Carbohydrates in Horse Diets

Additional "carbs" in a horse's diet are sometimes necessary and sometimes not.
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Carbohydrates can come in various forms in a horse's diet.

Feeding “carbohydrates” to horses has been frowned on in recent years for its contribution to gastric ulcer disease, colic, laminitis and behavior problems. However, nearly three-quarters of plant matter is made up of carbohydrates. These “carbs” come in two forms: a) structural carbohydrates, which are cell wall components of cellulose that are fermented by intestinal bacteria to produce energy; and b) non-structural carbohydrates (NSC), which break down into simple sugars and can cause metabolic problems.

In the small intestines, carbohydrates are digested into simple sugars. In the large intestines and cecum, carbohydrates are fermented into volatile fatty acids that are efficiently used to produce energy. It is recommended to feed hay before offering a concentrate meal to slow the rate of intake of concentrate.

If excess carbs are ingested, as in grain products, an overflow of sugars and starches into the large intestine can wreak havoc with intestinal flora through increased acidity of the bowel contents. This kills off important digestive bacteria and allows other bacteria to overgrow. It also affects the integrity of the bowel lining to result in leaky gut syndrome, where substances and pathogens normally confined within the intestinal tract cross cell membranes and are picked up in the bloodstream to circulate throughout the body and even into the brain to elicit behavioral abnormalities. 

Too much sugar in a horse’s diet can lead to metabolic problems such as obesity, insulin dysfunction and a risk of laminitis.

Idle horses don’t usually need added carbohydrates (as NSC) in the diet. Working horses might need more NSC components in their diets to provide for energy needs of exercise. This should be provided in the form of small grain meals spread throughout the day to avoid starch overload and spillover into the large intestines. Better yet, fat is a useful substitute for calories instead of using grain carbohydrates.