Feeding Starch – finding the right levels for your horse

De Morris warmblood gelding

In an ideal world, horses should be fed as they have evolved to ie on a free choice high fibre diet.  After all, wild horses are quite capable of galloping for considerable distances without any hard feed.  So if you’re feeding starch – the right levels are crucial for good digestive health.  However, how much does your performance horse really need? What other sources of energy can be used if your horse is starch intolerant?

Energy sources for horses

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

Feeding Starch – the right levels – Grains 

Traditionally, grains have always been considered the main source of energy for hard working horses. Starch is a carbohydrate found mostly in grains in the form of polysaccharides composed of many linked glucose molecules. Grains are mostly digested in the small intestine where they’re broken down and absorbed as glucose (simple sugar). Some starches, however, are resistant to small intestine digestion and are fermented in the large intestine.  A typical analysis doesn’t differentiate between the two types.

The Glycaemic Response

Low starch content in a feed generally means little glucose will be absorbed in the small intestine.  This is known as a low glycaemic response. It’s 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 glycaemic response.

However, horses fed on only a high roughage diet need to be able to produce glucose for energy from a non-carbohydrate source. This is because glucose precursors such as starch will only be present in minimal quantities.  Therefore, roughage fed horses  become adapted to producing glucose from either VFA’s (volatile fatty acids), fats or proteins. It’s ideal for endurance horses as mobilizing fat reserves delays the onset of fatigue.

Starchy feeds – the instant energy hit

Compared to fatty acids, glucose (or glycogen in its stored form) is aerobically metabolized nearly twice as fast generating ATP for muscle contraction. Starchy feeds also provide more instant energy for horses performing high intensity exercise. Unfortunately, the horse is limited in how much starch it can process, and large quantities poses an immediate digestive challenge.  This can result in metabolic disorders such as equine metabolic syndrome or gastric ulcer syndrome

Safe limits of feeding starch

So what are the safe limits when feeding starch to performance horses? The table below is a useful standard guide as to how much can safely be fed to prevent digestive issues.

To avoid starch overload,rapid fermention in the h/gut   <2g/kg BW/meal

To avoid risk of gastric ulcer syndrome



For metabolic disorders such as IR, Cushings, laminitis etc



From this table you can see how important it is to weigh feed to ensure safe starch intake limits aren’t exceeded.

Feeding Oats – fast food for horses

The mere mention of feeding oats sends the average horse owner screaming for the hills.  Yet in bygone days it was the standard grain of choice for hard working horses. Nowadays, your average leisure horse  hardly needs hard feeding, never mind being fed oats.

Many commercial hard feed products boast an ‘oat-free’ formula yet include barley and maize.   Due to their higher oil content, these two grains are actually higher in energy.  Furthermore, they need some form of processing eg micronising or extruding for better pre-caecal digestion.

A Versatile Option

By contrast, oats are a versatile feedstuff and can be fed whole, crushed or  husk-less (naked oats).  Naked oats have an improved oil and nutrient level content.  Additionally, when fed naked oats, the horse becomes less dependent on starch-rich concentrates.  This is because the overall feeding levels can be reduced. All good so far!

Did You Know?

Below we list several facts about whole oats you may not have been aware of:-

  • They’re less energy dense than corn (maize) or barley
  • Contain less starch and greater protein content than corn or barley
  • Have high prececal starch digestibility even before breakdown. 90% compared to 30-35% for corn and barley.  Oat starch is more readily digested than corn starch in the small intestine.  Therefore, oats fed in appropriate amounts will produce less starch to the small intestine.
  • Higher in the essential amino acid lysine than corn or barley.
  • Contain a high proportion of mucilaginous substances.
  • Oats contain a high proportion of husks (50%) so more fibre than corn or barley.
  • Higher fat content than corn or barley.
  • Ideal to chew taking into account the horse’s dentition
  • Horses produce copious amount of saliva when eating them which facilitates easy breakdown.
  • Excellent palatability, without them having to be smothered in molasses.

To Feed or not to Feed? Hmmm….

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.  This avoids upsetting the delicate microbes and enzymatic process of the hindgut.

3) Old horses with poor dentition may find whole oats hard to chew.  Soaking them in boiling water before feeding will help to soften them up.

4) Know your horse’s weight. 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 for quick release energy.  Adding a Fibregenix balancer to the hard fed horse, be it straight grains or concentrate mixes, means the unique combination of digestive supplements will assist in the horse’s capacity to digest its starch.  This in turn will help maintain fore and hindgut health and will enable less starch and more fibre to be fed.  Such a strategy will always ultimately lead to a happier horse and better performance.

Reviewed and updated Feb 2021

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