EQUINE METABOLIC SYNDROME

From: Diagnosis and Management of Insulin Resistance and Equine Metabolic Syndrome (EMS) in Horses by Nicholas Frank, DVM, PhD, DACVIM University of Tennessee

DEFINITION - ‘Equine metabolic syndrome (EMS)’ is a term that describes a series of clinical signs that contribute to the development of laminitis (founder) in horses.  EMS is most commonly seen in pony breeds, Morgans, Paso Finos, and Norwegian Fjords, although Arabians, Quarter Horses, Tennessee Walking Horses, Saddlebreds, Thoroughbreds, and Warmbloods have all been diagnosed with the syndrome.  In general, “easy keeper” breeds are at higher risk than “hard keeper” breeds such as Thoroughbreds and Standardbreds.  Identifying EMS in affected horses/ponies is important because proper management will aid in the prevention of laminitis. 

CLINICAL SIGNS  

·         Obesity and/or Regional fat deposits – These horses are often described as “Easy Keepers” because they require fewer calories to maintain body weight.  You may notice fat deposits in the form of a cresty neck, fat deposits close to the tail head, sheath, around the eyes, or as lumps on the body. 

·         Prior or current laminitis – Episodes may be triggered by grazing lush grass, or may have no identifiable cause.  Mild bouts of laminitis may go unnoticed by caretakers.

 

DIAGNOSIS – In the past, obesity and laminitis were associated with hypothyroidism but we now recognize that low thyroid concentrations can occur in horses with a variety of medical conditions.  Hypothyroidism is very rare in adult horses and can only be diagnosed by performing a hormone challenge.  The low thyroid hormones we find in obese, insulin resistant horses are a consequence rather than the cause of the problems seen.  Horses may develop obesity as young as 3 to 4 years of age, although most horses/ponies are between 5 and 15 years of age when veterinary or farrier services are first needed for a laminitic event.  As your veterinarian, we may suspect EMS based on clinical signs and perform one or both of the following tests:

·    Resting Serum Insulin Concentrations – This is a simple blood test that is often used as a screening test to detect moderate to severe insulin resistance.  You must keep your horse off of pasture for 12 hours and feed only hay overnight prior to having your veterinarian draw blood (eating either grass or grain will cause insulin levels to increase).  The pain and stress from an acute episode of laminitis will also cause insulin levels to be high, so these horses should not be tested until several weeks after the pain has subsided.

·    Combined Glucose/Insulin Test – This dynamic test is more sensitive and will detect mild insulin resistance.  As with the screening test above, horses must be held off pasture and fed only hay the night before the test.  A catheter may be placed the day before testing to make collection of blood samples during the test as stress free as possible for your horse. 

 

The day of the test your horse will be given a sugar solution intravenously, followed by insulin, blood is then drawn in 15 minute increments over the next hour.  How your horse’s system utilizes the sugar will tell us if he is insulin resistant or not.

TREATMENT

Goals: To improve insulin sensitivity and decrease the threshold for laminitis.  How?

·         Reduce body fat mass in obese horses

·         Avoid feeds that exacerbate IR

Weight loss in obese horses - Obese horses that are easy keepers should be placed on a simple diet of hay and a vitamin/mineral supplement.  Concentrates are not necessary for these horses.

Hay should initially be fed at 1.5%  body weight (15 pounds of hay for the average 1000 pound horse), then reducing this amount to 1.5% of ideal body weight until weight loss is achieved.  We carry a scale on the truck and would be happy to help with weighing your hay.

Just like you and me, DAILY exercise will help your horse/pony lose that extra weight; it will also increase insulin sensitivity, thus decreasing the risk of laminitis.  Horses and ponies with EMS should be walked on a lead rope, worked on a lunge line, or ridden daily.  If your horse is suffering from laminitis, wait to begin exercise until he is completely recovered.

Avoid feeds that will exacerbate IR - A horse with EMS is similar to a person with diabetes, excess sugar must be avoided.  Treats containing sugar and sweet feeds must be eliminated from the diet.  

Hay - It is also important to feed hay with low (<12%) non-structural carbohydrate (NSC) content.  NSC’s include simple sugars, starch, and fructans.  If the NSC of your hay exceeds 12%, soaking it in cold water for 30 minutes prior to feeding will lower the sugar content.  It does not matter if you feed grass or alfalfa hay as long as the NSC has been measured.  It has not been determined whether the protein, vitamin, and mineral content of mid-quality hay is adequate. In order to address these concerns, provide a balanced vitamin and mineral supplement, and sometimes a protein supplement may also be required. It may be particularly important to provide sufficient vitamin E, so we recommend that horses with EMS receive an additional 1,000 IU vitamin E daily.  Vitamin E can be purchased as a supplement for horses or in gel capsules sold at nay pharmacy or health food store.

Pasture - There is no way to control sugar intake if your horse grazes freely, and pasture grass is one of the largest sources of sugar in a horse’s diet.  Sugar levels of pasture grass fluctuate with season of the year and the time of day.  Access to pasture must therefore be restricted or eliminated when managing horses and ponies with EMS. Sometimes this is only necessary for weeks or months until the ideal body condition has been achieved, but other severely affected horses must be permanently housed in dirt paddocks because they are extremely sensitive to changes in pasture grass nutrient content. Most horses and ponies with EMS can be managed by limiting grazing time to 1 to 2 hours per day, housing in a grass paddock, strip grazing using an electric fence, or using a grazing muzzle.

Basic guidelines for lowering the risk of pasture-associated laminitis include avoiding times when the grass is 1) turning green and growing quickly (spring), 2) first drying out at the beginning of a summer drought, 3) rapidly growing after a heavy summer rain, and 4) entering winter dormancy (fall). In general, the horse or pony with EMS should be kept off pasture when the grass is in a dynamic phase. Pay attention to when your lawn needs to be mown more often because these are the times when your horse should be held off pasture.

