What is Equine Metabolic Syndrome (EMS)?

EMS is an endocrine (hormonal) disorder in horses, similar to metabolic syndrome in humans, that is characterized by obesity, insulin resistance, and regional adiposity (abnormal fat deposits), which can predispose affected horses to chronic  laminitis.

What types of horses are affected? 

First and foremost, most horses do not suffer from EMS.  Most horses tolerate dietary carbohydrates (e.g. NSC, starch, sugar, fructan) quite well, and thrive on this important and readily available source of energy.   Performance horses in particular need sufficient NSC in their diets for work and recovery after exercise.  Too little starch and sugar in the diet can actually diminish athletic performance over time in non-EMS horses.

Tess the pony indulges

That being said, EMS can occur in any breed, however ponies, Morgans, Paso Finos, and horses that tend to be “easy keepers” seem to be most vulnerable to developing EMS.  It should also be noted that not all obese (fat) horses are insulin resistant, and not all insulin resistant horses are fat.

How do I know if my horse is insulin resistant (IR)?

Veterinary diagnostic testing (blood work) is recommended to confirm IR, but here are some other classic signs of insulin resistance in horses and ponies:

  • A classic sign of IR is a “cresty neck”, of which a clear correlation between neck circumference and IR has been documented.
  • Horses with regional deposits of lumpy or dimpled fat pads (e.g. behind the shoulder, around tailhead, over the loin), are suspect of being IR.
  • Horses that seem to gain weight rapidly, or blow up easily, particularly in spring with new pasture growth, relative to other horses may indicate IR.
  • Horses that are tender footed, and/or that demonstrate rings on the hoof wall, expanded white line and blood spots on the soles of their feet,  suggests mild, chronic bouts of laminitis and IR.

EMS is easily confused with other clinical disease such as Cushing’s Disease (a.k.a. pituitary pars intermedia dysfunction) and hypothyroidism due to similar clinical signs, despite different underlying causes.  It is very important to work with a trusted vet to ensure an accurate diagnosis if any of these conditions are suspected.

A word of caution, single blood samples for the diagnosis of IR can be very unreliable and misleading as several factors unrelated to EMS influence glucose and insulin levels (time and content of horse’s last meal, type of feed horse is adapted to, time of day sample is collected, stress level of horse), leading to false conclusions.  Taking multiple blood samples over several days, or utilizing techniques such as the euglycemic insulin clamp or a combined glucose insulin tolerance test (CGIT) are more involved, but can lend more validity to the lab analysis.  In any case, early detection of EMS and other endocrine disorders is preferable.

7 thoughts on “What is Equine Metabolic Syndrome (EMS)?

  1. Pingback: Prevention and Management of EMS in Horses | The Feed Room

  2. my Morgan has been diagnosed with laminitis, he is off pasture andis fed 1 cup of grow n win twice a day along with some hay that has beenwatered down for 12 hrs. does Nutrena have a feed that is comparable or better?

    • Hello Annie, Thank you for your question. Assuming your horse is in good flesh and maintaining well on the current diet, we would recommend Empower Balance.

      As a side note, we would encourage you to read this article on hay soaking. The length of time you are soaking your hay is longer than recommended, which introduces risk of microbial growth. No need to soak more than 1 hr in cold water or 30 min warm. Just drain off the liquid well afterwards, or you could find a source of tested hay that has a low NSC value (under 15% NSC).

      Good luck, and let us know if you have further questions! Thanks ~ Gina T.

  3. Will Nutrena offer help choosing the right feed and quantity of feed for a horse if the owner has a current hay analysis to work off of? I have always fed Nutrena feeds and been very happy with them. However I have a 10 yo QH gelding who was recently diagnosed with EMS and I am looking to get him on a more balanced feed program that more adequately provides for his vitamin/mineral needs without the added calories.

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