Understanding Equine Nutrition — A Complete Guide for Australian Horse Owners
Feeding horses correctly is one of the most important — and most frequently misunderstood — aspects of horse ownership. Unlike dogs or cats, horses are hindgut fermenters designed to trickle-feed on low-energy forage for up to 16–18 hours per day. When we disrupt this natural feeding pattern through large grain meals, restricted forage access, or failure to account for workload and life stage, the consequences can be serious: gastric ulcers, colic, laminitis, tying-up, developmental orthopaedic disease, and poor performance.
This guide, written by Dr. Louise Cosgrove BVSc of EEVS – Exclusively Equine Veterinary Services, Regency Downs QLD, covers the fundamentals of equine nutrition to help Australian horse owners make informed, evidence-based decisions about their horse's diet.
How Much Should a Horse Eat Per Day?
The foundation of any equine feeding program is total daily dry matter (DM) intake. Horses should consume approximately 1.5–2.5% of their body weight in total feed per day. For a 500 kg horse, this equates to 7.5–12.5 kg of dry matter daily. The majority of this — at least 60–70% — should come from forage (hay or pasture). Forage provides the fibre necessary for healthy hindgut fermentation, produces saliva that buffers stomach acid, and satisfies the horse's natural drive to chew and graze.
Energy Requirements by Workload — NRC Guidelines
Digestible Energy (DE), measured in megacalories (Mcal), is the primary currency of equine nutrition. A horse's DE requirement increases significantly with workload. The table below shows approximate daily DE requirements for a 500 kg horse at different work intensities, based on NRC (2007) Nutrient Requirements of Horses guidelines — the gold standard reference used in this calculator.
| Workload Level | Daily DE (Mcal) | % Above Maintenance | Example Activity |
|---|---|---|---|
| Maintenance | 16.7 | — | Paddock rest, no ridden work |
| Light Work | 20.0 | +20% | 1–3 hrs/week, mostly walk |
| Moderate Work | 23.3 | +40% | 3–5 hrs/week, trot & canter |
| Heavy Work | 26.7 | +60% | 5+ hrs/week, competition horse |
| Intense / Racing | 33.4 | +100% | Daily hard training, racing |
Protein Requirements in Horses
Protein is essential for muscle development, tissue repair, immune function, enzyme production, and foetal development in pregnant mares. The key limiting amino acids for horses are lysine, methionine, and threonine. A 500 kg horse in moderate work requires approximately 900–1,100 g of crude protein per day. Growing horses, lactating mares, and senior horses have elevated protein requirements relative to body weight.
The Role of Forage — Hay and Pasture
Forage — whether pasture, hay, or chaff — is the single most important component of a horse's diet. High-quality grass hay (ryegrass, paspalum, meadow hay) provides approximately 8–9 Mcal of DE per kg of dry matter and 8–10% crude protein. Lucerne (alfalfa) hay is higher in both energy (9–10 Mcal/kg DM) and protein (15–22%), making it particularly valuable for horses with elevated requirements such as growing horses, lactating mares, and horses in heavy work.
Horses should never go more than 4–5 hours without access to forage. An empty stomach allows gastric acid to pool and damage the unprotected squamous region of the stomach lining, significantly increasing the risk of equine gastric ulcer syndrome (EGUS). Providing a small amount of hay 30 minutes before exercise is one of the most effective preventive measures for ulcer development.
Understanding Body Condition Score (BCS) in Horses
The Henneke Body Condition Score (BCS) system rates horses from 1 (extremely emaciated) to 9 (extremely obese) based on palpable fat deposits over six body regions: neck, withers, behind the shoulder, ribs, loin, and tailhead. An ideal BCS for most horses is 4–6. Broodmares are typically maintained at BCS 5–6 to optimise reproductive performance. Horses with a BCS below 4 require increased energy intake; those above 7 require energy restriction, particularly if they are at risk of laminitis or equine metabolic syndrome (EMS).
Special Nutritional Considerations
Horses with EMS or laminitis risk require strict management of non-structural carbohydrate (NSC) intake. Pasture should be restricted, particularly in spring and autumn when grass sugar content peaks. Hay should be tested and ideally soaked in cold water for 30–60 minutes to reduce NSC. High-starch grains and molasses-based feeds should be avoided entirely. A low-NSC hay balancer or ration balancer provides essential vitamins and minerals without excess energy.
Horses with PPID (Cushing's Disease) have altered metabolic function and may require a low-NSC diet similar to EMS horses. Regular monitoring of body condition and topline muscle mass is important, as PPID horses often lose muscle mass despite adequate caloric intake. Pergolide medication, prescribed by your veterinarian, is the primary treatment for PPID.
Horses with gastric ulcers benefit from frequent small meals, ad lib hay access, and reduced grain intake. Lucerne hay has a clinically demonstrated buffering effect on gastric acid and is often recommended as part of an ulcer management program. Use our free Ulcer Risk Checker to assess your horse's risk.