Concentrates – Most IR horses will not need the extra calories provided by concentrates.  If you have a thin IR horse or an IR horse in heavy work, please see the section below “Management of Lean Horses with Regional Adiposity”.  Beet pulp may be used as a treat (0.5 cup after soaking) to aid in the delivery of supplements for obese horses. Remember to soak the beet pulp prior to feeding because this will lower the risk of esophageal obstruction (choke) and remove molasses if it has been added (use molasses free beet pulp).

DRUG THERAPY - Most horses or ponies with EMS can be effectively managed by controlling their diet, instituting an exercise program, and limiting or eliminating access to pasture. However, there are times when these strategies will not improve the situation fast enough to prevent additional episodes of laminitis. In these situations, drug therapy is warranted to lower the likelihood of subsequent laminitis episodes that could cause permanent damage to the feet. Weight loss can be accelerated and insulin sensitivity improved by administering levothyroxine sodium (Thyro L®, Lloyd, Inc., Shenandoah, Iowa) in the feed at a dosage of 48 mg /day for 3 to 6 months, which is equivalent to 4 teaspoons (tsp) per day.

When levothyroxine treatment is discontinued, do not stop abruptly. Horses should be weaned off the drug by lowering the dosage to 24 mg (2 tsp)/day for 2 weeks and then 1 tsp (12 mg)/day for 2 weeks.

 

  

Management of Lean Horses with Regional Adiposity

Some insulin resistant horses are leaner with respect to overall body condition, but have enlarged fat deposits (regional adiposity). Horses that are exercised regularly may have this appearance and these animals require calories for work. If hay is not sufficient to provide these calories, a concentrate must be selected.

Thinner insulin resistant horses can usually be safely fed concentrates, but care must be taken to provide calories without exacerbating IR. There are three considerations when evaluating feeds for insulin resistant patients: 1) the carbohydrate composition of the feed, 2) the glycemic response that will follow ingestion, and 3) the feeding practices of the facility. For instance, many sweet feeds have a high starch and sugar content, so the resulting glycemic response is likely to exacerbate IR when these feeds are provided as large meals. Feeds that contain less starch and sugar are more appropriate in these situations and it is advisable to feed smaller amounts more frequently and provide hay before concentrates. We use several strategies when managing leaner insulin resistant horses that require additional calories and the strategy used depends largely upon the appetite of the individual patient. These strategies include:

1.  Feeding a diet consisting of hay with a low (< 12%) NSC content, soaked molasses-free sugar beet pulp, balanced vitamin and mineral supplement, and 0.5 cup (equal to 125 mL; contains approximately 100g fat) rice bran oil or corn oil added to the feed twice daily.

2.  The same diet with a commercial low-starch specialty feed substituted for beet pulp.

3.  Feeding either of the two diets described above, with rice bran substituted for oil. Rice bran contains approximately 20% fat and we usually recommend that 1 lb (approximately 90 g fat) be fed twice daily.

4.  Feeding a pelleted feed designed for geriatric horses to older animals with pituitary pars intermedia dysfunction (PPID).

Horses with finicky appetites sometimes refuse to eat beet pulp or specialty pelleted feeds. If this is the case, clients may have to try several varieties of specialty feed until an acceptable one is found. These horses may also require a transition period as they adapt to the beet pulp or the specialty feed. During this period, we sometimes forced to feed oats with added rice bran or oil (in addition to hay) to horses that refuse lower NSC feeds. This is not an ideal diet for insulin resistant horses because oats contain more hydrolyzable NSC (e.g., starches) than most pelleted feeds, but we attempt to lower the glycemic response by feeding smaller meals more frequently (3 to 4 times daily) and asking clients to feed hay 15 to 30 minutes before concentrates.

Beet pulp is recommended for thinner IR horses because it provides calories, but it is not appropriate for obese horses, except as a treat (0.5 cup after soaking) to aid in the delivery of supplements. Sugar beet pulp is rich in rapidly fermentable carbohydrate, so addition of this ingredient to pelleted feeds lowers the hydrolyzable carbohydrate content. It also expands when soaked in water, so beet pulp provides bulk to satisfy the horse's appetite. Clients should soak the beet pulp prior to feeding because this will lower the risk of esophageal obstruction (choke) and remove molasses if it has been added.

Above is from: Diagnosis and Management of Insulin Resistance and Equine Metabolic Syndrome (EMS) in Horses by Nicholas Frank, DVM, PhD, DACVIM University of Tennessee

Examples of very low starch and sugar feeds:

·    Alfalfa pellets

·    Other hay pellets

·    Beet pulp, low molasses content - soak in water

·    Complete feeds - meant to replace hay if needed

·    Dengie or chaff products

·    Chopped hay products

Examples of low starch and sugar feeds*:

*In general, feeds higher in protein and fat will be lower in starch and sugar. Ingredients such as soy hulls, beet pulp, bran, wheat brans, and wheat middlings are relatively low in starch and sugar.

Below are examples of low starch and sugar feeds, there are many others. If in doubt, contact the company and ask about starch and sugar content. Look for feeds no more than 33% starch and sugar.

If you can see grains in the product it is likely too high in starch and sugar for an IR horse.

·    Nutrena Safe Choice

·    Senior feeds

·    LMF Stage 1

·    LMF Complete

·    Equi-Pro Carb-Safe

·    Platform horse feeds

·    Triple Crown Senior, Complete, Growth

·    Triple Crown Lite

·    Triple Crown Low Starch

·    Purina WellSolve L/S and W/C 

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