If you’ve just been indoctrinated into the world of metabolic disease, you’ve likely heard about the dangers of sugar in your horse’s diet. However, not all sugars are bad, says Jyme Nichols, PhD, Director of Nutrition for Bluebonnet Feeds, in Ardmore, Oklahoma.

“Some simple carbohydrates are essential for life functions,” said Nichols during her presentation at the 2023 EquiSummit, a virtual equine nutrition conference held Sept. 5-6. “The brain, for example, needs sugar in the form of glucose to function.”

Where is the sugar in your horse’s diet?

Horses must consume forage (hay and grass) to survive, and all hays and grasses contain sugar. “There is no such thing as a zero-sugar diet for horses,” said Nichols. Rather than trying to eliminate all sugar from a horse’s diet, owners should limit the amount of sugar metabolic horses consume.

As a general rule, diets for horses with metabolic conditions should have a nonstructural carbohydrate (NSC) content of 12% or less on a dry matter basis (equivalent to 10% as fed, which includes moisture).

NSCs are the water-soluble sugars and starches in plant cells, in contrast to the structural carbohydrates that make up plant cell walls. “Almost every food that a horse eats will have NSCs, except if you’re offering a pure vitamin/mineral complex or fat,” said Nichols. Anything with fiber will have some NSC content, she added.

To achieve that maximum 12% NSC, horse owners must understand the source of sugar in a horse’s diet.

“Sugar hides in green grass,” said Nichols. “Growing grass undergoes photosynthesis, which produces sugar that plants use for energy to grow. Grass can easily contain 17% NSC.”

Sugars are particularly adept at hiding in cool-season grass hays such as orchard-grass, timothy, and bluegrass. These grasses have more NSCs in the form of fructans than warm-season hays, which pose a greater risk of laminitis. “If you’re feeding a metabolic horse, this difference is important,” emphasized Nichols.

When possible, Nichols recommends leaning on warm-season grasses (e.g., Bermuda) or even a legume like alfalfa if you want a hay lower in NSCs. “Warm-season hays just don’t store as much sugar as cool-season hay,” she said.

It’s still best, however, to have your hay tested for NSC content.

How can owners reduce the NSC content in their horse’s diet?

Soaking your horse’s hay for 30-60 minutes, then tossing out the water before feeding, is an effective way to reduce its NSC content and make it safer for your horse to eat, said Nichols. “For example, a 30-minute soak reduces NSC by 2.3 points.” However, if the hay has a very high starting NSC level, owners might not be able to reduce it to a safe enough level through soaking.  

Hay-only diets almost never provide enough trace minerals, vitamins, or amino acids to meet a horse’s needs. Therefore, horses on forage-only diets often need a supplement or ration balancer to ensure they are consuming enough vitamins and minerals.

“This is another hiding spot for sugar,” said Nichols. “When looking for a supplement, select something that is low enough in NSC to complement the forage component.”

If your hay has a very low NSC content, you might be able to choose from a wider range of supplements than if your hay has a high NSC level, in which case you’ll need to choose a condensed vitamin/mineral product, she added.

Cereal grains often have an NSC content of 50-70%, which is a dangerous level for horses with metabolic problems. “Say goodbye to textured sweet feeds if you have a metabolic horse,” Nichols said.

Even treats can have dangerous sugar levels. “I strongly recommend you avoid using them,” said Nichols. “They can pack a surprising amount of sugar, even apples, carrots, and oat bars.”

Despite these “rules,” Nichols said metabolic horses must be managed on an individual basis. “Metabolic horses that cannot be turned out on pasture may need a small dry-lot area, have hay specially sourced and tested, be denied sweet feeds, and offered either a ration balancer or even just a straight vitamin/mineral mix,” she summarized.

Work with your veterinarian and an equine nutritionist to develop a diet that is healthy for your individual horse so you can manage their metabolic status.