How to Feed Grains Safely to Horses

Grains can be a useful part of a horse’s diet, especially for horses in harder work, poor doers, growing horses, lactating mares, or horses that need more energy than pasture and hay alone can provide. However, grains need to be fed with care. Horses are designed to eat small amounts of forage over long periods, not large grain meals. When grain is overfed, fed too quickly, or fed in a form that is difficult to digest, it can create serious digestive problems.

The key to feeding grains safely is understanding where they should be digested.

Foregut vs hindgut digestion

The horse’s digestive system can be thought of in two main sections: the foregut and the hindgut. The foregut includes the stomach and small intestine. This is where starch from cereal grains should ideally be broken down and absorbed. Cereal grains such as oats, barley and corn are high in starch, and the horse uses enzymes in the foregut to break starch down into sugars that can be absorbed and used for energy.

The hindgut includes the caecum and colon. This is where fibre from pasture and hay is fermented by microbes. These microbes are extremely important for the horse’s health. They help turn fibre into volatile fatty acids, which are a major energy source for the horse.

Problems occur when too much starch escapes digestion in the small intestine and moves into the hindgut. The hindgut is not designed to handle large amounts of grain starch. When excess starch reaches the hindgut, microbes ferment it rapidly, producing acids that lower hindgut pH. This can disrupt the normal microbial balance, irritate the gut lining, and increase the risk of digestive upset, colic, laminitis and founder.

Why large grain meals are risky

The horse has a relatively small stomach compared with many other livestock species. The stomach makes up only about 10% of the horse’s total digestive tract volume, while the caecum and colon make up around 50%. Large meals can move through the stomach and small intestine faster, which increases the chance that undigested starch will reach the hindgut.

For this reason, grain should be fed in small, controlled meals. A commonly used guideline is to feed no more than 0.5% of the horse’s bodyweight in cereal grain at one meal. For a 500 kg horse, that is no more than about 2.5 kg of grain at once, although many horses will need far less than this.

It is also important to feed by weight, not by scoop. One scoop of oats does not weigh the same as one scoop of corn or pellets. Some grains are much denser than others, so using volume alone can easily lead to overfeeding.

Are all grains digested the same way?

No. Different grains vary in how easily their starch is digested in the small intestine.

Oats are generally considered the safest and most digestible cereal grain for horses. They have a higher fibre content than most other grains and are bulkier, meaning they provide less energy per scoop than denser grains. Whole oats are often well chewed and digested by horses, although rolling or crimping can help older horses or horses with dental issues.

Barley is more energy dense than oats and has a harder grain structure. It is usually rolled, steam flaked, micronised or otherwise processed before feeding. Whole barley is not ideal because the horse may not digest it efficiently.

Corn is very energy dense and high in starch. It can be useful in performance diets but is easy to overfeed. Whole corn may pass through the digestive tract partly undigested, while finely ground corn can move too quickly and may increase the risk of hindgut fermentation if fed in high-concentrate diets. Steam rolling, flaking, micronising or extrusion can improve digestibility.

Wheat is not commonly fed as a straight grain to horses. It is dense, high in starch and generally best used only in carefully formulated mixes or as by-products such as bran or middlings, where appropriate. Wheat and wheat middlings should not be fed in heavy, unbalanced amounts.

Research comparing grains has found that oats had much higher pre-caecal starch digestibility than barley and maize. In one study, oats had pre-caecal starch digestibility of 0.949, compared with 0.705 for barley and 0.663 for maize. This helps explain why oats are often considered a more forgiving grain, while barley and corn benefit more from proper processing.

Why cooking, flaking and micronising matter

Processing grains helps make starch more available for digestion in the small intestine. Methods such as steam flaking, micronising, extrusion, rolling and crimping break or alter the grain structure so digestive enzymes can access the starch more easily.

For oats, minimal processing is often enough. A light crimp or roll may be useful, especially for horses that do not chew well, but whole oats are usually better digested than whole barley or whole corn.

For barley and corn, processing is more important. Heat processing, such as steam flaking, micronising or extrusion, can gelatinise starch and make it easier for the horse to digest before it reaches the hindgut. Research on cereal processing in horses has identified grain type, grain processing and individual digestive ability as major factors influencing how much starch is digested in the small intestine.

However, more processed does not always mean safer. Finely ground grain can be dusty, may be eaten quickly, and can pass rapidly through the digestive tract. Coarse processing or heat processing is generally preferable to finely ground meals for horses.

Practical rules for feeding grain safely

Start with forage first. Hay and pasture should be the foundation of the diet. Good forage supports gut health, chewing, saliva production and more natural feeding behaviour.

Only add grain when there is a genuine need for extra energy. Many horses in light work do not need much grain at all and may do better on forage, a balancer, minerals and salt.

Introduce grain gradually. Any new grain or hard feed should be introduced over 7–14 days so the digestive system and gut microbes can adapt.

Keep grain meals small. If a horse needs a higher amount of concentrate, split it into two or more meals rather than feeding one large meal.

Choose the right form. Oats may be fed whole or lightly processed, while barley and corn are safer and more digestible when properly processed.

Avoid sudden changes. A sudden increase in grain, a new feed, or accidental access to a feed bin can overload the digestive system. If a horse breaks into grain or eats a large amount unexpectedly, contact a vet promptly.

Store grain properly. Feed should be clean, dry and free from mould, dust, insects and contamination. Mouldy grain should never be fed.

Balance the whole diet. Grain adds energy but may not provide the correct balance of protein, minerals and vitamins. Commercial feeds, balancers or supplements may be needed depending on the horse’s forage, workload and condition.

The safest approach

Grain is not “bad”, but it must be respected. The safest grain-feeding program is one that uses the smallest amount needed, in the most digestible form, alongside plenty of forage. For many horses, especially good doers or horses in light work, less grain is often better.

When grain is needed, feed it by weight, keep meals small, choose properly processed grains, and make changes gradually. This helps support foregut digestion, reduces the risk of starch overflow into the hindgut, and keeps the horse’s digestive system healthier and more stable.

If you are unsure which grain or feed is right for your horse, speak with your vet, equine nutritionist, or the team at Oakford Stockfeeds for guidance based on your horse’s workload, body condition, age and current diet.