EMS - Equine Metabolic Syndrome

Horses showing signs of Equine Metabolic Syndrome (EMS) can be prone to laminitis at any time of the year, although the risk often increases during spring and autumn.

EMS is a metabolic disorder that can be significantly improved through appropriate dietary and lifestyle changes. Understanding the condition is the first step towards managing it.

Most people know that horses with EMS generally benefit from a diet low in sugars and starches (ideally less than 10%) together with increased exercise. However, EMS is not simply a matter of being overweight. 

Some horses with EMS are overweight, while others are not. Common physical signs include a distinctive ‘lumpy’ appearance, a cresty neck and areas of excess tissue around the tail-head, behind the shoulders and over the rump. Some horses may also develop general puffiness, a swollen sheath or swelling around the udder.

EMS is a metabolic disorder associated with the way the horse processes and utilises nutrients. It is not necessarily caused by eating too much food, but by an imbalance in the nutrients being consumed.

This is why simply starving an EMS horse by restricting access to forage is not necessarily the answer. Keeping a horse on a very short paddock, providing insufficient hay or using a grazing muzzle for long periods may reduce overall intake, but can also create physical and mental stress.

Managing EMS requires looking at the whole diet and lifestyle rather than focusing exclusively on sugar levels.

If sugar and carbohydrate content were the only factors involved in EMS and laminitis, it would be difficult to explain why some horses on carefully managed, low-carbohydrate diets can still develop problems.

Cresty Necks

While stallions and some breeds, such as Welsh and Spanish horses, naturally have more prominent neck crests, horses with EMS may develop a noticeably enlarged crest.

An additional ridge can develop above the horse's normal neck profile, giving the characteristic ‘cresty’ appearance.

Other areas of subcutaneous tissue may also become enlarged, particularly above the eyes, behind the shoulders, around the tail-head and over the sides of the rump. These areas are often described as ‘fat pads’ and contribute to the characteristic ‘lumpy’ appearance.

One interesting observation is how quickly a crest can change from relatively soft and wobbly to firm and prominent, sometimes seemingly overnight.

Dr Deb Bennett, PhD, has described the horse's crest as being made up of fibro-fatty subcutaneous (adipose) tissue, which has a texture similar to high-density foam.

Like a sponge, this tissue can hold fluid. Under certain metabolic conditions, fluid may accumulate within the tissue, causing the crest to become swollen and unusually firm.

This rapid change can sometimes occur following rainfall, particularly during spring and autumn when conditions encourage fresh grass growth.

For this reason, some horse owners monitor the feel of their horse's crest regularly. A sudden increase in firmness can be an important warning sign that dietary and management changes may be needed.

If the problem progresses, other signs may include stiffness, reluctance to move, a stronger digital pulse and sensitivity in the feet, particularly on hard ground.

As the horse's metabolic balance improves, the crest and other areas of puffiness may become softer. This is why managing EMS is not simply about reducing sugar and starch. The overall balance of nutrients in the diet also needs to be considered.

Rather than focusing on one individual mineral, such as magnesium, it is important to consider the balance of minerals, vitamins and amino acids and how they work together.

The Case of ‘Georgia’

Take the case of ‘Georgia’ as an example.

In her ‘Before’ photograph, Georgia had sore feet and was very reluctant to move, although she was not dramatically rocked back onto her heels. She showed some visible signs associated with metabolic imbalance, including puffiness around the eyes, but was clearly not obese.

Her owner believed she was already on a low-sugar diet. She was receiving hay every day and had access to a mineral bucket, yet she developed sore feet shortly after several days of rain.

Fresh green growth was clearly visible in parts of her enclosure. Even small amounts of new growth appearing after rain can be problematic for susceptible horses, and Georgia developed a bout of laminitis after nibbling on this fresh growth.

When a horse is experiencing sore feet associated with laminitis, removing fresh green growth from the diet is an important part of management.

Simply restricting access to grass, mowing the paddock or allowing other stock to graze it first may not be enough. Even small amounts of fresh green growth can be eaten surprisingly quickly.

Creating a Grass-Free Area

Horses with metabolic syndrome may benefit from spending time in a completely grass-free area, sometimes referred to as a ‘dry lot’. This could be a large yard, round pen, arena or track system.

Georgia was moved into a completely grass-free area. Her hay was soaked and her feed was reduced to suitable damp chaff with salt, Graze Ezy, SOS and Supreme MVA.

The ‘After’ photograph shows a remarkable improvement in her overall appearance and vitality after several weeks, and she was walking freely again.

When taking a horse off pasture, it is important that they continue to have access to suitable forage. Providing adequate hay helps maintain a constant supply of coarse, fibrous material through the digestive system.

Small-mesh hay nets can be useful because they slow the rate of eating and encourage horses to spend longer periods grazing on their hay.

Choosing Suitable Forage

Recovery time will vary between horses and depends greatly on how effectively their diet and environment can be managed.

Forage should be carefully selected. Avoid fresh, green hay and, for horses that are particularly sensitive, avoid feeds such as clover and lucerne.

Lucerne is often recommended for laminitic horses because its sugar content can be relatively low. However, it is also a high-potassium, low-sodium forage, and we have found it unsuitable for some horses with metabolic problems.

The overall mineral and nutritional balance of the diet needs to be considered rather than looking at sugar levels alone.

Reintroducing Grass

Once the horse has recovered and is stable, access to grass should be introduced very gradually and for carefully controlled periods.

Choose the most mature grass available and begin with extremely short grazing periods. Starting with as little as 10 minutes can be appropriate for a particularly sensitive horse.

It is easy to underestimate how much grass a horse can consume in a short period, let alone over three or four hours or an entire day.

Careful management is essential because horses that have experienced metabolic problems are often very susceptible to relapse. Avoid allowing them access to stressed, short, fresh green grass or rapidly growing pasture.

The goal is not simply to keep the horse hungry. It is to provide appropriate forage, balanced nutrition, exercise and careful pasture management while allowing the horse to maintain a healthy digestive system and lifestyle.