Hello, I have a cushing's mare who is really sweet, she isn't too bad yet but definitely has it. she isn't on pergolide yet, I will probably put her on it in a few years, depending on her condition. I don't know what to feed her, she is slightly overweight, but it's more of the muscle wasting so she looks like she is overweight. I don't know if I should feed her a high protein/low fat or a high fat/ low protein diet. Olivia
I'm going to take the liberty of providing medical advice as well as nutritional advice in your situation. My recommendation (with the support of your veterinarian) is to start your mare on pergolide now for her Cushing's Disease since she's already showing external signs of the condition, meaning it's progressed beyond the early stages. By the time you observe hirsutism (long, curly hair), the disease is in the later stages and treatment may not be as effective. Starting her on medication sooner rather than later may slow the progression of the disease and improve her quality of life so I encourage you to rethink your decision to wait.
Now for the nutrition aspect of Cushing's Disease. From your description, I'm guessing that your mare has developed a pot-bellied appearance that at first glance makes her look overweight but upon closer scrutiny is due to (as you suspect) muscle wasting. As horses lose muscle mass due to the constantly circulating levels of cortisol (stress hormone) that mark this disease, they appear to "sink" in their topline and in their abdomens. Therefore it is not uncommon for a Cushing's horse to appear be swaybacked and have a "hay-belly."
The next time your veterinarian pulls blood to recheck your mare's hormone levels associated with the Cushing's Disease, ask if a serum chemistry can be run at the same time to see how well her kidneys, liver and other systems are working. If everything seems to be in order, then I would not hesitate to put your mare on a high protein/high fat/high fiber diet. Notice that the only category that should NOT be high is sugars and starches, or simple carbohydrates. While horses with Cushing's Disease may have altered glucose (sugar) metabolism and even insulin resistance, they should have no difficulty digesting and absorbing protein, fat and fiber. Sources for these additional nutrients include alfalfa hay, soybeans or an amino acid supplement; powdered fats or oils with a healthy omega 3 to omega 6 ratio; and complex carbohydrates from high fiber feedstuffs like beet pulp.
I encourage you to body condition score (and weigh) your mare before gradually adding one of these products at a time to her current diet. Then every two to four weeks rescore and reweigh her to make sure you're on track.
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Dr. Lydia Gray is the Medical Director/Staff Veterinarian for SmartPak, where she guides research and new product development, answers questions on her Ask the Vet blog, and speaks around the country at various events such as Equine Affaire, Dressage at Devon, and the USHJA Trainers’ Symposiums.