Oats for horses

There is a misconception among many horse owners that oats shouldn’t be fed to horses because they are likely to make them ‘hot’ and ‘fizzy’. In most cases, this simply isn’t the case, although there are always some exceptions.

In This Article:
The BENEFITS of feeding OATS
Why is PHOSPHORUS important in horses’ diets
Why OATS are healthy for horses
Why BETA-GLUCAN is healthy for horses
The CONCERNS when feeding OATS
Are OATS safe for horses with Equine Metabolic Syndrome?
Why some horses DON’T do well on OATS


The BENEFITS of feeding OATS

Oats are a very good source of quick-release energy (predominantly in the form of starch, but also some sugar) for horses in work. Oats are a good source of the mineral phosphorus, and also provide protein (about 13%) and fibre, plus B vitamins. Horses ideally require a ratio of calcium to phosphorus of 1.5 - 2 parts calcium to one part phosphorus.


Phosphorus (as well as calcium and magnesium) is very important for healthy bones, teeth, joints and hooves. Phosphorus is also important for a healthy metabolism (eg: for protein synthesis and for the utilization of carbohydrates and fats). Phosphorus is also an electrolyte, so is important in the diet of all horses, but especially those horses in work who suffer extra electrolyte losses through sweat.


Oats contain a highly digestible form of starch that doesn’t require heat treatment or processing. Therefore oats can be fed whole and unprocessed to horses. Oats are the only grain fed to horses that contain starch that is easily digested raw; all other types of grain (eg barley, corn, wheat, rice) fed to horses should be heat – treated: eg boiled, slow-cooked, steamed, steam-rolled, extruded or micronized) to improve the digestibility of the starch and to help to avoid hindgut issues. The digestibility of the starch in raw oats is around 90% while the digestibility of the starch in corn, wheat and barley is around 35% (until it is heat-treated and then it rises to around 90%, the same as raw oats).

Oats are the grain which are highest in fibre and lowest in sugar and starch of all the cereal grains fed to horses, so they are least likely to cause insulin spikes and blood sugar fluctuations, as well as hindgut and/or behavioural issues.


Oats are a good source of beta-glucan, which is a polysaccharide that has numerous health benefits for horses. Beta-glucan boosts beneficial gut microflora, lowers insulin resistance and reduces blood sugar fluctuations and slows the rate of passage of hard feed through the GI system allowing greater enzymatic digestion of starch in the small intestine, thus reducing the risk of hindgut acidosis.

Oats are highly palatable for horses, so are a good choice of feed for enticing fussy horses to eat, or for horses being introduced to hard feed after previously living only on pasture and/or hay.


Oats are high in phosphorus and low in calcium (they are around 0.3% phosphorus and only 0.07% calcium), which can be a major issue if the diet doesn’t provide sufficient calcium and/or if the horse is grazing on high oxalate pasture (eg Kikuyu, Setaria or Buffel) which causes calcium deficiency.

Excess phosphorus inhibits the absorption of calcium. (As stated earlier, ideally horses should be provided with a ratio of 1.5 – 2 parts calcium to one part phosphorus in the diet. According to the National Research Council Nutrient Requirements for Horses document (based on scientific evidence from around the world) a 500kg horse that is not in work requires 14grams of phosphorus per day and 20grams of calcium.


Oats contain around 13% protein, but the protein in oats is low in the essential amino acid lysine which is an essential nutrient for all horses, especially pregnant and lactating mares and growing youngsters, and horses in work. Therefore the protein is not considered to be high-quality protein. This is true for ALL cereal grains, not just oats.

This drawback can be rectified by feeding lucerne and/or lupins, both of which are all good sources of lysine, with the oats. This will boost the lysine content of the diet, and improve the overall amino acid profile of the meal.


Even though oats are the grain lowest in sugar and starch, at around 45 to 50% starch they are still far too high in starch for horses on a low sugar and starch diet, eg insulin resistant horses, horses prone to laminitis, those with disorders like Cushings or PSSM etc, as well as many horses who are prone to ulcers, colic and hindgut issues.

Unless horses are in heavy work they don’t really require grain in the diet at all (according to many equine nutritionists) because a diet high in digestible fibre from feed sources like pasture, hay, haylage, hay cubes, beet pulp, legumes and legume hulls etc provides more than enough digestible energy (in a slow-release sustained form). These high fibre feeds are also healthier for horses because they boost beneficial gut microflora and discourage the overgrowth of pathogenic microflora,  and therefore boost overall health and immunity.


1.Sensitivity or allergy to the protein in oats (although this is more likely to occur with barley or wheat due to the gluten they contain – gluten is a known common allergen).

2.The horse has trouble chewing the hard seed coats (hulls) of the oats. In this case, soaking, steaming or cooking the oats for a few hours before feeding them out, or feeding crushed or steam-rolled oats is a better option than feeding whole oats.

3.Volume of oats fed. Why does the volume matter? Horses produce amylase enzymes in their pancreas, which are required to digest starch in the small intestine. Compared to other mammals horses only produce relatively small amounts of amylase (because their natural diet is usually low in starch). Individual horses also vary in the amount of amylase they produce. Horses that produce more amylase then others tolerate larger amounts of oats (and other grain) better than horses that produce smaller amounts of amylase.

If a particular horse is fed oats (or other grain) and becomes colicky or uncomfortable, scours or develops ulcers and/or hindgut issues, or becomes irritable and difficult to handle or ride then chances are that this particular horse only produces small amounts of amylase and isn’t tolerating the starch in the diet well (assuming the issues aren’t due to parasites, infection, injury or some other source). If this is the case then reducing the amount of oats (or other grain) fed, or eliminating them from the diet altogether, should resolve the issue. Or alternatively,  horse supplements with digestive enzymes (containing amylase) can be used, which will improve small intestinal enzymatic digestion of the oats (or other grain). If a horse is fed more oats (or other grain) then can be digested by enzymatic action in the small intestine then the grain will arrive in the hindgut undigested. There it will be rapidly fermented by acid-producing microflora, which results in the lowering of the pH of the hindgut, which can lead to gut dysbiosis (an imbalance between beneficial and pathogenic gut microflora), damage to the hindgut lining, pain, inflammation, ulceration, scours, colic, irritable and excitable behaviour, and even severe illness in the form of laminitis.

Written by Elizabeth Funnell
Equine Nutrition Educator

Sub-editor Bryan Meggitt (BMedSc. PGCrtMedSc.)
Senior Scientist and Co-founder of CEN Horse Nutrition


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