Understanding Carbohydrates in Equine NutritionBy Martin W. Adams, PhD, PAS - Equine Nutritionist for Southern States · March 22, 2017
When determining low-carbohydrate diets for horses, we need to look at sugar and starch, Non-Structural Carbohydrates (NSC), levels in equine feeds. It’s important to include forages (hay and pasture), as well as ingredients that make up concentrate feeds for horses, such as oats, corn, barley, beet pulp and soybean meal, when calculating total carbohydrates. If large amounts of sugar and starch are consumed, they can pass through the stomach and small intestine of the horse in an undigested state.
When large amounts of sugar, starch or fructans are present in the hindgut, they are rapidly fermented. Excessive fermentation in the hindgut results in large amounts of lactic acid that can lower the pH to the point at which most of the bacteria are destroyed. These bacteria then break apart and release toxins that are absorbed into the bloodstream. These toxins are believed to cause laminitis in the horse.
A low carbohydrate feeding program will provide your horse with feedstuffs below 20% NSC daily. The lowest NSC values are for soybean hulls, beet pulp, alfalfa and the feedstuffs with highest NSC values are corn, barley and oats. It is obvious that grain-based horse feeds will contain significantly higher NSC values than feeds based on beet pulp, soybean hulls and alfalfa meal.
Additionally, determine the NSC content of your pasture or hay by having a sample analyzed. One surprising finding concerning NSC levels of various hays was that alfalfa hay and alfalfa cubes had lower values than grass hay, so alfalfa hay may become the first choice for a low NSC diet. The most prudent feeding management to reduce NSC levels in the diet would be to eliminate or reduce grazing. This can be accomplished by moving the horse to a barren lot for activity only or the use of a grazing muzzle to lower or eliminate pasture consumption.