coarse forage. When fed in two large concentrate meals per day (as many stables still do), this creates a violent filling of a stomach designed for continuity, with the resulting risk of gastric colic.
Second: the horse cannot vomit. The cardia (valve between the oesophagus and stomach) is anatomically locked. A horse that consumes too rapidly or in excessive quantity cannot expel the excess. Gastric pressure must move towards the intestine, which can cause ruptures, dilatations, or severe colic.
Third: hindgut fermentation is fragile. The caecum and colon harbour a complex bacterial microbiome that ferments cellulose from forage. If a large amount of starch (via concentrated cereals) is introduced abruptly, some arrives undigested in the colon, disrupts the microbiome, produces lactic acids, and releases endotoxins. Result: laminitis, colic, dysbiosis. This mechanism is the primary cause of diet-induced laminitis.
Hay: the absolute non-negotiable foundation
The fundamental principle of equine nutrition is not negotiable: hay (or pasture) must constitute 100 percent of the dietary base, with concentrates as a supplement only when activity demands it.
The recommended quantity is 1.5 to 2 percent of bodyweight per day in dry forage. For an average 500 kg horse, this means 7.5 to 10 kg of hay per day. For a 200 kg pony, 3 to 4 kg.
| Horse weight | Minimum forage/day | Recommended forage/day |
|---|---|---|
| 200 kg (pony) | 3.0 kg | 3.5-4.0 kg |
| 350 kg (light horse) | 5.3 kg | 6.0-7.0 kg |
| 500 kg (standard horse) | 7.5 kg | 8.5-10.0 kg |
| 650 kg (heavy horse) | 9.8 kg | 11.0-13.0 kg |
Hay quality: what actually matters
Not all hays are equal. The parameters that matter for horses:
Energy value (Horse Feed Units / UFC): a good first-cut meadow hay can reach 0.70-0.85 UFC/kg. A second-cut regrowth hay can reach 0.90 UFC/kg but with higher protein and soluble carbohydrates - less suited to laminitis-prone horses.
Total water-soluble carbohydrates (WSC): critical for horses at risk of laminitis or suffering from equine metabolic syndrome (EMS). The recommended threshold for "metabolic" horses is below 10-12 percent WSC (fructan plus starch plus simple sugars) on dry matter basis. Hay cut in the morning after a cold night contains less fructan than hay cut in early afternoon - a practical detail that few owners know.
Dust and mould. Mouldy or very dusty hay causes respiratory irritation and digestive issues. The simple test: rub a handful of hay in your hands - if a cloud of dust rises, the hay is not suitable. Soaking hay in water (30 minutes) reduces dust by approximately 90 percent. Steaming (45 minutes of steam treatment) is more effective and better preserves nutritional value.
Hay vs silage vs haylage. Silage (fermented moist hay) is rarely used for horses - secondary fermentations produce organic acids and sometimes toxins (listeria in poorly sealed bales) incompatible with equine physiology. Haylage (hay baled at 40-50 percent moisture) is used but requires vigilance on bale integrity.
Pasture: opportunity and trap
Access to a field seems the natural ideal for a horse. This is generally true, with two important nuances.
Seasonal grass variation. In spring and autumn, young grass is very high in fructans (fermentable carbohydrates). For a healthy horse with good activity levels, this is often manageable. For an overweight horse, a metabolic pony, or an animal predisposed to laminitis, spring grass can trigger a laminitis episode within 24 to 48 hours. In these cases, limited paddock access (a few hours in the early morning, when fructan content is lowest) or a grazing muzzle is recommended.
Grass density. One hectare of pasture can feed 1 to 1.5 horses in summer. Below this surface area, the horse does not obtain enough grass to cover forage needs and must be supplemented with hay even during the grazing season.
Concentrates: when, how much, which
Concentrates (cereals, compound pellets, dried sugar beet) are not a necessity for a leisure horse with moderate activity fed good hay. They become necessary when forage alone no longer covers energy requirements from work.
