Quick Answer: However, Gustafson's analysis found that higher NDF had very little effect on sugar levels and no meaningful effect on starch or fructans.
For years, many horse owners have been advised to feed coarse, stemmy hay to horses prone to laminitis and insulin dysregulation.
The assumption is simple: more fibre must mean less sugar.
But research by equine nutritionist Kathleen Gustafson suggests it isn't that straightforward.
As hay matures, its Neutral Detergent Fibre (NDF) increases, making the forage coarser and more stemmy.
However, Gustafson's analysis found that higher NDF had very little effect on sugar levels and no meaningful effect on starch or fructans.
In other words, a stemmy hay is not automatically a low-sugar hay.
What did consistently decline as hay matured was nutritional value. Protein, digestible energy and important minerals including calcium, magnesium, copper and zinc all fell as NDF increased.
For horses with insulin dysregulation, the main concern is the sugar and starch that stimulate insulin release, rather than the amount of structural fibre itself.
The takeaway?
Don't judge hay by appearance alone.
A coarse hay may still contain significant sugars, while a softer, greener hay may be perfectly suitable.
The only way to know what your forage contains is to test it.
Best wishes,
The Forageplus Team