Metabolic Disease



Equine Metabolic Disease

Introduction

Equine metabolic diseases are among the most common—and most misunderstood—medical conditions affecting horses today. Disorders such as Equine Metabolic Syndrome (EMS) and Pituitary Pars Intermedia Dysfunction (PPID, commonly called Cushing’s disease) significantly increase a horse’s risk for laminitis, weight gain, and long-term health complications.

Unlike many illnesses, metabolic disease often develops slowly and quietly. By the time obvious problems appear, such as laminitis, the underlying condition may already be advanced. Early understanding and proactive management are key to protecting your horse.

What Does “Metabolic Disease” Mean?

Metabolic disease refers to conditions that disrupt how the horse’s body regulates hormones, insulin, and energy use. These disruptions affect how sugars are processed and stored, leading to abnormal fat deposition, inflammation, and hoof damage.

Two primary conditions fall under this category:

  • Equine Metabolic Syndrome (EMS)

  • Pituitary Pars Intermedia Dysfunction (PPID)

Although they share similarities, they are distinct diseases and require different management strategies.

Equine Metabolic Syndrome (EMS)

What Is EMS?

EMS is a disorder characterized by insulin dysregulation, meaning the horse’s body does not respond normally to insulin. This leads to elevated insulin levels, which directly damage the laminae in the hoof.

Common Risk Factors

  • Overweight or obese body condition

  • Regional fat deposits (cresty neck, tailhead, shoulders)

  • Easy keeper breeds (ponies, Morgans, Arabians, warmbloods)

  • Limited exercise

  • Diets high in sugar or starch

Clinical Signs Owners May Notice

  • Difficulty losing weight

  • Fat pads that persist despite calorie restriction

  • Recurrent or unexplained laminitis

  • Foot soreness without obvious cause

Why Laminitis Is Central to EMS

In EMS, laminitis is often triggered by high insulin levels rather than inflammation or mechanical stress. This is why EMS horses may develop laminitis even without grain exposure or lush pasture.

Pituitary Pars Intermedia Dysfunction (PPID)

What Is PPID?

PPID is a neurodegenerative disease of older horses that affects the pituitary gland. It results in abnormal hormone production, which can worsen insulin dysregulation and immune function.

Common Risk Factors

  • Increasing age (most commonly over 15 years)

  • Concurrent metabolic disease

  • Seasonal hormonal fluctuations

Clinical Signs Owners May Notice

  • Delayed or abnormal shedding

  • Long or curly hair coat

  • Muscle loss along the topline

  • Lethargy or decreased performance

  • Increased drinking and urination

  • Recurrent infections

Important Note

Not all PPID horses have classic hair coat changes early on. Subtle signs may appear years before diagnosis.

Diagnosis: Why Testing Matters

Because EMS and PPID can look similar, diagnostic testing is essential.

Veterinarians may recommend:

  • Resting insulin or dynamic insulin testing (EMS)

  • ACTH blood testing (PPID)

  • Seasonal interpretation of results

Accurate diagnosis allows for targeted treatment and avoids unnecessary or ineffective therapies.

Treatment and Daily Management

Dietary Management (The Foundation of Care)

  • Feed low non-structural carbohydrate (NSC) forage

  • Soak hay when recommended to reduce sugar content

  • Avoid grain and sweet feeds unless prescribed

  • Restrict or eliminate pasture access when necessary

Dietary control is the single most important factor in managing metabolic disease.

Weight Management and Exercise

  • Gradual, safe weight loss improves insulin sensitivity

  • Regular exercise (when sound) is highly beneficial

  • Exercise plans should be tailored to laminitis risk and hoof health

Medical Management

  • Pergolide is the standard treatment for PPID

  • Some EMS horses may require medication for insulin control

  • Hoof care is critical in laminitic horses

Medication works best when combined with proper diet and management—not as a substitute.

Long-Term Outlook and Prevention

Metabolic disease is manageable but not curable. With consistent care, many horses live long, comfortable, and productive lives.

Long-term success depends on:

  • Ongoing veterinary monitoring

  • Seasonal reassessment of diet and hormones

  • Owner vigilance for subtle changes

When to Call Your Veterinarian

  • Sudden or recurrent laminitis

  • Unexplained weight gain or fat deposits

  • Abnormal shedding patterns

  • Lack of response to diet changes

Early intervention can dramatically improve outcomes.