Basic rule by activity level
| Activity level | Examples | Forage | Concentrates |
|---|---|---|---|
| Rest (box, field) | Unridden horse, foal at pasture | 100 percent | 0 |
| Light (1-3h/week) | Hacks, flat terrain | 90-95 percent | 5-10 percent |
| Moderate (3-5h/week) | Club riding, weekly lessons | 75-85 percent | 15-25 percent |
| Intensive (5-10h/week) | Regular competition | 60-70 percent | 30-40 percent |
| Elite (daily work) | National/international competition | 50-60 percent | 40-50 percent |
The "50 percent minimum forage" rule must never be crossed, even in the highest-level competition horse. Below this proportion, the risk of gastric ulcers, colic, and laminitis increases significantly.
Cereals: benefits and risks
Barley is the most suitable cereal for horses. Its starch is 25-30 percent fermentable in the small intestine (versus 60-70 percent for maize), reducing the amount of intact starch reaching the colon. It is fed rolled or steam-rolled to improve digestibility.
Oats are the traditional horse cereal. Lower energy density than maize or barley, but better physiological compatibility thanks to fibre content (oat hull included in the grain) that slows digestion. Classically associated with a "sharper" temperament in some sport horses - an effect explained by slight nervous system stimulation via certain oat amino acids.
Maize is the most energy-dense concentrate but the most risky. Very high starch content (65-70 percent), highly fermentable in the colon. Feed only in small quantities, rolled, never whole.
Compound pellets are generally preferable to raw cereals for non-professional owners. Their formulation is species-calibrated with integrated mineral and vitamin balance, their starch is often pre-cooked (better digestibility), and the risk of ration error is lower. Brands such as Dodson & Horrell, Spillers, and Cavalor offer ranges adapted to all activity levels with transparent technical specifications.
Colic: the number one enemy
Colic is the leading cause of death in domestic horses in Europe. It covers a range of abdominal pain syndromes from transient discomfort (spasmodic colic) to surgical emergency (intestinal torsion). The figures: approximately 10 percent of horses experience at least one colic episode per year, and mortality across all colic types is estimated at 1 to 5 percent.
Dietary factors that increase colic risk:
Insufficient forage or irregular distribution. A horse that fasts for more than 6 consecutive hours (during transport, stable rest without continuous hay access, etc.) has an elevated risk of spasmodic colic and right dorsal displacement.
Abrupt dietary changes. Any ration modification (new hay supplier, new cut, different composition forage) must occur over a minimum of 10 to 14 days by progressively mixing old and new hay. The horse's intestinal microbiome adapts slowly.
Excessive concentrate quantity in a single meal. A concentrate meal should never exceed 2 kg for a 500 kg horse. Beyond this, undigested starch in the small intestine overflows to the colon.
Dehydration. Impaction colic (retention colic) is favoured by insufficient water intake, particularly in winter when trough water is cold. A 500 kg horse must consume 25 to 50 litres of water per day at rest, up to 80 litres under exertion in hot conditions.
Laminitis: the underestimated risk
Laminitis is an inflammation of the laminar tissue of the hoof (the lamellae between the hoof wall and the pedal bone) that can lead to rotation or sinking of the coffin bone - irreversible if untreated. It is linked to episodes of vascular overload in the hoof, often triggered by dietary causes.
Horses and ponies most at risk: obese ponies, horses with Cushing's syndrome (PPID), horses suffering from equine metabolic syndrome (insulin resistance), and horses of all breeds with access to rich pasture in spring.
The number one warning sign: a horse that "spares" its front legs, lies down longer than usual, or shows detectable heat in the hooves must be seen by a vet urgently. Every hour counts.
Dietary prevention: limit pasture access for at-risk animals during spring, never exceed recommended concentrate rations, provide low water-soluble carbohydrate hay for metabolic horses.
