All mammals, including horses, are not able to digest fibre at all, and yet fibre is crucially important as a source of nutrition for horses. So how is it that fibre is such an important component of horses’ diets if they are unable to digest it?
The answer is that horses and all other mammals rely on billions upon billions of health-giving beneficial microflora (tiny single-celled micro-organisms) that live and breed in their hindgut to ferment the cellulose, hemicellulose and pectin which are components of fibre.
Only lignin (the component of fibre that makes some grasses and plants tough and stalky) is not able to be fermented by gut microflora. Therefore has no nutritional value, but it still has a role in toning the muscles surrounding the intestines and helping to bulk up the ingesta moving through and ‘sweeping out’ contaminants like sand from horses’ GI tracts.
Horse nutritionists teach that one of the best ways to prevent or treat sand in the gut in horses is to feed ad lib grass hay.