Sugars (glucose, fructose, and other sugars), classified as carbohydrates and more precisely as saccharides, have a sweet taste. Since sugar, derived from starch in cereals, serves plants as an energy store, it has high energy content and is easily digestible. The main sugar sources for our horses are grass and hay.
Sugar content depends on the age of the grass or the cutting time of the hay, and thus on the fiber content. The crude fiber content and the proportion of energy or easily digestible carbohydrates are inversely proportional, that is, if the crude fiber content is high, the energy content is low; if the energy content is high, the crude fiber content is correspondingly lower.
The later the cutting time of the hay, the more energy the plant consumes and the higher the crude fiber content and the lower the energy (sugar) content. If the sugar content in the horse's total ration is too high, or above its requirements, it can have different effects on the horse. It can lead to the horse's sugar balance being overloaded or to the digestive capacity of the small intestine being exceeded because of the quick passage time, so that the sugar cannot be completely digested in the small intestine.
The excess sugar then enters the large intestine, which can lead to a disturbance in the balance of bacteria, or intestinal flora. The result is an inefficiently working large intestine, which can lead to fecal water, diarrhea, and irritation of the mucous membranes, as well as ulcers and gas colic. Therefore it is very important to gradually introduce horses to grazing and possibly reduce the concentrated feed ration (if the horse gets concentrated feed) so that there is no surplus energy.
Hay should also contain sufficient structurally effective raw fiber so that the horse's structural needs are covered and the horse is sufficiently saturated. This is especially essential breeds with a low energy requirement, such as Icelandics, Haflingers, and Shetland ponies.