Delivering Energy to Horses

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Delivering Energy to Horses

Grains with seed coats, such as oats (seen here), tend to be somewhat lower in carbohydrates and higher in fiber than hull-less seeds.

Photo: The Horse Staff

While some horses might not need supplemental energy in their diet (think easy keepers), one of the most common reasons for feeding a horse concentrated carbs is to fuel his ability to work over and above his normal maintenance metabolism. He can store the energy from grains in long glucose chains called glycogen and call on these chains to power his performance.

During exercise the horse’s muscle fibers can tap into energy from muscle glycogen stores, from circulating blood glucose, or from stores in the liver. The longer the exercise interval and the more intense the exercise, the more glycogen gets used up. When strenuous exercise continues for some time, the horse’s muscle and liver glycogen stores can become seriously depleted, so maintaining carbohydrate availability is important, particularly for horses asked to do sustained work, such as endurance racing. Being asked to work hard with depleted glycogen stores hastens the onset of fatigue in these horses, though the effects of diminished glycogen stores on the performance of short-term, high-intensity athletes is less well understood.

The ability to replace depleted glycogen stores following exercise can be important for succeeding performance efforts, and some evidence suggests that the best time to do that is in the first few hours following an athletic effort. (Feeding both hay and grain post-exercise seems to do a better job of refilling glycogen stores than feeding hay alone.)

Delivering the Goods

Supplying your horse with energy-rich carbohydrates is as easy as running down to the feed store and picking up a bag of grain. Or is it?

All grains contain large amounts of carbohydrates and starches, but not all grains are equivalent. Here’s what they have in common: Grains are four to eight times as heavy as baled hay (per unit volume); they’re low in fiber and about 50% higher in dietary energy than average-to-good quality hay; and starch makes up 55% or more of their dry matter.

Grains with seed coats, such as oats, tend to be somewhat lower in carbohydrates and higher in fiber than hull-less seeds such as corn, which are very carbohydrate dense. On the whole, starch digestibility by the horse is high—researchers estimate that the average horse uses from 87% to 100% of the starch he’s given. And therein lies a problem: When a large grain meal hits the horse’s small intestine, some of the starch is digested and absorbed as simple sugars, as it’s meant to be, but the rest, instead of passing through the system undigested, is converted by the microflora in the cecum to volatile fatty acids and lactic acid. If the production of these acids is rapid enough (as can happen when a horse gets a large grain meal at one sitting—or when he breaks into the feed room and gorges), cecal acidosis can result—a condition that can trigger diarrhea, colic, and laminitis.

To reduce the risk of this reaction, it’s wise to follow the old horseman’s credo of “small meals often.” This gives the small intestine time to process the carbohydrates before the system moves everything along to the cecum. The more carbohydrates get in the small intestine, the less cecal acidosis. Because forage in the system can decrease the amount of grain processed in the small intestine, it’s best not to feed hay for an hour or more before feeding grain or for three or more hours afterward—though this rule is more important for high-performance horses routinely receiving large amounts of carbohydrates than for the average pleasure horse eating only a small amount of supplemental grain.

Other approaches that can help include giving preference to grains with fiber-rich hulls, such as oats, or choosing grains processed by grinding, rolling, flaking, or heat treatment to improve the digestibility of the starches.

About the Author

Karen Briggs

Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.

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