Water: the forgotten nutrient
Water is the most important nutrient in equine nutrition - and the most often neglected in ration calculations. A 500 kg horse at rest consumes 25 to 50 litres of water per day. In summer, under exertion, this figure can reach 60 to 80 litres.
Practical implications:
- An automatic trough must deliver at least 10 litres per minute for a single box
- Cold water in winter (below 5 degrees C) is consumed in lesser quantities by some horses - risk of impaction colic
- Good quality hay contributes to hydration (15-20 percent water in dried hay, up to 80 percent in fresh grass)
- A salt lick must be available at all times to compensate for mineral losses through sweating
Electrolytes for sport horses
A horse that sweats heavily (prolonged effort, transport, summer heat) loses electrolytes - primarily sodium, chloride, potassium, calcium, and magnesium. Equine sweat is hypertonic relative to plasma: it contains more sodium and chloride than human sweat, meaning electrolyte losses are proportionally higher.
Signs of electrolyte deficit: muscle cramps, abnormal fatigue, convulsions in severe deficiency, "thumps" (synchronous diaphragmatic flutter - rhythmic abdominal quivering linked to hypocalcaemia and hyponatraemia).
Electrolyte supplementation is justified for horses working more than 1 hour per day in summer, for endurance competitions (more than 20 km), and during prolonged transport. Commercial products (powders dissolved in water or mash) are easier to dose correctly than homemade supplementation with table salt alone, which does not cover potassium and magnesium.
Mineral and vitamin supplements
A horse fed on hay alone without access to diverse pastures may have deficits in certain minerals and vitamins depending on local soil composition.
Minerals to monitor
Selenium. Large areas of Europe (notably Central and Western France, Great Britain, Sweden) have selenium-poor soils. A selenium-deficient horse shows muscular disorders (nutritional myopathy), fatigue, and reduced infection resistance. Annual blood testing is recommended in at-risk areas. Important: selenium is toxic in excess - supplement only after blood testing and under veterinary supervision.
Zinc and copper. Often in unbalanced ratio in intensive hays. Excess zinc inhibits copper absorption. Copper deficiencies affect cartilage quality (joint problems in growing foals), coat pigmentation, and immunity.
Magnesium. Involved in neuromuscular regulation. "Nervous" horses or those with unexplained muscle cramps may benefit from supplementation. Blood testing before any supplementation.
Vitamins
Vitamin E. Muscular and neurological antioxidant. Produced naturally in fresh grass, absent from dried hay (degrades at harvest and during storage). A horse living primarily in a box with limited access to fresh pasture may develop vitamin E deficits, especially under high activity. Natural vitamin E supplementation (d-alpha-tocopherol) is preferred over synthetic (dl-alpha-tocopherol) for better bioavailability.
Vitamin D. Synthesised through sun exposure. Horses living primarily under shelter in winter in northern countries may be deficient. Be cautious about overdosing - toxic in excess.
Biotin. Vitamin B7, involved in hoof horn quality. Biotin supplementation (minimum 20 mg/day for 9 to 12 months for a 500 kg horse) improves horn quality in horses with brittle or fragile hooves. Results visible after 6 to 9 months (time for a complete hoof to grow).
Major equine nutrition brands
| Brand | Origin | Strengths | Flagship range |
|---|---|---|---|
| Dodson & Horrell | United Kingdom | Formulation transparency, medical range | Build-Up Conditioning Mix |
| Spillers | UK (Mars) | Wide distribution, metabolic formulas | Happy Hoof (low starch) |
| Cavalor | Belgium | Sport innovation, scientific documentation | Endurix (endurance) |
| Pferdesport Menne | Germany | German quality, targeted supplements | Hippo-Tisin (recovery) |
| Pavo | Netherlands | Value for money, wide range | Pavo Care4Life |
| Equifirst | Netherlands | Natural ingredients, simplicity | Fiber Mix |
Dodson & Horrell stands out for the transparency of its technical specifications - one of the rare brands to publish amino acid profiles of its products and independent efficacy studies.
