Common Horse Feeding Mistakes to Avoid

Quick Q&A

Question: What are the most dangerous feeding mistakes I can make with my horse? Answer: The most critical errors include feeding excessive grain (which can trigger laminitis or colic), making abrupt changes to the diet (disrupting the hindgut microbiome), and failing to provide constant access to forage and clean water. Each of these can lead to severe, life-threatening conditions.

Introduction

Equine nutrition is a cornerstone of preventive veterinary medicine. Yet despite decades of research and clinical guidelines, common feeding mistakes remain a leading cause of preventable illness in horses worldwide. From the pleasure pony to the elite sport horse, dietary errors contribute to colic, laminitis, equine metabolic syndrome (EMS), gastric ulcers, and behavioural issues. This article examines the three most prevalent feeding errors as identified by the American Association of Equine Practitioners (AAEP) and the Merck Veterinary Manual: overfeeding grain, sudden diet changes, and neglecting forage and water. We also address additional pitfalls such as inappropriate feeding schedules, toxic plants, and ignoring individual metabolic conditions.

By understanding the science behind these mistakes, horse owners, veterinarians, and managers can implement evidence-based feeding programmes that optimise health and performance. Whether you are in North America, Europe, Australia, or Canada, the principles of safe equine feeding remain remarkably consistent.

Mistake 1: Feeding Too Much Grain (Concentrates)

The Physiological Consequences of Excessive Starch

Horses evolved as continuous grazers on fibrous grasses. Their digestive system, particularly the hindgut (caecum and colon), is designed to ferment fibre slowly. When a horse consumes a large, starch-rich meal of grain (e.g., oats, corn, barley, or commercial mixes), the small intestine can become overwhelmed. Undigested starch spills into the hindgut, where it is rapidly fermented by resident bacteria. This leads to:

• Lactic acidosis: a sudden drop in hindgut pH, favouring lactic-acid producing bacteria and killing beneficial fibre-fermenting microbes.
• Colic: gas distention, pain, and potentially torsion due to altered fermentation.
• Laminitis: systemic inflammation triggered by hindgut acidosis and release of vasoactive substances (e.g., endotoxins). The AAEP identifies laminitis as a direct emergency requiring immediate veterinary intervention.

Clinical Signs of Excessive Grain Feeding

• Restlessness, pawing, looking at the flank (early colic)
• Diarrhoea or loose manure
• Increased heart rate and respiratory effort (laminitis)
• Reluctance to move or shifting weight (founder)
• Obesity and cresty neck (chronic overfeeding in insulin-dysregulated horses)

Safe Grain Feeding Guidelines

According to the Kentucky Equine Research (KER) and the Merck Veterinary Manual, the following principles should guide grain use:

1. Limit grain to no more than 0.5% of body weight per meal (e.g., 2.5 kg (5.5 lb) for a 500 kg horse) and no more than 2.5 kg per meal unless divided.
2. Feed grain in multiple small meals (at least two, ideally three or more) rather than one large feeding.
3. Use low-starch, high-fat alternatives (e.g., beet pulp, rice bran, vegetable oil) for horses with high energy needs or metabolic disorders.
4. Introduce grain gradually over 7–10 days when adding to the diet (see Mistake 2).

Regional Considerations

• In Australia and parts of Europe, oaten hay and chaff are common, but their starch content varies by harvest. Always test for non-structural carbohydrate (NSC) levels in feeds if your horse is prone to laminitis.
• In North America, sweet feeds (molasses-based) are popular but can spike insulin. The AAEP advises caution with these feeds in horses with equine metabolic syndrome.

Mistake 2: Making Sudden Feeding Changes

The Hindgut Microbiome

The equine large intestine harbours a complex microbial community that requires days to weeks to adapt to new forage or concentrates. Abrupt diet changes, whether in hay type, grain brand, or pasture access, can disrupt this ecosystem, leading to dysbiosis and digestive upset.

