Nutritional Requirements for Growing Horses: What They Need at Each Stage

Getting nutrition right during a horse's growth years is one of the most important things you can do for their long-term health and soundness. Nutritional mistakes made during development can lead to developmental orthopaedic disease (DOD), poor bone density, stunted growth, or excessive growth rates that stress immature joints.

The challenge? A growing horse's nutritional requirements change significantly from birth through to maturity. What a nursing foal needs is vastly different from what a yearling requires, and a two-year-old entering early training has yet another set of demands.

This guide walks you through each stage of growth, explaining exactly what your young horse needs and why.

Why Growing Horses Have Unique Nutritional Needs

Unlike mature horses that simply need to maintain their body condition, growing horses are actively building bone, muscle, tendons, ligaments, and organ systems. This construction work demands higher concentrations of energy, protein, minerals, and vitamins relative to body weight than an adult horse requires.

Horses do roughly 90% of their growing in the first two years of life. A Thoroughbred foal born at around 55 kg can reach 450–500 kg at maturity — an extraordinary transformation that depends entirely on the building blocks provided through nutrition.

The key principles for feeding growing horses are:

• Steady, consistent growth is always better than rapid spurts followed by periods of restriction
• Mineral balance matters as much as mineral quantity — ratios of calcium to phosphorus, zinc to copper, and other mineral interactions are critical
• Protein quality (amino acid profile) is more important than crude protein percentage
• Forage should remain the foundation of the diet at every stage

Stage 1: The Nursing Foal (Birth to 4–6 Months)

The First Few Days

Colostrum — the mare's first milk — is the foal's lifeline in the initial 12–24 hours. It provides essential antibodies (immunoglobulins) that the foal cannot produce on its own. While not strictly a "nutritional" requirement in the traditional sense, without adequate colostrum intake, the foal's immune system is severely compromised.

A healthy foal should stand and nurse within 1–2 hours of birth. If a foal fails to nurse within 4 hours, veterinary intervention is needed.

Nutritional Needs of the Nursing Foal

For the first 2–3 months, mare's milk provides virtually everything the foal needs. Mare's milk is relatively low in fat (about 1.5–2%) compared to other species but high in lactose, providing readily available energy for the foal's rapid early growth.

During this stage, foals grow at their fastest rate — gaining roughly 1–1.5 kg per day in the first month for light breeds, and up to 2 kg per day for draught breeds.

By 2–3 months of age, mare's milk alone begins to fall short of the foal's increasing demands. You'll notice foals starting to nibble at grass and the mare's feed. This is natural and should be encouraged.

Introducing Creep Feed

A creep feed is a specially formulated concentrate offered to foals in a feeder the mare cannot access. Introducing creep feed from around 2–3 months of age helps:

• Bridge the nutritional gap as milk production plateaus
• Prepare the foal's digestive system for weaning
• Provide essential trace minerals (particularly copper and zinc) that mare's milk is often deficient in

A good creep feed should contain:

• 14–16% crude protein with quality amino acids, especially lysine (the first limiting amino acid in horses)
• At least 0.8% calcium and 0.5% phosphorus, maintaining a Ca:P ratio of at least 1.5:1
• Adequate copper (25–50 mg/kg) and zinc (100–120 mg/kg) for cartilage and bone development
• Controlled starch and sugar levels to avoid excessive growth rates

Start with small amounts — around 0.5 kg per day — and gradually increase as the foal approaches weaning.

Stage 2: The Weanling (4–6 Months to 12 Months)

The Weaning Transition

Weaning is one of the most stressful events in a young horse's life. The nutritional goal during this period is to maintain steady growth without the energy and protein previously supplied by mare's milk.

Poorly managed weaning nutrition is one of the most common triggers for developmental orthopaedic disease. Sudden changes in energy intake — either too much or too little — can cause growth disturbances that affect cartilage and bone development.

What Weanlings Need

A weanling's diet should provide:

• Energy: Enough to support a growth rate of approximately 0.7–1.0 kg per day for a horse expected to mature at 500 kg. This typically requires a diet with a digestible energy content of around 12–13 MJ DE per kg of total dry matter intake.
• Protein: 14–16% crude protein in the total diet, with a lysine content of at least 0.65% of the total diet. Soybean meal is one of the best supplementary protein sources for young horses due to its excellent amino acid profile.
• Calcium: 35–40 g per day
• Phosphorus: 20–22 g per day
• Copper: 30–40 mg per kg of total diet dry matter
• Zinc: 100–120 mg per kg of total diet dry matter
• Selenium: 0.1–0.3 mg per kg of total diet dry matter (be cautious — selenium toxicity occurs at relatively low levels)

Forage for Weanlings

Forage should make up at least 1–1.5% of the weanling's body weight daily. Good-quality grass hay or a grass-legume mix works well. Pure lucerne (alfalfa) hay can be used but may provide excessive protein and calcium, so it's best mixed with grass hay.

Good pasture is ideal for weanlings, providing not only nutrition but also the opportunity for free exercise, which is essential for proper bone and joint development.

Common Mistakes at This Stage

• Overfeeding concentrates to make weanlings look impressive — this drives excessive growth rates and increases DOD risk
• Ignoring mineral balance — providing a generic supplement without checking the actual mineral content of forage and pasture
• Restricting feed after weaning in an attempt to control growth, which can cause compensatory growth spurts later

Stage 3: The Yearling (12 to 24 Months)

Changing Growth Patterns

By the yearling stage, the rate of growth has slowed considerably, but the horse is still gaining significant bone density, muscle mass, and body size. A yearling expected to mature at 500 kg will typically weigh around 300–350 kg and is gaining approximately 0.5–0.7 kg per day.

