Dietary fibre comprises the structural parts of plants which cannot be digested by intestinal enzymes. It includes in part, cellulose, hemicelluloses, pectin, lignin, indigestible protein, gums, waxes, and ash. Some parts of fibre such as cellulose may be digestible by microbial activity which in the horse occurs principally in the hind gut.
There are some other terms used to describe different parts of the total dietary fibre. These include Crude Fibre which is principally cellulose and lignin, and other terms like NDF (Neutral Detergent Fibre) for cell wall material and ADF Acid Detergent Fibre which refer to the laboratory techniques used to assess these different fibre fractions.
Fibre is an essential part of the horses diet and acts as a counterbalance to the non fibre carbohydrates like starch and sugars (NSC) to maintain healthy digestive and gut function. When dietary fibre intake is low horses will seek it out by chewing wood or eating bedding etc. to boost intake. The manure is a good indicator of dietary fibre adequacy – low fibre diets are typically characterized by small, hard dark coloured manure balls as opposed to the larger, greenish soft moist manure balls seen when fibre is plentiful.