Equine Metabolic Syndrome

Equine Metabolic Syndrome is an increasing concern in horses. The numbers of horses diagnosed with EMS is rising on a yearly basis.

What is Equine Metabolic Syndrome?

Equine Metabolic Syndrome (EMS) is a collection of symptoms that puts horses, ponies or donkeys at very high risk of laminitis because they cannot regulate their insulin levels. Equids with EMS typically show:

Insulin dysregulation
Obesity
Abnormal fat deposits (see below)
Frequent or recurring episodes of laminitis
Cycles of low-grade laminitis which may not be noticed
Poor hooves
Weight loss is very hard
Low energy/sluggishness
Very thirsty
Urinates a lot
Mares become infertile or have irregular cycles
Always hungry

Fat deposits in horses with EMS

It is important to understand the role of fatty deposits in EMS. Normally when horses put on weight

they will do so evenly across the ribcage, back, shoulders and rump. In horses with EMS they will show an uneven build up of adipose tissue (fat) along the Crest of the neck, Tailhead regions, shoulders, Sheath (for males), Mammary glands (mares) and in the hollows above the eyes.

Issues with Adipose Tissue

Insulin Resistance

Adipose tissue produces its own hormones which prevent insulin from working properly. Insulin is a

hormone released by the pancreas in response to high blood sugar. When food is digested it is broken down into sugars which are released into the blood stream. The rise in blood sugars cause insulin to be released, stimulating the body to utilise this blood sugar. Once used by the body e.g by muscles during exercise, blood sugars drop to normal levels again. If the horse doesn’t utilise all the sugar then the excess is stored as fat.

In obese horses, these excess fat cells (adipose tissue) cause a resistance to insulin. Insulin

resistance means cells do not respond to the release of insulin, so blood sugars remain high. The

lack of response to insulin means even more insulin is produced to try and reduce the blood sugar

levels. This is termed hyperglycemia. Continuously high levels of insulin in the blood directly leads to

laminitis.

Leptin Resistance

Excess adipose tissue also leads to leptin resistance. Leptin regulates appetite and signals to the

horse when it is full. Leptin resistance means that the horse has no mechanism to feel full and consequently feels the need to eat more. If food is readily available the horse will continually eat which can lead to more weight gain.