The Carbohydrate Fructan:

Use Caution with Spring Grazing

During the sunny, longer, spring days as well as early fall, horse owners need to be attentive to their horses with grazing times along with evening temperatures. This is particularly true for those with a history of metabolic syndromes, laminitis, founder, insulin resistant, PSSM, and Cushing’s. During the spring, grazing cool-season grasses that are high in fructans/sugars can adversely influence the gut’s bacteria. That influence can alter the gut’s pH and subsequently create an inflammatory response that may cause a first-class belly ache (colic) that could lead to laminitis and/or founder.

Sugar and fructan concentrations in spring grasses are higher in mid/late afternoons and early evenings. Fructans are a short chain of the simple sugar fructose. However, this fructose compound is structurally unlike the fructose in fruit sugars, honey and sugar cane. Fructans are a storage form of this plant sugar that are not digested by foregut enzymes but are fermented (digested by bacteria) in the hindgut.

These sugars that have accumulated in the plant during the day from photosynthesis will be used for growth. Subsequently, the next morning the sugar/fructan levels will usually be lower which suggests the best time for grazing is early morning. However, if evening temperatures are low (<40°F), growth is reduced, and the sugars not used for growth will be stored as complex fructans. If the evenings are warm, the plant will use the sugars which is why early morning grazing is considered the best time. Horse owners have always been encouraged to introduce horses to pasture slowly but they also need to consider the time of day along with a gradual length of grazing time. A management option of feeding hay prior to and after turn-out is a good practice for influencing/regulating digestively the high fructan spring grass. Overgrazed pastures are also an issue. Horses grazing closer to the ground are consuming younger plants, less stem, thus less complex fiber, thus a plant with higher fructans and sugars.

The amount of fructans in grass will vary with growth stage of the plant. One also needs to consider the complex carbohydrates (cellulose, hemicellulose) in the plant relative to plant maturity. More mature plants have more stem, thereby less sugars/fructans.

How do you know how much fructans are in the forage?

WSC (Water Soluble Carbohydrate) is the laboratory analysis that represents fructan and sugar content. ESC (Ethanol Soluble Carbohydrate) represents the simple sugars. The difference between WSC and ESC is an estimate of the fructans; emphasis is on “estimate” as it’s not an absolute value. There is some question on the accuracy of fructan levels with the WSC analysis; nevertheless, the two lab analyses do provide a tool for estimating fructans.

How useful is that information with estimating fructan consumption?

This is a good question since there is not any data to establish what a safe level of consumption of fructans in spring grass forage is. Also, sampling grasses for analysis would represent levels only for that sample. Plant stage of growth, time of day, weather preceding sampling will influence the results of the analysis and thus not represent an overview of fructans consumed during the course of the season. Subsequently, grazing management is the best option.

What carbohydrate data is useful in specifically addressing the different metabolic syndromes?

The laboratory analyses %starch, %ESC and %WSC. An overview of these lab assessments is provided below. Note NSC is not included. NSC is defined by the NRC-Nutrient Requirements for Horses as %starch + %WSC – a number combining starch and WSC that represents starch, sugars, fructans, and some other oligosaccharides. Another concern is the inconsistences in published NSC values that are not defined in accordance with NRC. This misrepresentation of NSC has included %starch + %ESC, %ESC + %WSC, just %WSC and NFC (a mathematical calculation). This confusion not only exists for horse owners but also in the veterinarian community. NSC is not useful, and this nutritionist does not use NSC to evaluate carbohydrate consumption to address the different metabolic syndromes.

Are all horses at risk consuming spring grass?

No, but equids that are fat, ponies, minis and horses with known metabolic syndromes appear more susceptible. There has been some speculation that horses with higher energy demands such as growth, lactation, intense workers may be less susceptible; however, there is no data nor science to support this assumption.

An Overview of Carbohydrate Assessment

% Starch

This represents starches that consist of numerous glucoses hooked together and are broken down by small intestine enzymes; relative to diet, some starch may escape enzymatic digestion, thus expose the starch to microbial fermentation.


(Ethanol Soluble Carbohydrates)

This represents sugars digested in the small intestine; sugar is the carbohydrate that produces a true glycemic (blood sugar) response.


(Water Soluble Carbohydrates)

This represents simple sugars, fructans and some other oligosaccharides. Fructan is a short chain of sugars (primarily the sugar fructose) connected like the sugars in fiber; they are NOT broken down by foregut enzymes but broken down by hindgut microbially fermentation. Fructans are prevalent in forages, particularly immature growing forages and are at higher levels in afternoon grasses, which is why there is caution with horses grazing in the afternoon/early evening on spring grass.

For more detailed information, all of the Starch, ESC and WSC analyses for Integrity horse feed products can be found here.