It is not healthy for horses to be overweight. It may be one of the most serious health conditions a horse can have. Unfortunately many animal owners deem a degree of obesity as normal, acceptable and even desirable.
As a result, obesity is commonly disregarded. Nonetheless, as a horse moves from overweight to fat to obese the consequences to their health become dire. Most people readily recognize a thin horse and assume it is ill or has health risks, yet not so many owners are aware of the health risks and welfare issues associated with fat horses.
Some of the obvious consequences of obesity can be attributed to the simple accumulation of excessive adipose tissue. These adverse effects include ease of fatigue, heat intolerance, abnormal reproductive performance, fatty tumours, and accelerated osteoarthritic conditions.
That which is not so readily apparent about obesity is its devastating metabolic consequences. Adiposity alters insulin function in horses and it is through this pathophysiological pathway that many adverse medical consequences of obesity are being characterized.
Insulin is a hormone which effectively moves glucose from the circulating blood, across the cell membrane and into the cells where it can be used for cell metabolism. When horses become insulin resistant or insensitive to the effects of insulin they can no longer control their blood glucose levels and perhaps more importantly they can no longer nourish their cellular tissue.
- More from the Manitoba Co-operator: Probiotics, prebiotics and horses
Thus the consequences of insulin resistance for the entire body are profound. As insulin resistance progresses a number of health problems develop. Insulin resistance has been implicated in the pathogenesis of equine metabolic syndrome, pituitary pars intermedia dysfunction (also known as equine Cushing’s disease), developmental orthopedic diseases, systemic inflammation and laminitis/founder. Of these, laminitis is particularly concerning because of its painful and debilitating nature. Insulin resistance, obesity and laminitis are intricately intertwined.
There is good evidence that diets containing high-energy rations increase both blood glucose and insulin levels following consumption. Horses consuming these diets show exaggerated post-feeding insulin levels. Presently it is thought that the cell membranes become insensitive to insulin as a result of frequent peaks in blood glucose and therefore insulin concentrations.
The unnatural bombardment of cell membrane receptors with insulin appears to dull their sensitivity and interferes with the proper functioning. Over time insulin sensitivity within the body is significantly diminished. It is being proposed that such diets are responsible for altering insulin mechanisms in horses.
Diets that contain substantial “refined” and processed cereal grains and thus carbohydrates are at odds with the nature of the foods for which horses are adapted. Forage sources that are relatively high in non-structural carbohydrates further aggravate the insulin resistance in affected individuals.
In the healthy natural state, the acquisition of fat stores in preparation for winter is important for survival. When environmental conditions become harsh, fat stores are mobilized to sustain the horse. In nature, the period of environmental harshness is finite and the acquired fat stores are depleted prior to spring and the growth of new grass.
Today, most horses do not lose much weight in the winter and we have fat horses entering the winter whose bodies are preparing for a lean period that never arrives. Fat stores are not mobilized and become stagnant.
In many cases, horses continue putting on weight at a time when their bodies are designed to be losing it. Undoubtedly this confusion contributes to metabolic chaos, further disrupting the insulin messenger.
It is important to understand that obese horses are living with some degree of metabolic dysfunction. Each obese horse is uniquely sick and therefore utmost care and kindness must be undertaken with diet, movement and lifestyle programs to restore these horses to a place of wellness. Interestingly, the management tools undertaken to treat obesity will be similar to those management tools utilized to effectively prevent the occurrence of obesity which include calorie restriction, diet modification and movement.