Forage for the Sugar-Sensitive Horse

by Lynda M. Vanden Elzen

Salsa the mini mule devised her own grazing muzzle quite by accident. That’s one way to go on a diet!

Nearly every day, we receive a call from someone looking for low sugar hay for their sugar-sensitive horse.  Reasons for sugar-sensitivity in horses are varied, but the most common calls we receive are on behalf of horses who:

  • have Equine Metabolic Syndrome (EMS);
  • have Pituitary Pars Intermedia Dysfunction (PPID – commonly called “Equine Cushings”);
  • have foundered, currently or in the past; or
  • tend to be easy keepers / overweight.

Not every horse requires or will even benefit from eating a low sugar diet.  Growing horses, harder keepers, hardworking horses, and horses who are just generally not sugar-sensitive can benefit from a reasonable level of carbohydrates in their diets.  NSC values of up ot 18% on a dry matter basis can be acceptable, depending on the horse, according to Shelagh Niblock, BSc, PAS.  Shelagh is the Senior Livestock Nutritionist at Hi Pro Feeds and we consult with her regularly on behalf of a variety of clients.  As well, it has been shown that horses who are not sugar-sensitive may receive no benefit when being fed a low carb diet.  But for those who are sugar-sensitive, there is more to feeding them than just finding hay with an NSC below 10-12%.  What each horse needs depends on the reason for their sugar-sensitivity, and also on how they live, what they do, their age, etc.

Equine Metabolic Syndrome

Horses with EMS are insulin-resistant and tend to be generally overweight, and can develop abnormal fatty deposits on their necks, loins, and tailheads (though not necessarily in any or all of these places.)  They will tend to have high body condition scores and are prone to laminitis.  Stock horses, miniature horses, ponies, donkeys, paso finos, and morgans are at high risk for EMS, but any horse can develop EMS. For these horses, we find it tends to work best if they are free fed, usually in some type of slow feeding system, a higher fibre, lower sugar, moderate protein hay with a lower feed value.  If the horse is elderly and may have trouble chewing a high fibre hay, we can help the owner to find the highest fibre hay the horse can tolerate.  The goal for a horse with EMS is to reduce the amount of forage they consume by increasing the fibre in that forage so that the horse will eat it more slowly and feel more full.  Feeding set meals with time between when the horse has no forage available can cause spikes in insulin levels, and raised cortisol levels, which can be very problematic for horses who are already sensitive to the effects of high insulin and cortisol.   It is not just about the sugars in the hay, and feeding a low fibre, extremely high protein hay with a high feed value, or feeding in set meals,  may be detrimental.

PPID / Equine Cushings

Horses with PPID are a little bit different than EMS/IR horses, though horses can suffer from both at once.  PPID is caused by an enlargement or benign tumour on a portion of the pituitary called the pars intermedia.  This causes the release of higher than normal amounts of the hormone, ACTH, which causes the adrenal glands to produce too much of the hormone, cortisol.  High cortisol can cause insulin resistance in itself as well.  The disease presents with some or all of the following symptoms:

  • abnormal fat distribution primarily in the crest of the neck, tailhead, sheath, and above the eyes, sometimes simultaneously on a horse who is otherwise underweight (i.e. fat pads in some places even though the ribs are showing)
  • chronic laminitis
  • pot bellied appearance due to muscle loss along the abdomen
  • noticeable muscle loss, especially along the topline
  • excessive drinking and sweating
  • increased appetite
  • increased infections, sole abscesses, sinus infections
  • long and non or slow shedding haircoat (This symptom is not always present.)

For Cushings horses, we recommend a diet similar to what is recommended for EMS horses (low sugar, higher fibre, lower feed value).  The major difference for Cushings horses tends to be their loss of muscle mass, so we find many of these horses do better on a higher protein diet.  Feeding a low sugar forage (NSC of 10-12% or less) to Cushings horses is imperative, and the optimal amount of fibre depends on the horse’s overall body condition and dental health.  Because Cushings tends to be a disease afflicting older horses, their ability to chew coarser hay can be an issue.  It can also be quite confusing to look at some Cushings horses, as they will have sizeable fat pads in some places, and appear underweight in others.  Feeding extra protein will help the horse to gain back muscle while they lose the regional fat they have developed as a part of their disease.  As well, regular veterinary care is essential for these horses, as many of them require medication to control the symptoms of their disease.

Foundered Horses

The optimal diet for a horse who is foundered currently or was in the past depends upon the reason for the founder.  If the horse foundered as a result of EMS or PPID, then he must be evaluated as above in terms of his diagnosis in addition to his current health, body condition, and activity level, in order to determine his optimal diet.  Generally, a low sugar, higher fibre, lower feed value hay is ideal, and lower range protein levels tend to be ideal unless the horse has lost muscle as a result of PPID.

Easy Keepers / Overweight

In short, we find it tends to be ideal to feed easy keepers as if they have EMS, as outlined above.


There are many reasons why a horse may be sensitive to carbs in their diet, and it is not often as simple as finding a low sugar hay.  Fibre, protein, and feed value must be considered as well, and optimized depending on the horse’s individual situation.  If you take a look at our Testing & Nutrition page, you will find more detailed information on ideal fibre, protein, and sugar ranges on hay tests for various types of horses.  In addition, mineral balancing and anti-inflammatory supplements can be of help, but the focus of this article is forage.



“Equine Metabolic Syndrome: Causes, Signs, Treatment and Prevention” – My Horse University (““)

“Low Starch Diets: Manage Carbohydrates to Your Horse’s Best Advantage” – Shelagh Niblock BSc.Ag., PAS (

“Cushings Disease or Equine Metabolic Syndrome?” – Stacey Oke, DVM, MSc (

“Equine Cushings Disease: Equine Pituitary Pars Intermedia Dysfunction” – American Association of Equine Practitioners (

“Overview of Equine Metabolic Syndrome (Insulin dysregulation syndrome, Equine syndrome X, Peripheral Cushing disease)” – Merck Veterinary Manual (

Print Friendly