FAQ's on Equine Metabolic Syndrome:

What is equine metabolic syndrome (EMS) ?

EMS is a recently recognized problem usually seen in very over-weight/obese horses.  Horses with EMS are "insulin resistant" and often "founder" (develop laminitis). The excess fat cells (adipocytes) in the abdominal cavity produce hormones that may contribute to insulin resistance, chronic, low-grade inflammation, & altered cortisol metabolism, although research is ongoing regarding the pathophysiology of EMS.

What is insulin resistance?

-a horse that has "insulin resistance" has very high blood levels of insulin;  a horse's insulin levels can easily be evaluated by your veterinarian- a blood sample is drawn and sent to an outside lab for testing; results are usually received within several days to a week; horses with EMS typically have normal blood sugar (glucose) levels

What are the side-effects/problems associated with high insulin levels/insulin resistance?

-high insulin levels alone can result in laminitis (founder); this is the big complication associated with EMS; horses with EMS often founder easily, especially with any exposure to sugars/carbohydrates in the diet

What is laminitis?

-laminitis is an inflammation of the lamina in the feet, which connect the coffin bone (P-3) within the hoof to the hoof wall; this inflammation results in swelling & heat and severe pain; a horse with laminitis is usually reluctant to walk, sore on both front feet (less often all 4 feet), stands with front feet camped out & weight shifted to the hindquarters, & walks as if "walking on egg shells". In addition to insulin-resistance, laminitis can also be caused by excess grain intake, excess lush grass pasture, excess cortisol levels caused by PPID (see below), excess cortisol-type drugs given as an injection, systemic illness (diarrhea- PHF, Salmonellosis, colitis; retained afterbirth/uterine infection), or excess weight-bearing by one leg (e.g. a horse with a fractured/injured leg may develop laminitis in the opposite "good" leg secondary to the extra-weight bearing required of that leg).

What does a horse with EMS look like?

-a horse with EMS is usually very over-weight with fat pads readily visible and a cresty neck; not all over-weight horses have insulin-resistance, but they are at higher risk of developing insulin resistance/EMS; there is some genetic predisposition to developing EMS

Are there other causes of insulin-resistance in horses?

-in horses, insulin resistance is usually associated with either EMS or Equine Cushing's Disease (= PPID).

What is Cushing's Disease or PPID (Pituitary Dysfunction) in Horses?

-Equine Cushing's disease, better described as Pituitary Pars Intermedia Dysfunction (PPID), is a disease in usually older horses where the pituitary gland produces excess ACTH, which stimulates the adrenal glands to produce excess cortisol levels. Horses with PPID are often also insulin-resistant, but can have normal insulin levels. Most (75%) horses with PPID have a long, curly haircoat that doesn't shed out in the spring. Some drink water in excess & thus urinate more, some have high blood sugar (glucose) levels, &/or some have secondary infections due to the high cortisol levels suppressing their immune systems.

How do I manage my horse with insulin-resistance?

-diet management is very important: limit the amount of sugars/fructans/starch/carbohydrates; these are measured as the % of non-structural carbohydrates (NSC) in the diet & should be <10 % in the diet (on a dry-matter basis); See the link below for more info on Sugar Content in Feeds

-the over-weight horse with EMS should also be on a restricted calorie diet to allow weight loss: provide hay + a "ration balancer"; feed no more than 1.5% of body weight/day in total feed (on a dry matter basis) or as recommended by your veterinarian; weighing hay can be helpful

-a horse with insulin-resistance secondary to PPID may be under-weight or a normal weight; sugars/NSC should still be low, but extra calories (in the form of fat supplements) may be needed to improve or maintain body condition

-consult with your veterinarian on the optimal feeding program for your individual horse's needs

-other medical treatment specifically for the primary problem may be recommended by your veterinarian: horses with EMS are often treated with thyroid supplements to increase their metabolic rate, help with weight reduction & address the insulin resistance; the primary treatment for PPID is an oral medication called pergolide; laminitis and any other medical problems needs to be specifically treated/managed as recommended by your veterinarian

What is a "ration balancer"?

-high protein supplement with vitamins and minerals: supplies minimum protein & amino acid requirements plus vitamins and minerals that won't be supplied by a hay only diet;

-usually have no additional carbohydrates/sugar that might be a problem for an "easy keeper" or a horse with equine metabolic syndrome/insulin-resistance or which are just not needed

-ensures the horse gets the minimum requirements of vitamins and minerals such as selenium

-usually are pelleted to ensure good mixing/distribution of ingredients- minerals can be sifted out to be left in the bottom of the feed tub by the horse

-there are several brands available: some have flax seed oil added, which adds omega fatty acids, or other oils

-only a small amount needs to be fed: usually about 1# per day per 1000# horse (0.5 #  2x a day)

-meant to be fed with a good quality hay; there are "grass-formula" ration balancers to be fed with grassy hay and "alfalfa-formula" ration balances, which are formulated to be fed with alfalfa hay

What about pasture for an insulin-resistant horse/pony?

-many over-weight insulin-resistant horses/ponies need to be taken off of pasture completely & kept on a dirt lot

-limited pasture is an option (< 1 hr/day); grazing in the early morning is best, when the sugar levels are lower in grass; sugar levels in grass are higher after a frost the night before;

-grazing muzzles are often very helpful- it allows the horse to be on pasture with his/her buddies and get some exercise, but still limits intake

What about exercise for insulin-resistance?

-exercise can be very helpful; however, if the horse has sore feet from laminitis or other lameness problems this may not be an option; in the horse/pony that's able to exercise, this can make a big difference to aid in weight loss & improve metabolism

Click on: Sugar Content in Feed and Forage from Colorado State University for more info on feeding a horse with insulin resistance.

Click on: Univ Minnesota Web Site on EMS  for more info on Equine Metabolic Syndrome & research on the topic.

For more info, also see our article on EMS from Fredonia Veterinary Clinic in Fredonia, WI- click on: More Equine Topics (EMS)