The alphabet soup grouping of acronyms IR (insulin resistance), EMS (equine metabolic syndrome), and PPID (pituitary pars intermediare dysfunction also known as Cushing’s syndrome) represent an increasingly common and growing incidence of illnesses in horses between the ages of five and 15 years.
Despite their separate labels these illnesses share many similarities in metabolic hormone imbalances and organ distress. The individual labels themselves imply separate and specific illnesses of the horse. However, it may be more correct to recognize that each of these illnesses represent a phase on a sliding continuum of the same disease.
Upon closer examination into the lives and lifestyles of these horses, they collectively share common perils — inappropriate dietary intake, namely the overfeeding of sugars and starches, insufficient physical activity, and lifestyle distress.
These horses are initially referred to as ‘easy keepers’ and are considered to be the ‘air ferns’ of the horse world. Without proper management many ‘easy keepers’ will progress to manifest excessive weight and/or obesity, ‘hard cresty necks,’ peculiar fat deposits (i.e. lumpy, bumpy fat distribution over the body), and over time become increasingly prone to what appears to be ‘unexplained’ reoccurring episodes of laminitis or founder.
They are also at a greater risk to develop Cushing’s syndrome as they age. The metabolic dysfunctions of the body are shown in the hooves. The external clinical signs the affected horses display betray the severity and depth of their internal metabolic derangements.
These are very sick horses with broken metabolic pathways, hormonal imbalances, distressed digestive tracts and livers and unusually high levels of inflammation in their tissues. Aberrant glucose, insulin, leptin (this is the hormone that signals the horse to stop eating) and cortisol levels are commonly cited.
Yet our understanding of the abnormal metabolic values is far from complete. In fact, the number and degree of metabolic derangements discovered in the blood work and at the cellular level of the metabolic syndrome horse continues to grow exponentially. This is a complex disorder for which more questions than answers currently exist.
Proper and early recognition of a young horse that may be susceptible to metabolic syndromes is important because prudent horse-keeping management can stalemate the expression and progression of many metabolic troubles. Generally without mindful intervention, the health of susceptible horses declines gradually over many years. However, the ‘at-risk’ horses can be recognized by a trained eye long before an ‘official’ diagnosis is made.
The ‘at-risk easy-keeping’ horse commonly begins as the ‘easy-keeping’ foal, weanling, yearling and young horse. These young horses easily become overconditioned, even more so if their diets are overly rich. Originally Morgans, Fjords, Icelandics, pony breeds, miniatures and draft horses showed a familial predisposition to metabolic syndromes, however, breed exclusion is no longer the case with more breeds becoming represented.
Moderate body condition in a horse is always an important management goal regardless of the horse’s age. Weight in excess of the horse’s ideal demands that the horse step up its metabolic and hormonal resources to properly maintain the extra tissue. Unfortunately horses do a very poor job at metabolically upkeeping excessive weight. If the burdensome weight is carried forward over many years, rather than subjected to the natural seasonal cycle of weight gain and weight loss, the health of the horse gradually suffers.
The most effective strategies in dietary practices aim to minimize and stabilize blood sugar levels in response to feed and feeding activity. These practices in turn maintain the integrity and functionality of insulin and other hormones in the horse’s body. Therefore, it becomes imperative to venture a fishing expedition which minimizes the sugars in a horse’s diet even at a very young age.
Beneficial practices include supervised grazing, a steady supply of free-choice, low-sugar, high-fibre forage hays, elimination of all grains, sweet feeds, extruded feeds, and complete feeds or any other feeds with added sweeteners — especially including treats/crunchies/cookies.
When horses are able to access a slow, steady supply of forage throughout their day it alleviates digestive distress, blood sugar spikes, hormonal swings, boredom and stress. Adequate mineral supplementation is often necessary to offset dietary insufficiencies. For example, magnesium deficiencies, iron overload and copper and zinc levels are well known for their ability to impact glucose and energy homeostasis.
Diet is not the only source of glucose spikes and hormonal fluxes in horses. Any stressful event will release the hormone cortisol, which in turn increases the blood glucose in anticipation for a survival strategy. Chronic and prolonged stress or stressors as perceived by the horse’s physiology and biology hosts a cluster of negative metabolic consequences. Underestimated sources of stress in horses include but are not limited to infrequent or interrupted meal feedings, physical pain, demanding training schedules, confinement, social isolation, boredom, neglect, and emotional and mental distress.
Exercise and the freedom to move in the horse is critical to stimulate digestive flow, improve digestion, increase circulation, ensure optimum metabolism, regulate blood sugar levels and decrease stress. The activities of eating and foraging are perhaps the greatest forms of body movement for the horse. When not available, the horse suffers both mentally and biologically.
Maybe the best and the worst part about this collection of illnesses is their resistance to respond favourably or be cured or reversed by medical management, pharmacological intervention or supplements.
This grouping of horses may be the ‘canaries in the mine’ pointing to the weaknesses in modern-day horse husbandry which identify those practices that are not in alignment with the highest health of the horse.
The good news is that there is a growing awareness about horse-keeping practices that do benefit the ailing metabolic horse, and if initiated early on in the lives of many horses prevents the occurrence and expression of metabolic diseases.