If your horse is obese, has fatty deposits along the neck or rump, or has experienced intermittent episodes of laminitis, he may very well be suffering from Equine Metabolic Syndrome (EMS), a condition which is unfortunately becoming increasingly common these days.
EMS horses are typically described as “easy keepers”, and the condition most commonly develops between the ages of 8 and 18. Interestingly enough, some horses have a genetic predisposition to developing EMS. This would include pony breeds, Morgans, Paso Finos, Arabians, Saddlebreds, Spanish Mustangs, Warmbloods, and donkeys. However, any horse can develop EMS, regardless of breed or sex.
Equine metabolic syndrome symptoms and diagnosis
When a horse has EMS, their body is unable to properly metabolize carbohydrates in the diet. EMS also affects their ability to release and utilize insulin, and therefore, these horses typically have higher than normal insulin levels circulating in the bloodstream.
Diagnosing this condition usually involves blood tests, as well as an evaluation of physical symptoms, and even if your horse has no history of laminitis, your veterinarian will likely want to get radiographs of the feet to check for evidence of P3 (coffin bone) rotation.
With blood tests, it’s important to note that diet, pain, and stress can all affect blood glucose and insulin levels, so testing may need to be performed at your barn or wherever the horse is stabled. If the horse is currently dealing with a laminitic episode, diagnostic tests should be delayed until the horse has recovered and is relatively pain free.
The most commonly used tests for EMS include the oral sugar test (OST), the oral glucose test (OGT), and insulin tolerance test. These tests can also be important for ruling out Pituitary Pars Intermedia Dysfunction (PPID), as that condition calls for a different type of treatment.
So once the diagnosis of EMS has been made, what’s a horse owner to do? Can Equine Metabolic Syndrome be reversed?
These two questions go hand in hand: if horses are managed properly, yes, they can and often do improve, but dietary and management changes will be a crucial part of this process. Here are some tips regarding dietary modifications and weight management for metabolic syndrome in horses:
- Cut out all grains and processed feeds, instead feeding a forage-based diet of late-maturity (low NSC) grass hay along with a comprehensive vitamin/mineral supplement or ration balancer.
- Use slow feed hay nets or feeders to ensure that your horse has hay on a near-continual basis, as this will help to regulate blood sugar.
- Eliminate or greatly reduce pasture grazing. If your horse can tolerate some grass, it’s best to allow grazing during the early morning hours as this is when sugars are lowest in grass.
- Another option for horses on pasture is the use of grazing muzzles. These can be a great tool for reducing grass intake. However, keep in mind that grazing muzzles should be used for no more than 12 hour per day.
- Increase your horse’s exercise by turning them out in a dry lot, creating a track system, and/or longeing or riding on a more frequent basis.
- Some horses may need medication to induce weight loss or help manage EMS. Your veterinarian can advise on this.
What does horse gut health have to do with it?
Another important factor appears to come into play with Equine Metabolic Syndrome, and that has to do with the gut microbiome. Researchers have learned that the types of microbes living within the GI system are strongly influenced by diet. In fact, the link between obesity, metabolic syndrome, and changes within the gut bacteria has been well documented in both humans and mice.
Once ignored by the medical and veterinary world, the equine gut microbiome has now become a focal point of research and scientists have learned that the trillions of microbes which colonize within the gut are actually a central metabolic hub of sorts, keeping many bodily systems (including the horse immune system) in balance (1).
Scientists have also learned that the types of microbes living within the gut can affect an animal’s energy absorption, gut motility, appetite, glucose, lipid metabolism, as well as fat storage within the liver. When the microbial population becomes imbalanced, a condition known as “metabolic endotoxemia” can occur, leading to systemic inflammation and insulin resistance in horses (3).
In fact, a hallmark in both obesity and metabolic syndrome in horses appears to be a systemic, low-grade inflammatory state (1).
More recently, related studies have been performed in horses, and one such study showed that the bacteria present in the large intestine of EMS horses are either overgrown or depleted when compared with the bacteria levels of healthy horses (2). Researchers from that study found that EMS horses had the following microbial disparities when compared with normal horses:
- An abundance of Verrucomicrobia bacteria, which other studies have shown to be a potential indicator of glucose intolerance;
- A lower number of Fibrobacter, a bacteria which contribute to the breakdown of fiber; and
- Lower numbers of Ruminococcaceae, which produce the volatile fatty acid known as butyrate which helps with nutrient absorption (2)
The good news is studies also show that both diet-induced weight loss, as well as the administration of probiotics (dietary supplements containing beneficial live microorganisms) and prebiotics (ingredients that feed the beneficial microorganisms) appear to reduce intestinal inflammation and help restore metabolic balance (3). Therefore, both prebiotics and probiotics supporting digestive health may be an instrumental part of managing or even reversing EMS.
Animal studies have also shown that probiotics can be a valuable tool in the prevention of obesity and metabolic disease (1).
It’s worth mentioning that healthy horses can experience disruptions in the gut microbiome on occasion due to stress from competition or travel or sudden changes in hay or feed; however, with these horses, digestive system balance is usually naturally restored in a short period of time. Animals undergoing chronic stress from illnesses such as EMS may not be able to naturally re-establish a normal balance within their gut microbiome without intervention though.
Therefore, when devising a treatment plan for your EMS horse, consider adding probiotics along with the recommended dietary and management changes, such as increased exercise, in order to get your horse on the road to recovery.
Green, M. et al. (2020). Microbial Medicine: Prebiotic and Probiotic Functional Foods to Target Obesity and Metabolic Syndrome. Internal Journal of Molecular Science, (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7215979/)
Elzinga, S. E., Weese, J. S., & Adams, A. A. (2016). Comparison of the Fecal Microbiota in Horses With Equine Metabolic Syndrome and Metabolically Normal Controls Fed a Similar All-Forage Diet. Journal of Equine Veterinary Science, 44, 9–16.doi:10.1016/j.jevs.2016.05.010
- Festi, D. et al. (2014). Gut microbiota and metabolic syndrome. World Journal of Gastroenterology. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4239493/)