EDITOR’S NOTE: The entry below was edited to answer readers’ questions regarding the use of softening and penetrating agents.
Hoof Nutrition Intelligence is a twice-a-month web segment that is designed to add to the education of footcare professionals when it comes to effectively feeding the hoof. The goal of this web-exclusive feature is to zero in on specific areas of hoof nutrition and avoid broad-based articles that simply look at the overall equine feeding situation.
Below you will find the latest question and answer installment that you can share with your footcare clients.
Q: Can you explain the basics of equine Cushing’s disease and how it could affect my three horses?
By Kathleen Crandell, PhD.
A: Equine Cushing’s disease remains a diagnostic challenge for veterinarians and a management puzzle for many horse owners. Although commonly referred to as equine Cushing’s disease, the more correct term, pituitary pars intermedia dysfunction (PPID), better describes the condition.
The pituitary gland drives the production of hormones in the body to maintain homeostasis, or a state of balance in the body. PPID results from the abnormal (but benign) growth of a specific region of the pituitary gland called the pars intermedia. Growth of the pars intermedia occurs secondary to the degeneration of the hypothalamus, another region of the brain. The hypothalamus links the endocrine and nervous systems, playing key roles in controlling the horse’s thirst, hunger, sleep and mood.
As the pars intermedia grows, it produces excessive amounts of various hormones, most importantly adrenocorticotropin hormone (ACTH). While ACTH performs many important tasks, among the most renowned is its ability to affect cortisol levels. Frequently referred to as the stress hormone, cortisol controls several body functions, including maintenance of blood sugar levels when a horse is fasting, generation of energy during exercise and activation of the “fight or flight” response. It also plays important roles in detoxification, antioxidation and infection-fighting pathways.
However, excessive levels of cortisol wreak havoc on essentially every body system. Consistently elevated cortisol causes muscle-wasting, increases susceptibility to infection and contributes to insulin resistance and laminitis.
Current estimates suggest that 20%-33% of all horses develop PPID by the age of 20. This makes PPID the most common endocrine condition of horses.
In days gone by, veterinarians and owners relied heavily on the classic signs of PPID to make a diagnosis. Those included excessive hair growth or lack of seasonal shedding, recurrent laminitis, muscle-wasting and a pendulous abdomen, recurrent infections (such as sole abscess and skin infections), abnormal sweating patterns, excessive thirst, frequent urination and behavioral changes such as dullness or depression. Most of these clinical signs result from excess cortisol levels circulating in the body.
With an improved understanding of PPID, owners and veterinarians now recognize early signs of PPID:
1 Lethargy, decreased athleticism or poor performance.
2 Decreased muscling along the back.
3 Delayed shedding or excessive hair growth.
4 Regional deposition of abnormal fat pockets.
An earlier diagnosis allows horse owners to begin appropriate management strategies to control the progression of the disease.
In cases of suspected PPID, ask your veterinarian for a TRH test. This test involves obtaining a blood sample, administering thyrotropin-releasing hormone (TRH), and collecting a second blood sample exactly 10 minutes later.
If ACTH levels in the blood samples increase excessively in response to TRH, the test is considered positive for PPID. Advanced cases of PPID can still be diagnosed by identifying elevated ACTH levels in circulation.
A review of nutritional strategies for horses with PPID can be found in the Nutritional Management of Metabolic Diseases. In addition to diet changes, horses can be treated with pergolide, the only FDA-approved medication for PPID.
Together with medication, dietary changes, and exercise, horses respond well to nutritional supplements designed to support the coat and hoof.
Kathleen Crandell is an equine nutritionist with Kentucky Equine Research in Versailles, Ky.
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Like many significant achievements, Absorbine® grew out of humble beginnings—and through the tenacity of someone willing to question the status quo. In this case, it was a young woman in late 19th-century Massachusetts: Mary Ida Young. Her husband, Wilbur Fenelon Young, was an enterprising piano deliveryman who relied on the couple’s team of horses to make deliveries throughout the Northeast. Inspired by Mary Ida and Wilbur’s vision, Absorbine® has continued to add innovative products throughout the years — products used every day by horse owners around the world. Which is why, since 1892, we’ve been The Horse World’s Most Trusted Name®.