Clinical Consequences of Abrupt Changes

• Colic: The most commonly cited trigger for sporadic colic in horses is a sudden change in diet (Merck Veterinary Manual).
• Diarrhoea or constipation due to microbial imbalance.
• Laminitis: A sudden increase in lush pasture grass high in fructans can cause rapid hindgut fermentation and laminitis in susceptible horses.
• Fasting followed by refeeding (e.g., after transport or illness) must be managed with extreme care to avoid refeeding syndrome.

How to Change Diets Safely

The AAEP and the Horse (thehorse.com) recommend:

1. Transition over 7–14 days: Replace 25% of the old feed with new feed every 3–4 days.
2. Maintain a consistent forage base: Hay is the foundation; change hay gradually by mixing old and new bales over 10 days.
3. For pasture turnout: Confine horses to a dry lot for several hours per day initially, allowing gradual adaptation to lush grass.
4. Monitor manure consistency: If it becomes loose or odd-smelling, slow the transition.

Special Populations

• Young horses (weanlings) are particularly sensitive. Weaning should include a gradual reduction of the dam's milk alongside introduction of solid feed over 2–3 weeks.
• Senior horses: Their reduced digestive efficiency necessitates longer transition periods (up to 3 weeks) when introducing new complete feeds or hay cubes.

Mistake 3: Ignoring Forage and Water

The Vital Role of Forage

Forage should constitute at least 1.5% to 2% of the horse’s body weight per day on a dry-matter basis. For a 500 kg horse, that equates to 7.5–10 kg (16.5–22 lb) of hay or pasture dry matter. Yet many owners mistakenly reduce hay when grain is fed, or restrict hay to prevent obesity, leading to:

• Gastric ulcers: The equine stomach continuously secretes acid. Without a constant supply of saliva (from chewing) and a fibre mat, acid splashes the non-glandular squamous mucosa, causing ulcers. The AAEP estimates that 60–90% of performance horses have gastric ulcers.
• Stereotypic behaviours: Wood chewing, cribbing, and weaving often stem from chronic hunger and lack of forage.
• Colic and impaction: Low forage intake reduces gut motility and increases risk of impaction colic, especially in winter when water intake may also drop.

Water: The Overlooked Nutrient

A horse at rest requires 5–10 gallons (20–40 litres) of water daily, increasing dramatically with heat, work, or lactation. Dehydration:

• Impairs appetite and digestion.
• Increases risk of impaction colic.
• Reduces blood flow to the hoof laminae, potentially predisposing to laminitis.
• Affects thermoregulation and performance.

Common Forage and Water Mistakes

• Feeding dusty or mouldy hay: Causes respiratory issues and possible mycotoxin ingestion (e.g., Aspergillus). Always soak hay for horses with respiratory conditions.
• Allowing 24/7 free-choice hay in obese horses: Without management, leads to excessive calorie intake. Use slow-feed hay nets or controlled turnout.
• Providing insufficient water in winter: Heaters or insulated buckets are essential in cold climates. Check daily that water is not frozen.
• Assuming pasture alone meets nutritional needs: Most pastures require rotational grazing and soil testing to ensure adequate minerals and avoid excess NSCs.

Practical Solutions

• Use a forage-first approach: Calculate hay or pasture needs based on body weight and condition score.
• Provide salt and electrolyte supplements to encourage drinking, especially in hot weather.
• Consider soaking hay for horses with metabolic conditions (to reduce NSCs) or for those prone to choke.

Additional Common Feeding Mistakes

Mistake 4: Inappropriate Feeding Schedules

Horses are trickle feeders; being left without feed for more than 4–6 hours is stressful. Feeding only twice daily without forage in between is a risk factor for ulcers and colic. The ideal schedule includes:

• Multiple small forage meals (e.g., 4–5 times daily for stalled horses).
• Timed grain feedings at the same times each day → horses anticipate meals and their digestive enzymes are primed.

