What's 'Sweet' in Sweet Feed?

All the rage these days in human diets is to take the sugars out of food and keep the carbohydrates to a minimum. This same principle, that of feeding a diet low in nonstructural carbohydrates (NSC), is being applied to equine nutrition. [Many horses do not require a commercial concentrate feed at all, if they can maintain their weight on forage and a mineral supplement alone, equine nutritionists note. But some horses need more.] Considering that horses are herbivores designed to extract energy from a very different sort of diet than that consumed by humans or carnivorous small animals, let's look at what "the sweet in sweet feed" (and hay) is all about, and put how to feed sweets safely into a practical perspective.

Remember: the most important reason horses get fat is they get too many calories, not that they get too much sweet.

What's Sweet in the Feed?

Many knowledgeable equine nutrition experts work with feed companies to formulate the variety of products you find at the feed store and carry home in 50-pound sacks to your eager horse. Karen Davison, PhD, manages equine technical services for Purina Mills. She explains about sugars and starch: "NSC, or nonstructural carbohydrates, are sugars and starches present in plants. They aren't dangerous to the horse, in and of themselves; on the contrary, horses, as grazers, evolved eating plants, which are the source of sugars and starches. Not only are NSC vital to provide energy to the horse, but simple and complex sugars play other important roles in the body. For example, glucosamine (a constituent of joints) is made up of sugar components."

Mary Beth Gordon, PhD, collaborates with Davison as a nutritionist at Purina Mills. She describes common NSC: "Fructan is a sugar storage component of plants, composed of many fructose molecules chained together, and it is stored primarily in leaves and stalks. Starch is made from chains of glucose molecules, also stored in the plant, particularly in the seed heads, or grains."

Keeping dietary sugars to a minimum is not just about limiting the sweet in the grain, but also in the forage. Kathryn Watts of Rocky Mountain Research and Consulting examines forage and grain components as part of her focus on diets for carbohydrate-intolerant horses. She explains, "Rapid plant growth rates use up sugar as quickly as it is made—sugar and fructan concentrations are lowest in fast-growing grass, and highest in slow-growing grass.

"Grain seed is mostly starch, although it can also contain some fructan," Watts continues. "Grain hays may have a lot of sugar and fructan left in the stems if conditions are bad, as in drought, frost, insect infestation, stem breakage, or hail damage, all of which retard seed formation." Even with good growing conditions, she notes that if more sugar and fructan is available than needed to form seeds (grains), the leftover remains in the stem (hay or straw).

One significant note is commercially prepared sweet feeds aren't always the high-sugar culprits. There are some sweet feeds that are higher in fiber and lower in sugar and starch than pelleted feeds or plain grains. For example, some plain oats can contain 50% more starch than a higher-fat commercially prepared sweet feed.

Health Hazards Related to Grain

Although commercial concentrate feed has been widely accepted for decades as a part of a horse's daily diet, it is not without a peculiar set of problems, and not every horse needs it. Restriction of forage in the diet creates conditions for gastric and colonic ulcers; notably less forage is fed if a horse is supplemented with concentrates that are high in calories and sugars.

Frank Andrews, DVM, MS, Dipl. ACVIM, a professor and section chief in the Department of Large Animal Clinical Sciences at the University of Tennessee veterinary school, has researched the effects of grain feeding on gastric health and ulcers. He explains that volatile fatty acids (VFAs) and fermentation products of soluble carbohydrates in grain contribute to damage of the stomach mucosa (lining), with subsequent gastric ulcers.

Andrews notes that the extent of injury to the stomach lining depends on the amount (dose) of concentrate (fermentable carbohydrates) ingested. If grain is included as part of the diet, current protective strategies recommend feeding less than one pound of grain per 220 pounds body weight. If, for caloric reasons, more concentrate is fed than this recommendation, then the "dose" should be limited by offering small amounts at least five hours apart. This limits a horse's intestinal exposure beneath a "threshold level" of Volatile Fatty Acids (VFAs). Your horse's ration should be weighed, rather than fed by volume, so you know exactly how much your horse is receiving.

Other health hazards, besides gastric ulcers, that are directly related to grain include:

  • There is an increased risk of colic associated with feeding five to 10 pounds of concentrate per day.
  • It is recognized that the high starch (and fructan) content of concentrate feeds (or pasture) increases a horse's susceptibility to developing laminitis.
  • Horses afflicted with PSSM (polysaccharide storage myopathy) do not do well on grain-inclusive diets, as this adds to the problems of abnormal accumulation of glycogen and glycogen-related polysaccharide (sugar) in skeletal muscle. Low NSC and high-fat feedstuffs should be substituted for high-sugar concentrates.
  • Sweet feed contains molasses, which is 6% potassium, a dietary component that is dangerous to feed horses with hyperkalemic periodic paralysis (HYPP, a genetic disease of Quarter Horses and derived breeds characterized by sporadic episodes of muscle tremors and stiffness, along with elevated serum potassium levels).
  • Many concentrates are fortified with electrolytes (salts) and/or molasses that contain potassium, so read the labels to know what your horse is getting.
  • Grains grown in stress conditions are susceptible to development of mycotoxins (mold byproducts) or to endophytes (types of fungus), such as in fescue hay.

