Starch found its way into horse feed with the use of cereals. Unlike roughage, starch is high in energy and low in crude fibre - it is a polysaccharide consisting of two glucose units and thus belongs to the non-structural carbohydrates, unlike cellulose or hemicellulose (crude fibre), for example. Since the horse's metabolism is not designed to utilise large amounts of starch-rich feed, the horse has only low amylase production and activity.

Amylase is an enzyme that is produced, for example, by us humans in the pancreas and in the salivary glands of the oral cavity and is responsible for the cleavage of polysaccharides. Due to the small amount of amylase, the horse is not a good "starch digester" and can reach its limits in this respect.

Digestion of starch

Unlike humans, the digestion of starch in horses does not take place in the oral cavity, but in the small intestine. If the horse's total ration is too rich in starch (and at the same time too low in raw fibre), various problems can occur.

On the one hand, the horse's structural needs are not sufficiently met, so that the horse chews too little, resulting in too little saliva being produced. The result is a drop in stomach pH, as there is not enough saliva to buffer the constantly forming stomach acid. The too low pH value leads to irritations and lesions of the stomach mucosa, up to and including stomach ulcers.

If the amount of starch is above the digestive capacity of the small intestine, the undigested starch goes into the large intestine where it is fermented by large intestine microbes (intestinal flora) into volatile fatty acids and lactic acid. As a result, the large intestine becomes over-acidic. Similar to the stomach, this damages the mucous membrane and can lead to intestinal ulcers. This impairs the absorption of nutrients in the large intestine and the horse, which is actually supplied with sufficient energy, loses weight.

The problem of too much starch in the gut

Too much starch in the large intestine can also lead to a shift in the intestinal flora. This means that starch-fermenting bacteria (and also fungi) multiply. These displace the cellulose-fermenting bacteria, which form toxins as a result of their death, which is also promoted by the low pH value. These toxins in turn trigger colic and laminitis.

It is therefore important that if starch is used, which is mainly found in cereals and maize in horse feed it is fed in frequent, small rations that do not exceed the requirement in order not to unnecessarily burden the horse's digestive tract.