He’s an easy keeper. She didn’t shed her winter coat this year. He’s losing weight. She’s sore in the front.
If any of these statements sound familiar, you could be seeing the effects of one of these two common conditions.
Equine Metabolic Syndrome (EMS) is a collection of characteristic clinical signs which occur in horses, donkeys and mules. Individuals suffering from this condition are commonly overweight (BCS >6/9) with increased fat deposits over the crest of their neck and tail head (regional adiposity). EMS is thought to be the result of inability to properly metabolize carbohydrates in the diet due to insulin resistance (IR). IR commonly occurs in middle aged horses between 5-16 years old. Breeds predisposed to EMS include Saddlebreds, Tennessee Walkers, Paso Finos, Morgans, Arabians, Mustangs and Quarter Horses. There may be a genetic disposition, but the underlying reason for development is unknown at this time.
Diagnosis of EMS is achieved by identifying IR through elevated blood insulin and leptin levels on bloodwork. In addition to bloodwork, an initial physical exam and detailed dietary history are also important. A baseline body condition score (BCS) will aid future assessment of your horse’s condition. Response to treatment may be monitored at home using a weight tape and neck circumference measurements. Here’s a link to an article and how-to on body condition scoring.
Pituitary Pars Intermedia Dysfunction, or Cushing’s Disease as it is commonly referred to, is a collection of clinical signs which result from chronic high cortisol blood levels. In most cases, the pituitary gland which stimulates cortisol production via the hormone ACTH is enlarged and overactive. Horses with this disease commonly have a long, wavy hair coat which fails to shed in the spring (hirsutism), lethargy, weight loss and/or loss of top line. PPID typically occurs in older horses over 15 years of age.
Diagnosis of PPID is confirmed through bloodwork, which evaluates the plasma ACTH concentration. As many horses affected by PPID may have concurrent insulin resistance, your veterinarian may recommend checking their insulin and leptin levels in addition to ACTH.
A common complication of both these diseases is laminitis or “founder”, especially for horses with IR. Elevated insulin levels have been shown to promote decreased blood flow to the foot via vasoconstriction. This results in damage to the lamina, which forms the connection between the coffin bone (P3) and the inner hoof wall. Laminitis may result after consumption of high-carbohydrate feed (hay, pasture or supplements). Obese horses are also predisposed to laminitis because of the added weight which must be carried on their hooves. As a result, acute laminitis is a common presenting complaint for EMS horses without a history of grain overload or bacterial disease.
So your horse has these signs, what do you do now? In both cases, proper management of the syndrome is most important. Management of EMS is based on weight loss and proper exercise, with the goal of addressing your horse’s insulin resistance. Often we will recommend placing your horse on a medication called Thyroxin and/or the supplement Metaboral to increase their insulin sensitivity and therefore weight loss. We will work with you, to develop an individualized diet and exercise regimen for your horse.
While EMS is treated primarily by dietary changes, PPID is treated with the medication Prascend. Prascend contains pergolide mesylate, which works to inhibit the secretion of ACTH and therefore cortisol. The goal of this treatment is to improve your horse’s clinical signs and endocrine abnormalities.
| Cushings (PPID) | Equine Metabolic Syndrome (EMS) | |
| Clinical Signs | Older (> 15 yrs old.) Hirsutism or delayed shedding Weight loss or loss of condition Abnormal fat deposition Recurrent/chronic infections Chronic laminitis | Middle-age (ave. 5-15 yrs. old) Obesity/regional adiposity Chronic laminitis Insulin resistance |
| Therapy | Prascend (Pergolide) Body clipping Geriatric horse care (dentistry, nutrition, farrier) | Weight loss (Thyroxin) Metaboral Exercise Low-carbohydrate diet |