Is Sugar All Bad?

Davison and Gordon stress that it is an oversimplification to think that all horse diets should eliminate "high-sugar" feeds. "That is similar to saying all people should eat a diet suggested for diabetics," Davison says. "There is tremendous variation between individual horses as to blood sugar and insulin response to a meal. Normal horses tend to be borderline ‘diabetic' as compared to humans, dogs, and cats. This was Nature's way of helping them handle the feast or famine in the wild, with lots to eat in the spring and summer and not much to eat in the fall or winter. Their ability to extract everything available from accessible forage helps them pack on stored energy to carry through the lean times. The problem for our domesticated horses is that it is ‘feast' all the time, yet they aren't working off the calories. The body runs out of room to store sugar and can only store fat; glucose then isn't driven into muscle cells, where there is already an abundance of sugar stored as glycogen."

Not all horses have problems with high-sugar concentrates, and some need relatively high NSC levels to fuel their type and level of performance—sprint racehorses, for example. Davison stresses that problems develop when a horse that is genetically efficient or is not engaged in regular exercise is fed more calories, regardless of the source, than are needed.

"These horses may have difficulty managing blood sugar levels, similar to a human Type II diabetic," Davison explains. "In humans, this is a heritable disease that is also affected by a sedentary lifestyle and obesity; some races of people have a much higher incidence of diabetes than other races, even when diet and exercise are similar.

"Certain breeds of horses tend to have more issues with higher sugar feeds," she continues. "Metabolically efficient breeds like Morgans, Quarter Horses, and drafts tend to have more metabolic issues from eating an overabundance of NSC than most Thoroughbreds. A metabolic problem, such as polysaccharide storage myopathy, is related to genetics and is best managed on a low-NSC, high-fat diet. Diet doesn't necessarily cause a horse to have the condition, but manipulation of the diet can help manage the condition." Regular exercise also is an important component for managing these horses.

Watts describes the carbohydrate-intolerant horse: "Hyperinsulinemia (or insulin resistance) is getting a lot of attention lately. The cells are starving for sugar, but the blood still has plenty of circulating glucose, which triggers fat formation and the release of even more insulin in an attempt to drive excess sugar into the cells. The more sugar thrown into the horse's system, the more insulin is produced, yet insulin resistance causes the horse to ‘starve' at the cellular level while laying down more fat. ‘Easy keeper' breeds tend to be more insulin resistant by design, like Native Americans or Eskimos, who cannot accommodate ‘fast food' loaded with sugar and starch. This is not necessarily a disease as much as it is an inappropriate diet. Certain breeds of horses are not genetically geared to eating grain, high-sugar grasses or hay, or molasses."

In many cases, "less is more," and concentrates should only be fed when free-choice hay or alternative fiber sources are not maintaining condition.

On the other hand, a horse that is working hard might need some NSC to maintain muscle glycogen stores to fuel exercise. Davison mentions a study (Topliff et al., at Texas A&M University) that revealed feeding a hard-working horse a very low-NSC diet resulted in muscle glycogen depletion within three days. Those horses lost performance, fatigued more quickly, and developed behavior problems.

Davison says, "The primary fuel source for brain and hoof tissue is glucose. For a hard-working horse, problems may develop from a diet that is extremely low in NSC components. But in general, the concerning issue for the general horse population is about feeding too much to horses doing too little exercise."

How Sweet It Is

Davison describes maintaining perspective on additional sweetening components in concentrate feeds and pellets: "Molasses, while high in sugar content, may contribute a lower amount than the sugar contribution from hay or pasture, and the digestion rate of the two is different. Potassium in molasses may be too high for HYPP horses, although most grains are lower in potassium than some pelleted feeds."

Gordon remarks, "Commercial feeds that advertise ‘low starch and low sugar' are available. However not all horses require such feeds. If a horse has a medical condition that specifically requires a low-NSC feed, choose one that is properly designed for the horse not only in NSC, but in calories and other nutrients as well. Feeding low NSC is not a ‘one-size-fits-all' situation. For example, a classic Cushing's horse may need more calorie and nutrient support than an overweight horse that needs fewer calories, yet both may benefit from a low NSC ration."

Davison urges, "It is important to look at the nutrient content of the total diet rather than just looking for a single ingredient and passing on that product due to its presence. The total nutritional picture should be considered to avoid future health issues created by an unbalanced or inadequate diet.

