If you’ve ever owned a horse with laminitis or metabolic issues, you’ve probably heard: “avoid starch at all costs.”
And while it’s true that excess starch can cause serious problems, it’s not as simple as “starch = bad.”
The real question is: what role does starch play, and when does it actually belong in a horse’s diet?
🌾 What Starch Does in the Body
Starch is a carbohydrate — a chain of glucose molecules mainly found in grains such as oats, barley, and corn.
In the small intestine, enzymes break starch down into glucose, which triggers an insulin response and provides a rapid energy source.
This glucose can be used immediately for energy or stored in the muscles and liver as glycogen which is used as a short-term energy reserve.
That process is only useful for horses in high-intensity or sustained workloads, such as:
- Racehorses
- Eventers or endurance horses
- Elite showjumpers
These horses benefit from moderate starch intake to replenish glycogen stores and delay fatigue.
But for the average performance, pleasure, or spelling horse, that same starch load is unnecessary and can cause more harm than good.
⚠️ When Starch Becomes a Problem
If starch intake exceeds what the small intestine can process, the overflow moves into the hindgut.
There, it’s fermented by lactic acid–producing microbes, dropping the pH and disrupting the microbial balance.
This cascade contributes to:
- Hindgut acidosis
- Laminitis
- Colic risk
- Behavioural changes linked to gut discomfort
That’s why laminitic, EMS, PPID, or ulcer-prone horses need diets that keep starch and sugar to an absolute minimum.
Where owners can then become stuck, is how "low starch" is low enough? Some horses can tolerate 15% - 22% starch but this quickly becomes a slippery slope and a 'matter of time' before hindgut acidosis will impact performance. A safe rule of thumb for horses with insulin sensitivity, ulcers, tying up or other issues - stick to less than 12% starch.
🌿 The Real Gut Hero: Fermentable Fibre
Where starch can cause trouble, fibre does the opposite.
Unlike starch, fibre isn’t broken down in the small intestine. It travels to the hindgut, where beneficial microbes ferment it — producing short-chain fatty acids (SCFAs) like butyrate and acetate.
SCFAs are powerful natural molecules that:
- Maintain a stable gut pH
- Strengthen the gut barrier
- Reduce inflammation
- Support calmness and recovery
Feeds rich in fermentable fibre - like beet pulp, soybean hulls, and lupin hulls - help nourish these beneficial microbes and create lasting gut health from within.
⚖️ It’s About the Right Type of Energy
| Energy Source | Digested In | Example Feeds | Best For | Key Risk |
|---|---|---|---|---|
| Starch (non-structural carbohydrate) | Small intestine | Oats, corn, barley | High-intensity work (race, endurance, eventing) | Insulin spikes, laminitis risk |
| Fibre (structural carbohydrate) | Hindgut (fermented) | Hay, beet pulp, soy/lupin hulls | All horses, especially metabolic or ulcer-prone | None — essential for gut health |
🧠 The Takeaway
- Starch isn’t the enemy, but it’s a fuel that needs context.
- For most horses, energy should come from fibre fermentation, not starch digestion.
- Reserve moderate starch feeding for horses in truly demanding work who require rapid glycogen replenishment.
- For everyone else, fibre-rich, low-starch diets support calmer energy, better gut integrity, and fewer metabolic risks.
- Learn what level of starch your horse can safely tolerate as every horse is individual and can respond to different feeds, differently. "Low starch" claims from feed manufacturers should be clarified by how much starch - some horses can tolerate 15% - 22% starch but this quickly becomes a slippery slope and a 'matter of time' before hindgut acidosis will impact performance. A safe rule of thumb for horses with insulin sensitivity, ulcers, tying up or other issues - stick to less than 12% starch.
By understanding how different carbohydrate types behave, you can feed smarter — supporting energy, gut health, and long-term soundness.