Managing Cushing's Disease

Cushing’s Disease is the common term for Pituitary Pars Intermedia Dysfunction (PPID). Horses with PPID have an enlarged pituitary gland that doesn’t function properly and produces high levels of multiple pituitary hormones, including Adrenocorticotropic Hormone (ACTH).

Horses with advanced PPID may show the characteristic long hair coat that fails to shed properly, abnormal sweat patterns, excessive drinking and urination, as well as muscle wasting. Muscle wasting is particularly apparent in the topline and may or may not be accompanied by overall weight loss. Earlier stage clinical signs can include abnormal fat deposits, chronic infections, poor wound healing or a change in energy level or performance.

While often thought of as an “old horse” disease, PPID has been diagnosed in horses as young as 7 years old. Often, PPID can be well controlled with medication, particularly when diagnosed during the early stages of the disease. There are several diagnostic tests your veterinarian may choose from to help diagnose PPID.  

Several dietary considerations should be made for horses with PPID. Feeding high quality protein is key to support muscle maintenance and counteract muscle wasting to the extent that is possible. We need to be realistic that a horse who is far along in the disease process and has experienced significant muscle wasting, may not return to a pre-disease level of muscling.

When trying to build muscle, people often get caught up in the percent protein of a feed. In this case, changing from a 10 or 12 percent crude protein feed to a 14 percent crude protein feed often won’t make a noticeable difference. The reason for this is that the percent protein of the feed is not as important as looking at the fortification with lysine, methionine and threonine. These are the amino acids that are most commonly undersupplied by the forage portion of the diet.

In order to support PPID horses, we will often recommend adding an additional 1 to 2 pounds of Essential K® to the diet for a concentrated boost of topline-supporting amino acids.  

Some, but not all, horses with PPID also develop Equine Metabolic Syndrome. It is helpful to test PPID horses for Equine Metabolic Syndrome to fully understand their metabolic status and exact dietary needs. However, we generally recommend feeding any PPID horse a low NSC diet.

Easy-keeping PPID horses do well on a ration balancer, like Essential K®, which supplies very minimal NSC to the diet. Weight loss can be a symptom of PPID in some horses. These horses need additional calories beyond their forage. Adding a fat supplement, like K Finish®, to their ration balancer can be explored. Another option is to feed a full-intake feed that is also low NSC. Kalm ‘N EZ® and Senior Sport are both popular options to support the harder-keeping PPID horse. Essential K® can be added to either of these feeds to maintain topline muscling as discussed above.  

Keep in mind that while it is important to monitor the NSC intake through the grain portion of the diet, forage represents the majority of NSC intake for most horses and this should be monitored as well.    

Article By: Nicole Rambo, Ph.D.
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