Spillers (owned by Mars Petcare, like Royal Canin) is criticised by some enthusiasts for belonging to a large food conglomerate, but its Happy Hoof range (very low starch and sugars, specific to metabolic horses) is recognised by European vets specialising in equine medicine.
Cavalor invests in sports research - their nutrition team regularly publishes in veterinary sports medicine journals. For competition horses, their Endurix (endurance) and Optiforce (showjumping/dressage) ranges are supported by field efficacy data.
Classic mistakes to absolutely avoid
Mistake 1: two large concentrate meals per day. The horse's stomach is built for continuity. Two large meals 12 hours apart create long fasting periods (risk of gastric ulcers - prevalence of 60-90 percent in sport horses in Europe according to endoscopic studies) and abrupt starch flooding at each meal. Split into a minimum of 3 to 4 meals, or give small concentrate portions with continuous hay access.
Mistake 2: insufficient water in winter. Water consumption drops when trough water is too cold. Install a trough heater or check daily that water has not frozen. A short period (48-72 hours) of insufficient water intake can trigger impaction colic in a predisposed horse.
Mistake 3: abrupt hay changes. A new supplier, a new cut, forage of different composition - any change must happen over a minimum of 10 to 14 days by progressively mixing old and new hay. The caecal microbiome adapts slowly.
Mistake 4: supplementing without prior analysis. The risk is overdose, not deficiency. Selenium, vitamin D, excess copper are toxic. Before adding a mineral supplement, request a complete ration analysis (hay plus existing supplements plus water if possible) from an equine nutritionist or your vet.
Mistake 5: treating all horses the same. A 250 kg pony, a 600 kg KWPN, and a pregnant mare have radically different needs. Generic ration guidelines are starting points, not prescriptions.
Frequently asked questions
Can horses eat apples and carrots?
Yes, but in moderation and with awareness. Apples and carrots are acceptable treats (not nutritional supplements). For a 500 kg horse, 1 to 2 apples or a few carrots per day causes no health issue for a healthy horse. Caution for metabolic horses or laminitis-prone ones: the simple sugar content of apples is significant. Cut into small pieces to avoid choking risk.
Does a hay net really slow consumption?
Yes, documented. A horse fed hay in a small-hole net (3-4 cm mesh) consumes its hay 30 to 50 percent more slowly than the same hay given on the floor or in an open rack. It also spends more time in the grazing position - closer to natural behaviour. The effect on digestive health is positive: fewer fasting periods, reduced ulcer risk, better weight management for obesity-prone horses.
Salt lick or granular salt?
Both work, with differences. A free-access salt lick provides sodium on demand - the horse licks according to its needs. Granular salt in the ration allows precise dose control. For a healthy horse, a free-access salt lick is sufficient. For a sport horse or during intense heat, controlled electrolyte supplementation (powder in ration or water) is more precise.
Further reading
For owners of other species, see our species nutrition guides: rabbit nutrition guide, ferret nutrition guide, and our best dog food 2026 ranking.
Our horse food rankings page brings together rated products in our database.
Sources
- INRAE (Institut National de la Recherche Agronomique) - Horse nutrition recommendations (2024) : inrae.fr
- National Research Council (NRC) - Nutrient Requirements of Horses, 6th edition (2007), National Academies Press : nap.nationalacademies.org
- Luthersson N. et al. - Risk factors associated with equine gastric ulcer syndrome in the Danish horse population, Equine Veterinary Journal (2009) : pubmed.ncbi.nlm.nih.gov
- Geor R.J. - Pasture-associated laminitis, Veterinary Clinics of North America: Equine Practice (2009) : pubmed.ncbi.nlm.nih.gov
- Spillers - Horse feeding guide (2025) : spillers-feeds.com
- Dodson & Horrell - Nutritional guidance for performance horses (2024) : dodsonandhorrell.com
- Sophie Lefevre, Species nutritionist, PetFoodRate