Endocrine Metabolic Disorder
Endocrine metabolic disorder, also known as EMS, can be defined as increased fat deposits, insulin resistance, and a predisposition to laminitis, but the disorder can manifest in several different ways and researchers are exploring the possibility of different subtypes of EMS.
Identifying EMS, and taking steps to manage the disorder can allow a horse/pony to live a healthy and productive life. Vets diagnose EMS on the basis of history, clinical examination and the results of blood tests and radiograph/x-ray evidence of subclinical laminitis. Excessive drinking and urination may be evident. Although insulin resistance, obesity and laminitis, especially in combination with each other, are strong indicators of EMS not all obese horses/ponies have EMS and not all that have EMS are obese. Because many conditions, including diet, pain, and stress can affect blood glucose and insulin levels, diagnostic testing should be performed in a controlled manner in a low-stress environment and perhaps delayed until the feet have stabilised and are relatively pain free.
A laminitis flare is often the first clue in identifying EMS and tends to be slow in onset and there can be a history of recurrent episodes. Regional fat deposits on the crest of the neck, behind the shoulder, on the tail head or on the prepuce and mammary glands can be indicators of EMS. Insulin regulates glucose concentration in the blood and stimulates glucose storage in tissues. EMS horse/ponies have decreased tissue response to insulin in addition to increased insulin secretion, resulting in higher insulin concentrations than normal in the blood. EMS may be a predisposing factor for pituitary pars intermedia dysfunction (PPID/ Cushing Disease). Both are EMS and PPID can occur concurrently in middle-aged and older animals.
A number of factors can contribute to the development of EMS. Equines in their natural environment have a seasonal cycle of weight gain over the summer grazing season followed by weight loss over the winter. Under modern management systems feed is more constantly available, and this combined with restricted exercise means some individuals are very prone to gaining weight and developing insulin resistance. Fat produces inflammatory mediators that decrease sensitivity to insulin and result in constant, low grade inflammation.
Early EMS diagnosis is important as the prognosis for those horses or ponies who have suffered multiple previous bouts of laminitis and major structural damage to hoof laminae is less favourable.
Managing the diet is most important in controlling EMS. Reducing body weight of obese animals is essential. With effective weight loss insulin resistance should also improve. Blood serum insulin concentration can be monitored. However, equines with EMS may not lose weight easily. Total feed and forage intake should initially be restricted to 1.5% of bodyweight on a dry matter basis, but dropped to 1.25% if resistant to weight loss. Avoid sudden feed restriction which may further exacerbate insulin resistance, make changes gradually. Obesity may be exacerbated by laminitis, which may limit exercise. These animals appear to have increased appetites and will often eat continuously as long as feed is available. Infertility and abnormal reproductive cycles can occur in mares affected with EMS.
Thin horses/ponies with EMS should receive increased calories in the form of roughage and fat. Molasses-free beet pulp, top dressing with vegetable oils, and feeding low-carbohydrate, high-fat supplements can be used until a desired body condition score is reached.
Many horses with severe EMS cannot graze without experiencing laminitis flare-ups. For this reason, pasture access should be eliminated or severely restricted until body weight is in the desired range. Providing a balanced diet with respect to vitamins and minerals is especially important, as EMS horses are in an inflammatory state and many vitamin and minerals are important antioxidants
Some EMS equines can have limited access to pasture after effective management of obesity and insulin resistance, providing no evidence of active laminitis, but grass intake must be controlled, perhaps using a grazing muzzle and being careful about choice of pasture. If animals are sound then exercise can help with weight management, building up gradually and slowly being mindful to work on good consistent surfaces.
These animals should be managed under the input of veterinary advice rather than choosing supplements off the shelf and medical therapy may be of benefit.