The nutritional demands per kilogram of body weight are lower than for a weanling, but the total daily requirements increase as the horse gets bigger.

Nutritional Requirements for Yearlings

• Energy: Moderate — overfeeding energy is the most common mistake at this stage. Yearlings being prepared for sales are particularly at risk of being over-conditioned.
• Protein: 12–14% crude protein in the total diet, with continued emphasis on lysine and methionine (the two most limiting amino acids).
• Minerals: Calcium and phosphorus requirements are slightly lower relative to body weight but still significantly higher than for mature horses. Aim for 28–36 g calcium and 16–20 g phosphorus daily.
• Forage: Should now make up the majority of the diet — at least 1.5% of body weight, ideally more.

The Sale Prep Trap

Yearlings being prepared for sales are often fed excessive concentrates to achieve a "well-grown" appearance. This practice is associated with increased incidence of osteochondritis dissecans (OCD) and other developmental joint problems. A yearling that looks slightly lean but has strong, correct limbs and good bone is in much better shape long-term than one that is overly fleshed.

If you're feeding a yearling, focus on quality over quantity. A well-balanced concentrate fed at moderate levels alongside excellent forage will produce a much healthier horse than a high-energy ration pushed to extremes.

Stage 4: The Two-Year-Old (24 to 36 Months)

Approaching Maturity

By two years of age, most of the skeletal framework is in place, though bones continue to increase in density and the growth plates in some bones — particularly the vertebrae and pelvis — don't close until age 4–6. Growth rate has slowed to around 0.2–0.4 kg per day.

Many two-year-olds are entering some level of training, which adds a new nutritional dimension.

Nutritional Requirements

• Energy: Requirements increase if the horse is in work. A two-year-old in light training needs energy comparable to a mature horse in moderate work, PLUS a small additional allowance for continued growth.
• Protein: 11–13% crude protein. The amino acid quality remains important for continued muscle development.
• Calcium and phosphorus: Still higher than for a fully mature horse. Aim for 24–30 g calcium and 14–17 g phosphorus daily.
• B vitamins and vitamin E: Become increasingly important if the horse is in training and may be stabled for significant periods (reducing access to fresh pasture).

Balancing Growth and Work

The challenge with two-year-olds in training is balancing adequate nutrition for both growth and athletic demand without overloading the digestive system with concentrates. Key strategies include:

• Feed little and often — never more than 2 kg of concentrate per meal
• Use high-quality fibre sources like beet pulp or soy hulls to boost energy without excess starch
• Maintain forage intake — even horses in training should receive at least 1.5% of body weight in forage daily
• Supplement electrolytes if the horse is sweating regularly during training

Critical Minerals for All Growing Horses

Certain minerals deserve special attention throughout the entire growth period:

Calcium and Phosphorus

The Ca:P ratio should always be between 1.5:1 and 2:1 in the total diet. An inverted ratio (more phosphorus than calcium) can cause serious bone disorders. Many cereal grains are high in phosphorus and low in calcium, so grain-heavy diets without calcium supplementation are dangerous for growing horses.

Copper and Zinc

These trace minerals are essential for cartilage and bone development. Copper deficiency is strongly linked to osteochondrosis and other developmental joint diseases. Many forages and pastures are low in copper, and high iron levels (common in many soils) can interfere with copper absorption.

A good guideline is to provide copper and zinc at a ratio of approximately 1:3 to 1:4 (copper to zinc).

Manganese

Often overlooked, manganese plays a role in cartilage formation and bone development. Growing horses need approximately 40 mg per kg of diet dry matter.

Monitoring Growth and Adjusting the Diet

Regular monitoring is essential. Use a weight tape every 2–4 weeks and track growth rates. Body condition scoring should be done monthly — growing horses should maintain a condition score of 5–6 on the 1–9 Henneke scale.

If growth seems too rapid, reduce concentrate intake gradually rather than making sudden cuts. If growth seems too slow, first check for health issues (parasites, dental problems) before increasing feed.

One of the best things you can do is take an analytical approach to your young horse's diet. Rather than guessing whether your foal, weanling, or yearling is receiving the right balance of nutrients, consider analysing your horse's diet to identify any gaps or excesses before they cause problems.

Feeding Tips for All Growing Horses

• Always ensure access to clean, fresh water — growing horses have higher water requirements relative to their size
• Provide a quality salt block or loose salt — sodium and chloride are essential and often deficient in forage-based diets
• Allow as much turnout as possible — free exercise promotes stronger bones and healthier joints
• Make all dietary changes gradually over 7–14 days to protect gut health
• Deworm strategically based on faecal egg counts — parasite burdens can severely undermine nutrition
• Work with your vet and nutritionist to develop a feeding plan tailored to your horse's breed, expected mature size, and individual growth pattern

Final Thoughts

Feeding growing horses well isn't about giving them the most expensive feed or the largest quantities. It's about providing the right balance of nutrients at each stage of development to support steady, healthy growth. The foundation is always good-quality forage, supplemented with a well-formulated concentrate that provides the protein quality and mineral balance that forage alone cannot deliver.

The investment you make in proper nutrition during your horse's first three years pays dividends for the rest of their life — in soundness, athletic ability, and overall health. Take the time to get it right, and your young horse will thank you with years of strong, sound performance.