New Method of Counting Carbs

A new carbohydrate analysis method developed for the National Aeronautics and Space Administration (NASA) might be able to help researchers answer some specific questions about equine forages. Until now, it has been difficult for forage researchers to define exactly how much of several kinds of carbohydrates are present in forages. However, this new analysis method, which was developed by the USDA's Agricultural Research Service Forage and Range Research Laboratory at Utah State University for analyzing NASA samples of space-grown wheat, allows separation of simple sugars and fructans.

Carbohydrate Types in Forages

To understand the significance of this new method, first we must understand the basics of what carbohydrates are in forages and how they are currently evaluated. Structural, sometimes called insoluble, carbohydrates make up rigid plant components like the stems. It's the soluble carbohydrates, which serve as the plant's energy reserves, that can wreak havoc when susceptible horses eat large amounts.

These soluble carbohydrates are further divided into simple sugars (simple sugars like glucose and fructose, plus disaccharides) and fructans. The two types of carbohydrates are digested differently in the horse's body, but until now were not effectively analyzed separately. "Analytical methods pull out both at the same time," explained Kathryn Watts of Rocky Mountain Research and Consulting, a leading equine forage researcher.

Why is it important to separate different sugar types? Some researchers think that fructans, which are thought to impart more cold and possibly drought tolerance to plants and have been used to reliably cause laminitis in experiments, are most problematic in horses that aren't considered "laminitis-prone" or hyperinsulinemic. In these horses, the proposed mechanism of fructan causing laminitis is rapid fermentation of a high-fructan meal in the large intestine, since fructans are not digested in the stomach or small intestine. The rapid fermentation alters the bacterial population of the large intestine, killing off some bacteria that then release toxins. These toxins are absorbed from the intestine into the bloodstream, where they travel to different parts of the body, including the feet--where they cause laminitis.

But since fructans don't induce a glycemic response (rise of blood sugar following a meal), they aren't as dangerous to overweight, often hyperinsulinemic or Cushingoid horses as the simple sugars. These horses' blood sugar fluctuates more than normal horses' in response to sugar intake--this is the basis of the disease. High-sugar diets stimulate extreme changes in blood sugar and insulin, and although this has not been proven to cause laminitis attacks, it has been highly correlated with an increased risk. By differentiating between the two fractions of carbohydrates, perhaps the cause-effect relationships can be better clarified. (For more information on Cushing's/metabolic syndromes, see the Cushing's Disease topic at

"Chromatography is the best (method for analyzing forage carbohydrates)," said Jerry Chatterton, PhD, Research Leader of the Forage and Range Research Laboratory and leader of the team who developed the new testing method. "But that requires a lot of standards (for calibration) and expensive equipment (around $40,000)." The new method uses the same equipment currently used for enzyme digestion of forages, but uses  purified enzymes for more targeted breakdown and analysis of particular carbohydrate types.

 "This new technique allows us to look at all the fractions, now all we need is an epidemiological study to say which kinds of horses founder in what conditions," said Watts. "The horse industry doesn't know a lot about forages; there's much more knowledge in the cattle industry. Hay A can have twice as much carbohydrates as Hay B, and they look the same! When you double a horse's sugar intake when he has a metabolic problem, it's a big issue."

New Method

"It (the new testing method) doesn't really have a name yet; it's too new to have a name," said Chatterton. "We've used enzymes for a lot of years (30 or so) to analyze carbohydrates, but we've been using crude enzymes. The majority of their activity was what we wanted, but there were other enzymes in there that we didn't know what they did, so we've gone to a method that uses four purified enzymes. It's not that no one's used these enzymes before; what's unique is the way we've put them together and are able to come up with the different components.

"We've been working on it all summer, not full time, but we've tried a lot of things," he continued. "It's just taken a couple of months to work out the details."

This method involves using several enzymes one at a time, including amylase, maltase, and amyloglucosidase to pull out the non-structural carbohydrates other than fructans, then treating the sample with fructanase to quantify the fructans separately.

"We haven't done NASA's real samples yet, but that was what precipitated us using this more involved method," Chatterton explained. "We weren't comfortable using our current methods on those samples; they're once-in-a-lifetime-type samples (grown in space, currently stored in freezers awaiting testing). ARS researchers in Wisconsin are doing the cell wall analysis. NASA is interested in how plant cell walls and carbohydrates accumulate in space; one consideration is that because light intensity is low and there is no gravity, plant materials may have very different carbohydrate compositions than plants grown on Earth."

The new method will be more expensive than current analyses because the purified enzymes are more expensive, he said. Consumable supplies used in the analyses cost about $2.00 per sample, but these types of analyses are labor-intensive and will likely not be cheap, he added.

"We feel very confident that (this method) is something that gives an accurate estimate of carbohydrate content in these forages," he said. "Nothing is perfect; they're as good as the enzymes you use. Some of them are thermal stable--they’re stable at much higher temperatures (95°C). Most enzymes are inactivated above 35-40°C. It allows you to use less enzyme and less time."

Watts said that several hundred samples from a 2002 forage trial were retested using this method, and, "The total NSC (non-structural carbohydrate) content was very, very similar, so that would lend itself to validation." Previously the samples had been tested with an acid-based method.

Chatterton added that this method likely wouldn't be used for analyzing grains, as they tend to have little to no fructans.

"The lack of technology is what's been holding us back," commented Watts. "Now we have the technology, we just need to raise the money to pay for this (in research)."

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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