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Veterinarian Technician April 2013 (Vol 34, No 4)

Equine Essentials: Feeding Equine Patients With Metabolic Syndrome

by Jennifer A. Wrigley, CVT

    Whether working in small animal medicine or large animal medicine, veterinary technicians can probably agree that many patients are overweight or obese. As in humans, obesity is associated with many medical complications in animals, including heart disease, type 2 diabetes, and orthopedic problems. In horses, a metabolic condition called equine metabolic syndrome (EMS) may also develop. This article discusses managing and feeding overweight EMS patients.

    Key Points

    • Appropriate exercise programs and dietary adjustments are vital to treating equine metabolic syndrome (EMS).
    • All feedstuffs, including forages and concentrates, should be evaluated for their nutritional contributions before they are fed to an EMS patient.
    • An EMS diagnosis is based on a general phenotype that includes a greater-than-ideal body condition score with regional adiposity (in areas such as the neck, the rump, the tailhead, and/or behind the shoulders); insulin resistance; and a predisposition to laminitis.


    Adiposity—the state of being fat/obese
    Digestible energy—the potential energy in a food that is digested and absorbed
    Insulin resistance—a physiologic dysfunction characterized by a reduction in the action of insulin on target tissuesa
    Nonstructural carbohydrates—simple sugars, starches, and fructans that are components of a normal plant cell
    Water-soluble carbohydrates—sugars and fructans that are soluble in water

    aFrank N. Equine metabolic syndrome. Equine Vet J 2009;29:259-267.


    The term equine metabolic syndrome was first introduced because EMS parallels the human condition known as metabolic syndrome. According to an ACVIM consensus statement developed by a panel of equine professionals, a general phenotype is associated with an EMS diagnosis.2 The patient typically has a greater-than-ideal body condition score (BCS) with regional adiposity; insulin resistance (IR); and a predisposition to laminitis.2 It is important to remember that not all EMS patients are obese or overweight; however, all EMS patients exhibit regional adiposity, whereas fat in generally obese equine patients is distributed more uniformly over the body. The key areas of subcutaneous fat deposits or regional adiposity are around the nuchal ligament (referred to as a cresty neck), at the tailhead, and behind the shoulders.2

    Evaluating the Patient and the Diet

    Diagnosis of EMS by a veterinarian should be quickly followed by a comprehensive evaluation of the patient and the patient’s current feeding regimen. Underlying medical issues or complications due to EMS require treatment by a licensed veterinarian to ensure good overall health of the patient. Nutritional adjustments and an approved exercise program are required to facilitate weight loss, which should minimize complications associated with EMS. The goal is to have the horse’s energy expenditure exceed its energy intake. After the initial evaluation, it is important to regularly monitor changes in BCS and the insulin blood level and to continue a regular exercise program. A BCS is an estimate of the fat stores in a horse’s body.1 This system is based on a scale of 1 to 9, with 1 representing an emaciated horse and 9, an obese horse.1 Typically, a BCS of 5 or 6 is considered ideal. Specific areas (e.g., neck, withers, shoulders, ribs, loin, tailhead) must be assessed to determine a BCS. If you would like to learn more about determining the BCS of horses, click here for a BCS chart.

    Diet Restriction


    Adequate forage intake is essential for maintaining normal gastrointestinal (GI) function and health in horses. However, most EMS patients require some degree of hay restriction to support weight loss. A general recommendation is to feed a daily amount of forage equal to 1.2% to 1.5% of the patient’s body weight.3 Because forage restriction can increase the risk of GI disturbance, possibly leading to complications such as colic, it is recommended to feed a daily amount of forage that weighs no less than 1.0% of the horse’s body weight.3 Forages include fresh pasture grass, preserved hay, packaged haylage products, hay stretchers, and alfalfa pellets.

    When restricting forage intake, owners should weigh hay on a scale to ensure that the correct amount is being fed; a portable hanging or fish scale works well. For example, to restrict the amount of hay to 1.2% to 1.5% of body weight per day, a 1000-lb horse would be fed 12 to 15 lb of hay per day. For horses that are accustomed to free-choice access to hay, it is appropriate to begin forage restriction at 1.5% of body weight per day. If the horse’s forage was already being restricted, it may be necessary to restrict forage to 1.2% of body weight to achieve weight loss.

    Ideally, the entire day’s ration should be weighed in the morning and fed throughout the day. It is important to prevent the horse from having long periods of time without access to forage. The daily ration of hay should be fed at designated times throughout the day to minimize forage-free intervals, thereby maintaining normal grazing-like behavior. Horses that consume hay quickly may require a hay net with small openings to encourage natural grazing behavior and help slow them down.

    Ideally, hay fed to EMS horses should be tested to ensure appropriate nonstructural carbohydrate (NSC) levels. NSCs are simple sugars, starches, and fructans found within plant cells.4 The goal is to reduce the glycemic and insulinemic response to feedings, so an alternative forage may be necessary if the current source is not suitable. A recommended NSC content of 10% to 12% (some suggest <10%) of dry matter is ideal for patients with IR.3 Unfortunately, it is not always cost-effective to test all hay because some barns may not have adequate storage for large loads or may have difficulty purchasing large quantities of the same cutting of hay. Some horses with IR are quite sensitive to the sugars and starches in certain hays; therefore, if testing is not feasible, the hay can be soaked in cold water for 60 minutes or hot water for 30 minutes.3 The rationale for soaking is to leach out some of the water-soluble carbohydrates (WSCs; sugars and fructans) to reduce the overall NSC level.4 It is important to remove the hay from the water before feeding so that the horse does not inadvertently consume the “sugar water.” This method has produced variable results in studies; therefore, it is not completely reliable.3 It is important to note that while soaking hay leaches out some WSCs, it also leaches out some essential soluble protein and minerals. Therefore, if this method is used to decrease the WSC level, the accompanying loss of protein and minerals needs to be considered when a complementary concentrate is selected. Commercial forages (i.e., cubed or bagged hay) with declared nutrient and NSC analyses are available. 