Mistake 5: Ignoring Individual Variation

Horses differ by breed, age, workload, and metabolic status. A “one-size-fits-all” feeding programme is inappropriate.

• Equine metabolic syndrome (EMS): Requires low-NSC (<10–12%) diets, strict forage restriction, and no grain.
• Pituitary pars intermedia dysfunction (PPID): Older horses often need specialised feeds with reduced soluble carbohydrates.
• Growing horses: Need balanced calcium and phosphorus for bone development; overfeeding grain can cause physitis.
• Performance horses: Require careful meal timing (grain 2–3 hours before work) to avoid colic during exercise.

Mistake 6: Toxic Plants and Contaminated Feed

Common toxic plants include ragwort (Senecio), red maple leaves, and acorns. Feed contaminated with blister beetles (in alfalfa hay), ergot alkaloids (in grasses), or aflatoxins (in stored grains) can cause severe disease. Always source feed from reputable suppliers and inspect hay for weeds and blister beetles.

Mistake 7: Over-reliance on Supplements

Many horses receive unnecessary supplements. Before adding anything, assess the diet: balancing major minerals (calcium, phosphorus, salt) is more critical than a handful of “herbal tonics”. The KER advises a hay analysis to guide supplementation, especially for horses in training or breeding.

Clinical Guidelines and Regional Differences

US and Canada (AVMA/AAEP/CVMA)

• Routine dental care is essential for proper feed utilisation; annual examination by a veterinary dentist or certified equine dentist is recommended.
• Vaccination protocols for Clostridium and Salmonella may reduce risk of infectious colic, but good feeding hygiene remains paramount.

Europe (FVE/EFSA)

• The European Commission regulates feed additives and labelling. Owners should check that concentrates comply with EU feed hygiene regulations.
• Pasture management includes concern for equine grass sickness (EGS) in Northern Europe and the UK; feeding hay of known provenance is part of risk reduction.

Australia (AVA/DAFF)

• No quarantined pests (e.g., Pteridium esculentum (bracken fern) toxicity) and tick paralysis (Ixodes holocyclus) in coastal regions. Feeding must account for these regional toxicities.
• Lush pasture can lead to laminitis in genetically susceptible ponies; careful grazing management is critical.

Conclusion

Avoiding the three cardinal feeding errors of overgrazing (too much grain), abrupt dietary changes, and neglecting forage and water is the foundation of equine health. By understanding the equine digestive physiology and adhering to evidence-based feeding protocols, owners can dramatically reduce the incidence of colic, laminitis, gastric ulcers, and other nutritionally mediated diseases. Always consult with a veterinarian or equine nutritionist before making major changes to your horse’s diet, especially if the horse has a history of metabolic issues or digestive upset.

Remember: the horse’s gut is the engine of its health. Feed it with consistency, patience, and respect for its evolutionary design.

References

[1] American Association of Equine Practitioners (AAEP). “Feeding Horses: Guidelines for Health and Performance.” aaep.org. Accessed 2025. [2] Merck Veterinary Manual. “Feeding and Nutrition of Horses.” merckvetmanual.com. Accessed 2025. [3] Kentucky Equine Research (KER). “Nutritional Mistakes That Harm Horses.” ker.com. Accessed 2025. [4] The Horse (thehorse.com). “Common Feeding Mistakes.” 2023. [5] AVMA (American Veterinary Medical Association). “Laminitis in Horses.” avma.org. Accessed 2025. [6] Veterinary Clinics of North America: Equine Practice – Colic issue (2022). [7] CVMA (Canadian Veterinary Medical Association). “Equine Feeding Safety.” canadianveterinarians.net. [8] AVA (Australian Veterinary Association). “Feeding Horses in Australia.” ava.com.au. [9] EFSA (European Food Safety Authority). “Feed Hygiene and Equine Health.” efsa.europa.eu. [10] Geor, R.J., Harris, P.A., & Coenen, M. (Eds.). Equine Applied and Clinical Nutrition. Saunders Elsevier, 2013.