Low-NSC Horse Feeds: What Kind Does My Horse Need?

Q. My horse was recently diagnosed with a metabolic condition and now must consume a low-starch, low-sugar diet. I currently feed a regular performance feed, because he’s in moderate to hard work and not the easiest of keepers. I have been looking for a different feed and have found a number with words like “low-starch,” “lite,” “low-carb,” and “safe” in their name. Would one of these be appropriate for my horse?

A. It’s generally recommended that horses with conditions such as insulin resistance (IR), equine metabolic syndrome (EMS), and polysaccharide storage myopathy (PSSM) consume diets low in starch and sugar.

Most horse owners are familiar with the fact that traditional grains such as oats and corn contain high levels of starch (40 to 60%), as do some commercial performance feeds. It’s tempting to focus on the grain in the diet; however, don’t to forget about the forage in the ration. Selecting an appropriate commercial feed won’t have as much an effect in managing the condition if the forage in the diet provides far too much starch or sugar. Ideally, have your forage tested to ensure it’s low in starch and sugar; if you can’t have it tested, consider soaking to lower the sugar content.

Recommendations about starch and sugar amounts for such horses varies depending on who you ask and the specific condition being managed. For the EMS and IR horses, veterinarians and nutritionists often recommend that dietary non-structural carbohydrate (NSC) be below 12% on a dry-matter basis. NSC is calculated by adding the starch and water soluble carbohydrate (WSC) fractions of a feed together.

However, not all WSCs contribute to a blood glucose spike, because not all of it’s absorbed in to the blood stream from the small intestine. Some WSCs require microbial fermentation in the horse’s hindgut, so they don’t impact blood glucose in the same way. Ethanol soluble carbohydrate (ESC) captures monosaccharides and disaccharides that can raise blood glucose but far less than the microbial requiring sugars. Some argue that ESC combined with starch is what should be considered when feeding horses with metabolic conditions.

To make matters even more confusing, starch and ESC combined is sometimes erroneously referred to as NSC, when, as mentioned, NSC is starch plus WSC. When inquiring what a feed’s NSC value, always ask how the value provided was calculated.

Read Past the Feed Label

Are feeds with words such as low-starch, lite, low-carb, and safe appropriate for horses such as your own? Not necessarily. These words suggest that the amount of starch and or sugar in the feed is lower than in traditional cereal grain based feeds. This is likely true, but there’s no standard that defines the term “low-starch.” Feeds exist that use these terms and that are truly low in starch and ESC or starch and WSC and therefore safe to feed horses with conditions such as insulin resistance. However, some feeds using these terms still have a starch and sugar content around the low- to mid-20% range. These feeds are better thought of as having “controlled starch” rather than low-starch.

While some states have carbohydrate guidelines for use of terminology on feed labels these are rare and nationally it will be a long time before there is a generally accepted definition of what terms such as low-starch actually mean. Because of the lack of regulations surrounding these terms you as a buyer really need to look carefully at the feeds to determine whether they are truly appropriate for your horse.

One of my pet peeves is the term “low-carb” when it comes to horse feeds and diets. I often hear owners say that they need a no-carb or low-carb diet for their horse. A horse fed a no-carb diet would likely be dead or, at least, very unhealthy. It is important to understand that carbohydrates come in many forms. Cell wall components of feed ingredients and forages are made up of complex carbohydrates. Fiber is a carbohydrate. Without adequate levels of these forms of carbohydrate in the diet there would be very little for the horse’s hindgut bacteria to utilize.

It’s a specific type of carbohydrate we are trying to limit in these horses, not all forms of carbohydrate. In fact, horses eating 1.5% of their body weight as forage are consuming very high levels of carbohydrates.

While it sounds as though your horse needs extra calories, it’s important to remember that feeds in this category aren’t always low in calories. Many horses with conditions that require low starch and sugar are easy keepers and also need reduced calorie intakes. Feeds labeled lite, low-starch, and low-carb aimed at performance horses are not low in calories. Fat is often utilized as a calorie source along with fermentable fiber and these ingredients can provide significant calories.

Take-Home Message

The key to selecting feeds for horses with these conditions is to feed according to the horse’s condition and only feeding low-NSC performance feeds if the horse needs additional calories for weight gain or maintenance.