Carbohydrates in horse nutrition
Carbohydrates are the major source of energy for the horse. However, carbohydrates are a big family and include a great variety of components - from the simple sugars to the more complex starches and celluloses. Different carbohydrates are digested either enzymatically in the small intestine or fermented by intestinal microbes, mainly in the hind-gut.
Small intestinal digestion
In the small intestine, sugar and starch are enzymatically broken down into simple sugars and absorbed into the blood as glucose (blood sugar). This is then transported to the liver, muscles and other organs and used directly for energy or stored as glycogen or body fat. The level of blood glucose is strictly regulated by insulin. Most horses have few problems with the absorption and regulation of glucose, however there are some horses and ponies that are insulin resistant and have difficulties with the regulation of their blood glucose. For these horses, sugar and starch in the ration must be kept as low as possible.
In normal rations, it is mainly the starch from grains in compound feeds that can cause a problem. Barley and maize contain about 500 grams/kg, while oats contain about 350 grams/kg. In compound feeds, the starch content varies from about 140 grams/kg and up to 450 grams/kg. If your horse has problems tolerating too much starch in the ration, you should choose one of the low-starch feeds. For normal healthy horses, it is recommended to not give more than 0,4 kg cereal-based compound feeds per 100 kg body weight per meal. This means max 2 kg per meal for a 500 kg horse.
Fermentation in the hind-gut
The fibres, mainly cellulose and hemicellulose, are fermented by microbes in the caecum and colon. This leads to the production of volatile fatty acids, mainly acetic acid, propionic acid and butyric acid. These acids are absorbed and readily utilized for energy or stored as fat. Propionic acid can also be converted to glucose in the liver. Volatile fatty acids produced in the hind-gut do not lead to any problems for the horse and are readily absorbed and utilized. Therefore, forage and other fibrous feeds should make up as big a part of the horse’s ration as possible. This is also vital for normal fill and transport in the gut.
When using PC-Horse to compose your rations, you will always be able to see how much sugar, starch and fibre the ration contains. This allows you to adjust the ration and optimize it for each individual horse. In addition, you will also see the content and balance of the other nutrients required.
This article was originally written by Dr. Day Austbø.
Copyright: PC-Horse International - Norway 2017.
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