Feeding Metabolic Horses: Risky Business or Simple Solutions

Care : Health Issues

Mary Beth Gordon, Ph.D.

Senior Director, Equine Technical Innovation

The diagnosis of equine metabolic syndrome (EMS) has come a long way.

But even with recent advances and increased scientific interest in EMS, the disease can still be difficult to pinpoint, leaving horse owners frustrated with how to manage a horse with this condition.

In many cases, horses suffer acute and recurrent laminitis as a result of EMS. Early diagnosis and treatment, as well as ongoing oversight are key to successfully managing the condition. However, nutritional therapies for EMS can also be a helpful management tool and should be started before further complications arise.

What is Equine Metabolic Syndrome?

Equine metabolic syndrome is associated with obesity, accumulations of fat in specific areas of the body, insulin resistance, inflammation and laminitis.

Many times it can be difficult to distinguish EMS from PPID/Cushing’s disease, as many of the symptoms are similar. But the two diseases do not necessarily go hand in hand. The relationship between obesity, insulin resistance and EMS can be tricky, as not all obese horses are insulin resistant and develop EMS. In addition, some horses with EMS are not visibly obese or insulin resistant. However, the condition may reveal itself when they are faced with a stressor such as a sudden change in feed, management or trailering. Fortunately, through ongoing research, the relationship between the genetics, environment and management of susceptible horses is revealing itself as the key to understanding this disease and putting preventive measures in place to address it.

The following steps are nutritional therapies and management tools to help you manage a horse with EMS.

Reduce weight

Whether your horse has been diagnosed with EMS or is simply obese to begin with, the first step is to reduce body weight. The hallmarks of an effective weight-loss program are calorie control and/or reduction, reducing glucose and insulin response to consuming a meal, and if possible, exercise. Work with your veterinarian or nutrition specialist to determine the weight-loss regimen appropriate for your horse. Generally, a bodyweight reduction of 1 to 1.5 lbs. per day, with a reduction in body condition score (BCS) of 1 to 2 units in 12 weeks, can be expected with a reasonable weight-loss plan.

It is important not to starve EMS horses and to provide complete nutrition with enough fiber to keep the digestive tract running smoothly.

Eliminate or greatly reduce pasture

One of the biggest offenders in an obese horse’s diet is pasture. Factors such as type of grass, weather conditions and stage of maturity can affect the carbohydrate content of pasture, and elevate glucose and insulin concentrations. The fructan sugar found in grasses has been suggested as a contributing cause of pasture-associated laminitis, and research has shown that horses can consume substantial amounts of fructan grass via daily grazing. However, it is important not to overlook the overall sugar (sucrose glucose) and starch content found in grasses and the resulting higher insulin levels found in grazing horses versus horses eating hay.

Turning at-risk horses out only during early-morning hours, on cloudy days and in well-managed, shady paddocks; or using a grazing muzzle, can help control carbohydrate intake, but putting metabolic horses out on unrestricted pasture is risky. Until they lose weight and have normal insulin levels, turnout on drylots is recommended.

Feed hay and incorporate appropriate feeds

Metabolic horses not on pasture need to meet their roughage requirement through hay. In general, the minimum amount of hay offered should be 1.2 percent of body weight, split into multiple meals. Usually moderate-quality grass hay is recommended as legume hays, like alfalfa, tend to have higher calorie contents and may be consumed more quickly, which can be a problem for hungry horses needing to lose weight. Also, research shows that alfalfa hay is associated with higher glucose levels after consumption versus grass hay. Hay can be offered through a mini-hole hay net, slow feeder or other feeding device designed to slow down consumption rate and extend eating time.

The maximum amount of soluble carbohydrates in hay that is suitable for a metabolic horse has been recommended to be less than 10 percent NSC (NSC = sugars starch fructan). However, due to variability in hay, digestibility, and individual animal response, it is less about an exact number and more about taking multiple steps to reduce NSC intake in susceptible horses. Soaking grass hays can reduce additional water soluble carbohydrate (WSC) levels (30 minutes in hot water, 60 minutes in cold water, completely submerged with water drained before feeding). But because soaking can also leach other nutrients from the hay, it is important to balance the total diet with a supplement or small amount of concentrate. 

Due to the restricted amount of forage in the diet, along with most forages’ inherent nutrient deficiencies, a mineral supplement, ration balancer or low sugar/starch feed should be incorporated to balance the total ration. Horses with active laminitis that are very sensitive to dietary change can start on a mineral supplement such as Free Balance Mineral, fed according to recommendations (2 oz. per day for 1000 lb. horse). This will provide much needed minerals to support the body and help repair tissue.  From there, easy keeper horses do well on a ration balancer such as Enrich Plus®. With a feeding rate of 1 lb. per 1000 lb. body weight, it can be split into two small meals of 1.5 cups each. The balancer has a very low sugar/starch content (approximately 15% NSC) and has been shown to have a low glucose and insulin response to feeding in healthy horses. 