    Grass intake also requires adjustment to promote weight loss, but it is more difficult to control. While hay can be weighed and its calories estimated, the digestible energy intake of a horse at pasture can be difficult to estimate. Digestible energy is the potential energy (in a feed) that is actually digested and absorbed.4 In one study, it was estimated that ponies consumed 40% of their daily dry matter intake within only 3 hours of pasture turnout.5

    Another potential complication with pasture turnout and grazing is the increased consumption of NSCs, fructans in particular. Pasture forage studies have shown NSC content to be as high as 30% to 40% of dry matter.3 Fructans, which are carbohydrates found in cool season grasses, cannot be digested by mammalian enzymes.6 Fructans are fermented in the horse's hindgut, and the ingestion of large amounts of fructan have been associated with laminitis.6 Until a horse’s insulin sensitivity improves, which must be determined by a veterinarian, pasture turnout may need to be completely restricted by using a dry lot for turnout. Unfortunately, horses with IR may always require restriction of grass/pasture, especially when environmental factors favor NSC storage. These factors include spring growth, frost stress, periods of drought, times when grass grows rapidly, and sunny days. Studies that measured the NSC content of pasture at different times of day found that early-morning and/or late-night grazing is ideal for horses with IR.5

    If some grazing is permitted, use of a grazing muzzle may be indicated if it is tolerated by the horse. However, some problems may occur when using a grazing muzzle. Some muzzled horses may consume more grass than expected. In addition, wearing a muzzle may interfere with herd dynamics if the patient is turned out with other horses, and frequent muzzle use may cause sores.

    Other strategies for limiting grass consumption include short turnout periods, hand grazing (preferably during the ideal times of day [i.e., early morning and late night]), or use of a round pen or small turnout area. Some horses with IR may require restriction to a dry lot only.

    Grains and Concentrates

    Grains and concentrates in an EMS patient’s diet also require evaluation to determine their appropriateness. Concentrates such as sweet feeds containing oats, barley, and corn are high in sugars and starches and are therefore contraindicated. A diet of hay alone does not provide 100% of a horse’s protein, vitamin, and mineral requirements; therefore, some concentrate is needed as a supplement.5 To ensure that horses receive a balanced ration when fed concentrates with hay, it is important to adhere to the manufacturer’s feeding recommendations; however, many concentrates provide an overabundance of calories when the minimum recommended amount is fed. Balancer pellets (formulated to be fed at a rate of 1 to 2 lb/d depending on the patient’s weight) are an ideal supplemental feed for overweight EMS patients. These types of feeds are lower in calories and typically lower in NSC content than sweet feed–based concentrates and therefore reduce the glycemic response after meals (check with the manufacturer to confirm the NSC level). Balancer pellets contain a larger percentage of protein, vitamins, and minerals per pound, allowing a smaller volume to be fed. If a horse requires additional calories to maintain body condition because it is in work or is breeding, many suitable commercial concentrates with low NSC values are available.


    Dietary changes should be made gradually over 7 to 10 days. Once a patient has been transitioned to a new diet, 3 to 4 weeks should be allowed to pass before a reassessment is conducted and changes are made. It is important to allow a patient’s body time to adjust to a new diet. Earlier reassessment may be necessary if a patient seems to be having problems adjusting to a new diet and exercise regimen. Fresh water and a salt source (a salt block or loose salt) should be available at all times. Remember that patients on restrictive diets should not go for long periods (4 to 6 hours) without access to forage. Horses’ stomachs continually produce gastric secretions (i.e., hydrochloric acid and pepsin); therefore, when feed is not available to buffer the acidic environment of the stomach, horses are more prone to ulcer formation.


    Along with dietary changes, EMS patients should be put on an exercise program that promotes weight loss and insulin sensitivity. General recommendations for an exercise program include riding or lunging two or three times per week for 20 to 30 minutes per session.2 The goal is to gradually increase intensity and duration until the desired weight loss is achieved.2 Once the target weight or BCS is achieved, it is important to continue monitoring the diet and maintaining a regular exercise regimen. Horses with laminitis that cannot exercise as recommended may be confined to stall rest until their foot structures are more stable.


    Dietary management of an EMS patient may initially seem overwhelming to a horse owner, but it can become part of a daily routine without requiring much extra time. Veterinary technicians who are well educated on appropriate feeding and management of EMS patients can help support and assist owners as they transition their horses to a healthier lifestyle.

    Downloadable PDF

    1. Henneke D, Potter G, Kreider J, et al. Relationship between condition score, physical measurements and body fat percentage in mares. Equine Vet J 1983;15:371-372.

    2. Frank N, Geor RJ, Bailey AE, et al. Equine metabolic syndrome ACVIM consensus statement. J Vet Intern Med 2010:1-9.

    3. Geor RJ, Harris P. Dietary management of obesity and insulin resistance: countering risk for laminitis. Vet Clin North Am Equine Pract Clin Nutr 2009;25(1):51-65.

    4. Equi-Analytical Laboratories. Glossary of Nutrient Terms. www.equi-analytical.com/InterpretingResults/Glossary.htm. Accessed June 2012.

    5. Geor RJ. Pasture-associated laminitis. Vet Clin North Am Equine Pract Clin Nutr 2009;25(1):39-50.

    6. Longland A, Byrd B. Pasture nonstructural carbohydrates and equine laminitis. J Nutr 2006;136:2099S-2102S.

    References »

    NEXT: Management Matters: Management 101 for New Supervisors: Client Service


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