"Some horses are able to maintain their body condition on hay or pasture alone and don't need additional calories, yet may need protein, vitamin, and mineral supplementation," she adds. "There are products available that contain no grain, are low in calories and NSC, and can be used to provide balanced nutrition."

How Much Sweet is in the Bag?

To identify NSC content, a horse owner should directly contact the manufacturer. Unfortunately, there are no regulations that require information on the feedbag tag to accurately indicate NSC content. Watts says, "Owners of carbohydrate-intolerant horses can only review the ingredients and avoid grain products such as corn, oats, barley, or wheat, as well as wheat middlings (pollard, a byproduct of the wheat milling industry) and ‘grain products.' "

Davison points out, "Pelleting technology allows more diversity in ingredients, and many ingredients are lower in NSC. However, years ago, before the inclusion of higher fat levels, lowering the NSC also lowered the calorie content; then horses with high calorie requirements had to eat a much larger volume of feed. Modern fiber sources and the use of fat have enabled production of higher-calorie feeds that remain lower in NSC."

She stresses the importance of evaluating calorie content of a low-NSC diet. "A feed that is low in NSC and low in calories requires more quantity to maintain condition; then the horse ends up with a larger meal and, ultimately, at least as much NSC as he would if fed a product that is slightly higher in NSC, yet higher in calories so it could be fed in smaller amounts."

Davison is wary about lab testing: "Lab testing of any feed can be useful, but there are limitations to what a lab analysis can tell you."

The bottom line is to query the manufacturer about the "as-fed" calorie content, then compare it to other products on the same basis. "You may have to trial-feed a product to see how much it takes to keep your horse in good condition."

Alternatives to the Sweets

Many riders complain about dealing with "too much horse" when their mounts are on a concentrate diet, then the horses intimidate the rider and receive less exercise. This creates a vicious cycle where the horse receives excess energy and has little way to burn it off.

Watts remarks, "If this describes your horse, try eliminating all grain and switch to low-sugar hay and see if your horse is more relaxed, has a longer attention span, and remembers his manners better. Compare the situation to that of children hyped up on sugar trying to sit still in school and learn."

Davison comments about concentrate alternatives: "Beet pulp is a good energy substitute if it is used to replace part of the hay." Beet pulp, without added molasses, maintains a horse's glycemic response in a safe range. Up to a pound of beet pulp (dry weight) can be fed daily with no adjustments made to the amount of hay fed. For each additional pound of beet pulp fed, eliminate 1.5 pounds of hay from the diet.

In addition to feeding fat by using vegetable oil found on the supermarket shelf, commercial fat supplements include high-fat formulated feeds or rice bran. Davison explains, "Two cups of fat (oil) is equivalent in calories to 3.3 pounds of oats, 2.6 pounds of corn, or 2.5 pounds of sweet feed; fat is a concentrated energy source useful for putting weight on a horse. Care must be taken not to overfeed calories, as this puts a horse at risk of metabolic issues like insulin resistance. And, fat added to the diet may necessitate adjusting for other nutrients, like protein, vitamin, and mineral intake."

People-Created Problems

Davison says, "A big objective is for people to realize it is not necessary to ‘love' their horse with a feed scoop; instead, ‘love' them with a curry comb or a nice hack down a new trail. Overfeeding, regardless of what is overfed, is a huge part of the issue, as are frequency of meals and stabling. Confining a horse to a 12-by-12 stall most days of the week, and feeding large meals twice a day while only being ridden on the occasional weekend, is not an ideal existence for a horse. A horse needs more time moving around in turnout. Sedentary lifestyles are harder on horses than any individual dietary constituent. Horses evolved to graze and ‘forage' rather than to stand in front of a feed trough eating all day in one place. Their digestive system is much more motile and functional when they move around, bones and tendons stay stronger, and their attitude improves and stays better. A horse turned out on free-range pasture may travel as much as three miles a day while grazing."

Watts similarly notes, "The effects of obesity in horses are just starting to be researched. As in humans, fat is recognized as not just an inert tissue, but one that also actively releases inflammatory cytokines that affect many other body systems. Obesity creates insulin resistance even in individuals that are not genetically predisposed. Just as it is sound advice for people, keeping our horses in lean condition is imperative to long-term health. I fear too many owners feed horses for psychological reasons, or to alleviate the guilt of not making enough time for their needs. Food is not love. Of course a horse likes the sweet stuff, but do we feed our children hot fudge sundaes for breakfast because they like it?"

Take-Home Message: Everything in Moderation

Gordon stresses, "Grains, with associated sugars and starches, are not inherently evil for horses. The brain and hoof require huge amounts of glucose for proper function and health. Balance is key: do not overfeed, do not let your horse get overweight, and exercise him as much as possible, as nature intended."

Watts emphasizes: "We need to realize that a horse is not a cow, a pony is not a racehorse, an old horse is not a young horse. And that the way Grandpa fed horses is no longer applicable."

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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