Equine Metabolic Syndrome and Cushing’s disease is on the rise.
These complicated diseases affect all classes and breeds of horses, with the incidence increasing in the older population of horses.
I recently made the decision to euthanize a mare with Cushing’s disease that I had bought as a breeding mare. Despite a pre-purchase exam, the mare, royally bred with a show record to match, was delivered to me with multiple signs of a metabolic problem. I remember the feeling I had as she walked off the trailer. My dreams shattered and any hope of raising a healthy foal quickly diminished. My focus shifted to helping her achieve a comfortable life. She was noticeably foundered, she had peri-orbital fat above her eyes, a potbelly, lethargy, muscle atrophy, a hard cresty neck, an abscessed tooth, and she drank and urinated excessively. My hope was that she was just insulin resistant and a diet modification would fix her. Deep down I knew she had Cushing’s and was advanced in the disease. How did this happen?
I had a vet exam done; she supposedly “passed with flying colors.” The research and work I had been involved with for ten years on founder and laminitis had groomed me well on recognizing even the slightest sign of a metabolic problem. My poor mare had every single one of them. I worked to help her throughout the year by modifying her diet, restricting grazing, rebalancing her minerals, etc. The mare responded well by growing out her foundered feet, gaining healthy weight and healing her multiple wounds. However, her top line remained atrophied, her neck remained firm and her excessive drinking and urination continued. I had to body clip her in May because she had not shed out. Her energy level was always low, and she didn’t run with the herd. In fact I only saw her lope three times. Unfortunately, she developed sub solar abscesses in both front feet in the beginning of August correlating with the seasonal spike of ACTH (AdrenoCorticoTropic Hormone). Her endogenous ACTH came back extremely high and I put her on Prescend (Pergolide).
I also have a now 18 year old mare (diagnosed with EMS at age nine with an elevated ACTH) that has done fabulous on Pergolide. I was hopeful that medicating this advanced mare would turn her around. It didn’t. In fact, she developed severe neurological symptoms, falling without warning on several occasions. The time had come.
I am one of thousands of horse owners who have dealt or are dealing with a metabolic disorder in their horse. The question is…… Why is the incidence of these disorders skyrocketing?
I had always been told that Cushing’s disease is due to an enlargement of the pituitary gland, which then produces excess ACTH, which causes the adrenal glands to produce cortisol (the stress hormone). Chronically elevated Cortisol drives up blood sugar, which leads to insulin resistance. There is another culprit called Equine Metabolic Syndrome. EMS is used to describe symptoms that mimic Cushing’s disease but there is no tumor. Recent evidence suggests the amount of stress a horses experiences may play a role in the development of the disease. When the horse becomes stressed, it produces ACTH, which stimulates the adrenal glands on the kidneys to produce cortisol. If the animal is chronically stressed, the ACTH, cortisol, and blood sugar levels stay high. This, over time, leads to insulin resistance along with founder, polydypsia, polyuria, and all the other symptoms that go along with this disease.
Proper diet and exercise will go a long way in preventing and reversing some of these metabolic disorders. Exercise is a key factor as it allows the horse to use up the extra blood sugar, thus decreasing the actual level of circulating glucose. If a horse does not get sufficient exercise, it is a good idea to use a lower starch feed. This will prevent spikes in blood sugar from high starch sources like molasses, corn, and oats. Talk to your feed dealer and look for a feed that has lower levels of starch and non-structural carbohydrates (NSC’s). A supplement like ExcelEQ which is high in Omega 3 fatty acids serve as an alternative energy source which provides calories while also suppressing inflammation.
In future postings, I would like to discuss how certain horses are more prone to developing some of these disorders based on their innate personalities as well as analyzing natural sources of Omega 3 fatty acids.