Fructan content does matter! Don't use just ESC + starch!!

Meadow grass ryegrass pasture and hay

Fructan content of grass, hay and haylage should be considered when assessing suitability of forages for horses and ponies affected by laminitis and metabolic disturbances.

It’s been proposed that fructan content of forages can be ignored for horses and ponies affected by equine metabolic syndrome (EMS), laminitis, insulin dysregulation (ID), obesity and PPID.

There seems to be two reasons for this, both of which are flawed:

  1. “Fructan is not broken down by digestive enzymes so doesn’t affect the insulin response”. This is flawed because fructan is partially broken down by bacterial fermentation in the foregut (stomach and small intestine) and there is no good evidence that fructan does not affect insulin response
  2. “Fructan ingestion from pasture would never be high enough to causes laminitis from hindgut disturbance”. This is flawed because there is no knowledge of the amount of fructan that could disturb hindgut function enough to contribute towards metabolic problems (without making the horse ill and causing classic gut disturbance-laminitis)

It is possible that fructan does contribute to insulin response in some individual horses or ponies (see the technical note for references). There is no good evidence that it does not affect insulin response. Therefore, assumptions should not be made.

Furthermore, there is no evidence that pasture-associated laminitis – or that caused by hay high in sugar and fructan – is caused solely by insulin dysregulation. It may be due to a combination of insulin dysregulation and hindgut disturbance from excess intake of fructan.

The research to date does not prove either way whether or not high fructan intake could be associated with laminitis. Much of the research has been undertaken using purified inulin, a type of fructan which is different to that found in grass. Research should be interpreted with great care and its important to bear in mind that results only apply directly to the situation of the particular trial and may not relate directly to the real-life situation.

In future it may well be possible to be more accurate in how to feed horses and ponies affected by laminitis and metabolic disturbances. For the time being, however, using NSC is the accepted method of ensuring the diet is suitable for a horse or pony with ID. NSC covers sugar, starch AND fructan. 

In conclusion, it is too early to conclude that grass fructan does not contribute to equine pasture-associated laminitis (includes that caused by hay/haylage intake) and other metabolic disturbances. It is both foolhardy and detrimental to horse health and welfare to ignore forage fructan content for laminitis predisposed or metabolically challenged animals until further research increases our knowledge and understanding.


  • Fructan is a grass plant storage carbohydrate that is part of the water-soluble carbohydrate (WSC) fraction of the plant (along with sugar); digested only via bacterial fermentation and there is little knowledge of how much is digested where in the gut
  • Sugar is also found in grass – generally in smaller quantities than fructan - and is sometimes described via its analytical description ethanol soluble carbs (ESC); digested thoroughly in the small intestine according to research to date
  • Non-structural carbohydrates (NSC) cover fructan, sugar and starch and is the current accepted fraction in the total diet, to help control insulin dysregulation and associated laminitis in the horse. Note that starch levels in UK grass are consistent and generally <2% (although can range up to 4% in seeded grass), unlike WSC and ESC levels which can vary widely – hence why WSC is sometimes used instead of NSC
  • Pasture associated laminitis; that caused at least partially by insulin dysregulation and with a different disease process compared to gut disturbance laminitis
  • Gut disturbance laminitis: that caused by overload of starch or fructan, caused at least partially by excess fermentation in the hindgut leading to a cascade of microbiome disturbance, acidosis and leaky gut wall
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