Equine Metabolic Syndrome/Insulin Dysregulation: Don’t Forget About Protein

Research Update: high protein spikes insulin in horses with EMS/ID

When it comes to developing a diet for horses with equine metabolic syndrome/insulin dysregulation, recent findings show that a diet high in protein can play a role in increasing insulin levels.

Guest contributor Dr. Jane Manfredi joins us to explain.

Equine Metabolic Syndrome/Insulin Dysregulation: Don’t Forget About Protein

by Jane Manfredi, DVM, MS, PhD, DACVS-LA, DACVSMR (Equine)
Assistant Professor, Michigan State University College of Veterinary Medicine

When we think about ideal diets for horses with equine metabolic syndrome (EMS) and/or insulin dysregulation (ID), the first things that come to mind for many are to avoid grain and to minimize the nonstructural carbohydrate (NSC) content in the food.

Current recommendations suggest that NSC should be kept at <10-12% to avoid triggering an insulin spike that could lead to a bout of laminitis.1 To maintain a low NSC and yet allow the diet to have appropriate amounts of vitamins and minerals, owners often opt to feed a ration balancer vs. traditional grain.

This small volume of pellets can be fed at an NSC of less than 12% and is often recommended by veterinarians to supplement primarily hay diets.

Lowering insulin blood concentrations at rest and after meals is a goal to minimize laminitis risk, and owners are rightly frustrated when they don’t see improvements. “I’m soaking the hay, they aren’t on grain except for a ration balancer, they live on a dry lot, they are getting appropriate exercise, but I just can’t seem to budge the baseline or oral sugar test insulin concentrations” are common refrains in these instances.

While this issue could be related to the horse’s pituitary pars intermedia (PPID) status, the amount and type of exercise they are getting, the actual tested NSC content of the hay, and the presence of other chronic illnesses, another possible cause of the persistently high insulin levels that has been overlooked until as of late is the ration balancer’s protein content.

While not as important as overall NSC content in triggering insulin responses (Macon et al., 20222), recent work has shown that ration balancers with protein concentrations of above 30% can themselves cause insulin spikes (Loos et al., 20193).

In fact, EMS horses fed a ration balancer with 31% protein had a “9-fold greater insulinemic response” as compared to healthy control horses.

As some ration balancers are produced with protein in the 15% range, for EMS/ID horses that are having issues improving insulin regulation, a change to the lower protein ration balancer may be part of the solution to improving metabolic health.

This special report is sponsored by Micro-Phase™ vitamin and mineral supplement, the product of choice for horses with EMS/ID.


1. https://sites.tufts.edu/equineendogroup/files/2020/09/200592_EMS_Recommendations_Bro-FINAL.pdf, accessed 8/15/22

2. Macon, E. L., Harris, P., Bailey, S., Barker, V. D., & Adams, A. (2022). Postprandial insulin responses to various feedstuffs differ in insulin dysregulated horses compared with non-insulin dysregulated controls. Equine Veterinary Journal, 54(3), 574–583. https://doi.org/10.1111/EVJ.13474

3. Loos, C. M. M., Dorsch, S. C., Elzinga, S. E., Brewster-Barnes, T., Vanzant, E. S., Adams, A. A., & Urschel, K. L. (2019). A high protein meal affects plasma insulin concentrations and amino acid metabolism in horses with equine metabolic syndrome. The Veterinary Journal, 251, 105341. https://doi.org/10.1016/J.TVJL.2019.105341

Sponsored by Micro-Phase™


 Micro-Phase™ is:

  • Formulated to supply the nutrients missing from an all-hay diet.
  • Designed to fill in the nutritional gaps when hay and less than the recommended amount of fortified concentrate is fed.
  • Low in calories.
  • A palatable alfalfa-based pellet that can be fed alone or mixed with other feedstuffs.
  • Supplemented at a rate of 2 to 4 ounces per day.
  • NSC: 11%, ESC 2.9%.
  • Protein: 13%


  • Paige D.

    I have a gelding with EMS/ID issues. I once tried him on a ration balancer (TC 30%), and the protein level turned him into a monster. Very aggressive to the other horses, very pushy and confrontational with me, just overall practically a nightmare to deal with. I took him off it and switched to a different brand of vitamin/mineral supplement, and his normal temperament returned. I eventually found out about KPP’s Micro-Phase and now he’s been on it for a couple years. He gets a good helping of low NSC chopped hay and just 1 measuring cup of Cavalor Silhouette Feed to make him think he’s getting a good meal along with the other horses.
    However, I’m often worried over whether he has been getting enough protein to support normal muscle function. After reading this article, it puts my mind to rest for good, knowing that it is actually a good thing for him to get less protein. (not to mention keeping him from turning back into a fire breathing dragon!)

  • Susan L Hoffman

    This article was very informative. I was top-dressing my EMS horse’s feed with TC Balancer because I feed less than the recommended amoun of his feed (TC Senior Gold), but the Balancer is 30% protein, so I think I’ll skip the Balancer altogether. I might just increase his regular feed amount to make sure he’s getting enough vitamins/minerals, and because he actually could use to gain a few more pounds.

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