In an ideal world, horses would be fed as they have evolved to be fed ie on a high fibre diet only.  After all, a wild horse is quite capable of galloping for considerable distances when required without having to stop for a quick top up of hard feed.  So how much starch does your performance horse really need and what other sources of energy can be used if your horse is starch intolerant?

Energy can be supplied to the horse in different forms such as fat, carbohydrate or protein and is also available from body reserves of glycogen stored in the muscles and liver or from fat distributed throughout the horse’s body.

Starch in the diet

Starch is a carbohydrate found mainly in grains in the form of polysaccharides composed of many linked glucose molecules; grains are mostly digested in the small intestine where they are broken down and absorbed as glucose (simple sugar). Some starches are resistant to small intestine digestion and are fermented in the large intestine; a typical analysis doesn’t differentiate between the two types.  However, low starch content in a feed generally means little glucose will be absorbed in the small intestine (this is known as low glycemic response). This is good for horses that can’t handle large blood sugar changes (i.e. insulin-resistant horses). High starch content in a feed is the opposite and generally means a high glycemic response.


Traditionally, grains have always been considered as a main source of energy for hard working horses, however a horse on a high roughage diet with no grains needs to be able to produce glucose for energy from a non-carbohydrate source since glucose precursors such as starch will only be present in minimal quantities.  This is when roughage fed horses therefore become adapted to producing glucose from either VFA’s (volatile fatty acids), fats or proteins –  ideal for horses undertaking endurance work  as the horse that can adapt to mobilizing fat reserves delays the onset of fatigue.  Compared to fatty acids, however, glucose (or glycogen in its stored form) is aerobically metabolized nearly twice as fast to generate ATP for muscle contraction. Although starchy feeds may provide more instant energy, which is deemed essential for horses performing high intensity exercise, the limitations of the horse to be able to process starch in large quantities poses an immediate challenge to the health of the digestive system and can create metabolic disorders.

So what would be the standards for safe limits of starch fed to performance horses?

There are several conditions associated with excess dietary starch intake, eg gastric ulcer syndrome or equine metabolic syndrome, and the following table is a useful standardised guide as to the amounts of starch that should be fed where there are sensitivities prevailing.

 % starch in your hard feedIDEAL TARGET
To avoid starch overload,rapid fermention in the h/gut50-65% for sweet feeds, 45-75% for straight grains<2g/kg BW/meal

To avoid risk of gastric ulcer syndrome



For metabolic disorders such as IR, Cushings, laminitis etc



This table highlights the importance of weighing feed to ensure safe starch intake limits are not exceeded. Whilst on the subject, an overview of one particular starch source that is much maligned is due consideration– OATS.  Many hard feed products boast an ‘oat-free’ formula yet include barley and maize; these hard grains are not only higher in energy due to their higher oil content, but also need some form of processing to enable better pre-caecal digestion, usually micronizing or extrusion whereas oats can be fed whole, crushed or even husk-less, (also known as naked oats).  Naked oats have an improved oil and nutrient level content which means the horse can become less dependent on starch-rich concentrates when fed naked oats because the overall feeding levels can be reduced.   Below is a list of facts about whole oats that many people are not aware of:-

1) Oats are less energy dense than corn (maize) or barley

2) Oats contain less starch and greater protein content than corn or barley

3) Oats have high prececal starch digestibility even before breakdown – 90% compared to 30-35% for corn and barley, and oat starch is more readily digested than corn starch in the small intestine.  This means that oats fed in appropriate amounts will produce less starch to the small intestine.

4) Oats are higher in the essential amino acid lysine than corn or barley.

5) Oats contain a high proportion of mucilaginous substances.

6) Oats contain a high proportion of husks so more fibre than corn or barley.

7) Oats contain a higher fat content than corn or barley.

8) Oats are ideal to chew taking into account the horse’s dentition

9) Oats have very high palatability without them having to be smothered in molasses.

10) Horses produce copious amount of saliva when eating them which facilitates easy breakdown.

However, there are also things to be aware of for the safe feeding of this grain product:

1) Consider honestly whether your horse is in the sort of work that requires a grain energy source – be it oats, or any other hard feed.

2) Always introduce oats to the diet (as with any new feed) slowly over 10-14 days to avoid upsetting the delicate microbes and enzymatic process of the hindgut.

3) Old horses with poor dentition may find whole oats hard to chew so they can be soaked in boiling water before feeding.

4) Know your horse’s weight and never feed more than 1-2g of oats per kg of bodyweight in any one meal to avoid undigested starch leaking into the hindgut.

5)  As per the table above, avoid all grains where there are compromised digestive systems.

To summarise – at Fibregenix we will always promote a primarily fibre enriched diet for horses and ponies, particularly those at maintenance or in lower levels of work,  however we do appreciate there are times when a horse in particularly hard work may need a starch source in his diet for quick release energy.  The benefit however of adding a Fibregenix balancer to the hard fed horse, be it straight grains or concentrate mixes, is that the unique combination of digestive supplements will assist in the horse’s capacity to digest its starch, maintain fore and hindgut health and additionally will enable less starch and more fibre to be fed.  Such a strategy will always ultimately lead to a happier horse and better performance.