For horses (and their owners) seemingly struggling with the small feeding rates of restricted hay and a ration balancer, a low-calorie, extruded feed such as WellSolve W/C® (Weight Control) can be helpful.  Reducing forage to 1% of his body weight, along with 0.35% of his body weight in W/C (3.5 lbs. for 1000 lb. horse) can provide larger concentrate meals to the horse, while also extending meal time. The glucose/insulin response to W/C is very low and overweight horses on a weight loss program lost an average of more than 50 lbs. in 90 days on W/C without exercise. These horses also had improvements in cortisol, leptin and insulin response to glucose infusion.  Further weight loss was seen (more than 90 lbs.) when horses were exercised. Another option is WellSolve L/S®, shown to have a very low glucose and insulin response to feeding in research trials.  Additional studies demonstrated the benefit of providing mini-meals (approximately 2 lbs. of L/S) to further lower insulin response to feeding.  This feed contains added benefits of a therapeutic level of biotin, along with higher levels of omega-3 fatty acids to support these horses in the recovery process. 

Incorporate supplements with care

The restricted amount of forage in the diet, along with the nutrient deficiencies of most forages, should prompt use of a mineral supplement, ration balancer or low sugar/starch feed. The essential nutrients from these supplements will provide much-needed support to the body and help repair tissue.

There are many additional supplements that can be fed to metabolic horses, from magnesium to chromium to psyllium and more. They may help, but good data showing their effectiveness is lacking. The takeaway is that supplements may have a place, but as a support, not a standalone solution. Pasture restriction, calorie control, lowering the glycemic index of the diet, and nutritional support throughout the process are all required. Consult your veterinarian about what supplements are best suited to your horse. 

Feeding metabolic horses at maintenance and above

Once weight loss has begun, it is important to monitor your horse closely via BCS and weight tape, and make adjustments as necessary to the program. Ideally, horses should stabilize at a BCS between 4 and 5, with more sensitive, chronically laminitic horses maintained toward a 4. Some ponies are practically impossible to get to a 5 or less, with a BCS of 6 acceptable, especially if they started at an 8.

Once horses reach a healthier BCS, the ration can be altered for weight maintenance. Usually, just increasing the forage portion of the ration to 1.5 to 2 percent of body weight daily will stop weight loss. Stabilized horses may be able to tolerate small amounts of pasture grass (with restricted time, restricted grazing via muzzle or both), but they must be monitored very closely through blood work, body condition, body weight and cresty neck score.

If metabolic horses need to gain weight, calories should come from fat and fiber in the diet, not from soluble carbohydrates. This can be done through increasing hay or a low sugar/starch concentrate feed. For exercising horses, additional fat from oil is helpful, as it provides significant calories without increasing meal size or glycemic response.

Work to prevent EMS

It is important that the EMS horse’s basic nutrient requirements are met, including protein, vitamins and minerals. However, the most important factor of a prevention plan is avoiding obesity. The insulin resistance and inflammation that stems from being grossly overweight can be difficult to overcome once the cascade has begun. Identifying at-risk horses early, implementing sound nutrition and management programs, and monitoring them closely can improve their health and quality of life.

Options for feeding horses that are overweight and/or have EMS:

Condition Goal Forage Feed Options Notes
BCS >/= 7
Insulin status = normal
Weight loss
BCS = 5-6
Restrict Pasture
1.0 to 1.2% BW grass hay, small hole hay net
WellSolve W/C® Monitor with weight tape and BCS, go slowly, exercise if possible
Enrich Plus®
BCS >/= 7
Insulin status =
Weight loss,
mitigate glucose/insulin response to meal
Eliminate Pasture
1.2% BW grass hay, small hole hay net, soak hay with NSC > 12%
Free Balance® 12:12 Vitamin and Mineral Supplement Feed as many small meals, slow rate of intake, make changes very slowly, monitor with weight tape and BCS, exercise if possible
Enrich Plus®
WellSolve L/S® or WellSolve W/C®
Weight Maintenance
BCS 4–6
No IR or laminitis
Weight Maintenance Monitor and restrict pasture access
1.5 to 2.0 % BW grass hay
Enrich Plus® Monitor horse closely for increases in BW, BCS, cresty neck, IR status, laminitis
WellSolve L/S®
Strategy® Healthy Edge® or Equine Senior® Active
Weight Gain
Goal BCS 5–6
Increase calories, gain weight Monitor Pasture Access
1.5 to 2.0 % BW grass and/or some legume hay
Add calories via fat: oil or Amplify® Monitor horse closely for excessive increases in BW, BCS, cresty neck, IR status
WellSolve L/S® plus fat
Strategy® Healthy Edge®, Equine Senior® Active, Ultium®

Every horse is unique and so is their nutrition. Finding the right horse feeding program is paramount to helping your horse perform and feel the best. Find the right feed for your horse with our Feed Finder Tool.