15/07/2026
Why can laminitic horses eat hay but not grass?
This confuses people because hay and grass are both forage. So if a horse canât have grass, people often assume they canât have hay either. But the issue isnât whether itâs called grass or hay. The issue is how much sugar and starch is in it.
Grass and hay can vary massively depending on the species, the season, the weather, the time of day, and the stage of growth when itâs eaten or cut. Grass makes sugar during the day through photosynthesis. On a normal growing day, sugar builds through the day and is usually higher later in the afternoon. Overnight, if conditions are warm enough for growth, the plant uses some of that sugar. Thatâs why early morning is often talked about as the lower sugar grazing time.
But that only applies if the plant has actually been able to use the sugar overnight. If weâve had frost, drought stress, or temperatures cold enough that growth slows or stops, that sugar can stay trapped in the plant. So the grass can look short, sad and harmless, but still be far too high in sugar for a laminitic or insulin resistant horse.
Short stressed grass, fresh growth after sunny weather, frosty grass, seed heads, rye, clover and improved pasture can all be a problem for horses who are sensitive to sugar and starch.
Hay is like a snapshot of the grass at the time it was cut. Its sugar and starch levels depend on the species, the weather, the time of day, and the stage of growth. Ryegrass cut on an overcast morning with no seed heads may test very differently from ryegrass cut on a sunny afternoon with seed heads.
Thatâs why we test hay where we can. For laminitic, PPID, EMS or insulin resistant horses, weâre generally looking for hay under 10% ESC plus starch. Rhodes and lucerne often test low, but the name of the hay still doesnât tell us everything. Testing is how we know whatâs actually in that batch.
If we donât have a test, soaking hay can help reduce some of the soluble sugars, but it doesnât make every hay safe and it doesnât fix high starch. Itâs a useful tool, not a guarantee.
This is the nuance. Itâs not as simple as grass bad, hay good. Itâs also not true that grass and hay are exactly the same, so neither can be fed. It depends whatâs actually in it.
For a laminitic or metabolic horse, the safest base is suitable low sugar forage. That might be tested low sugar grass hay, soaked hay while youâre waiting on a test, or soaked low sugar hay pellets or cubes if they canât chew hay.
The goal is not to remove fibre. The goal is to remove unsafe sugar and starch while still keeping safe fibre going through the gut.
