Discussion on how and what to feed horses that are diagnosed with EMS, ID, PPID

EMS = Equine Metabolic syndrome

PPID = Pituitary Pars Intermedia dysfunction or Cushing’s

ID = Insulin Dysregulation

Description of each condition.  EMS – These are horses that have fat or adipose cells that produces a hormone that allows cortisol to increase in the body without much regulation.  This is a very similar scenario to horses with PPID or (old terminology) Cushing’s but the disease is created by different mechanisms and regulators. Insulin becomes disrupted thereby causing insulin dysregulation.  Horses diagnosed with ID have both high insulin AND high glucose concentrations circulating in the blood.  Obesity increases the risk for EMS.  Laminitis may be attributed to horses having EMS and/or PPID.  Minimizing available dietary carbohydrates, sugar, and starches is of paramount importance to managing these conditions.  Horses with a Body Condition Score of greater than 7 is a good clue that you need to adjust the horse’s available diet.

According to Amy Parker, PhD, metabolic horses need to consume diets low (less than 15% of the total diet) in sugars and starches. Avoid typical grains such as oats, corn, barley and added sugar such as molasses.  Aim for your diet choices to include concentrates that are below 10% in soluble sugars and his in digestible fibers such as beet pulp or soy bean hulls. You can increase calories through the addition of fat (vegetable or rice bran oils).  Be wary of very green and lush pastures.  These fields are high in soluble sugars.


Within 3-4 hours, the average horse can consume half of their daily caloric requirements.  It is imperative that grazing time is controlled in the metabolic horse. One trick to limiting sugar consumption from the pasture is to graze the horses when the sugar content is lower.  For instance – Several hours after sunset each day, the sugar content is lower in grass because the grass is utilizing the sugar storage to grow.  So turning out a horse at 4 am (lowest sugar content in grass) and bringing them in before the sugar content rises (10 am) is an effective method to limit sugar ingestion by your horse.  If the outside temperature is below 40 degrees F, then the growing period of the grass is muted therefore, the sugar content will be high in the morning. If warranted, a grazing muzzle (limits intake by 80%) might help eliminated over-grazing of your pastures especially when plant sugar content is elevated.


Hay should be your main calorie source for your horse.  Have your hay analyzed by a lab (try your state laboratory for assistance with this chore).  Metabolic horses should consume hay that is les that 12% NSC or Non-structural carbohydrate.  How do you apply this to your horse?

Example:  Your horse eats 22 lbs of hay that is 12% NSC, then he is eating 2.6 lbs. of NSC.  However, if he eats only 17.6 lbs of hay that is 15% NSC, then he is still consuming 2.6 lbs of sugar.


Cool Season Grass (Timothy, Orchard and Blue grass) = These grasses are high in sugar and can be higher in sugar based on when the grass was cut/harvested. Sugar will be lower first thing in the morning  (after growing) verses early evening when sugar is accumulating.

Legume Hay (alfalfa) = This hay is lower in NSC but high in calories (not necessarily from the sugar portion of the plant).

Warm-Season Grass Hay (Teff, some Bermuda grasses) = These hays are naturally low in NSC and are an ideal hay for metabolic horses.

Late Maturity Hays = lower in NSC.  As plants age, the sugar reduces but so do other nutrients expected in the hay.  Supplementation with minerals and vitamins may be necessary when Late maturity hays are fed.

Haylage = This forage has been found to generate higher a insulin response in metabolic horses so it is NOT recommended that you feed this forage.

The secret to managing a metabolic horse is to keep his/her weight managed and avoid obesity, select feeds based on your horse’s needs, and feed them properly.

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