Equine Cushing’s Disease
Pituitary Pars Intermedia Dysfunction (PPID), also known as Equine Cushing’s Disease (ECD), is a progressive disease that mainly affects older horses and ponies. It occurs when the pituitary gland, which is located at the base of the brain, fail to communicate appropriately.
The pituitary gland normally communicates via nerves and blood flow to signal the production and release of many hormones into the horse’s bloodstream. When this normal communication fails, the pituitary gland becoming hyperactive and doesn’t recognise the hormonal signals that tell it to ‘switch off.’ As a result, too much Adrenocorticotropic hormone (ACTH) is produced. This in turn leads to increased production and release of cortisol from the adrenal glands, which are located near the kidneys. This overproduction of cortisol increases the levels of circulating blood glucose and therefore increases insulin production, which can lead to insulin resistance, a major risk factor for laminitis.
With careful veterinary and dietary management, many horses with PPID can remain happy and active well into their senior years.
The early signs are often very subtle, your horse may simply lose a little weight or they may take longer to shed their winter coat. However, as the disease progresses other clinical signs can include:
- Laminitis, this may be mild and chronic (long-term)
- A thick, long, curly coat even in the summer (hirsutism)
- Excessive drinking and urination (polydipsia/polyuria).
- Increased susceptibility to infections
- A “pot-belly” appearance
- Excessive sweating
- Muscle wastage
- Abnormal fatty pads in the hollow above the eyes
- Lethargy/ dull
- Blindness and seizures can occur in extreme cases, but this is very rare
Diagnosis & Treatment
In most cases, your vet will carry out a blood test to detect the levels of ACTH in your horse’s body. This is best done in autumn, as at this time of year it’s easier to distinguish between horses with and without PPID. Alternatively a Thyrotropin Releasing Hormone (TRH) stimulation test may be performed, which may work better in some horses. They may also test the levels of glucose and insulin in your horse’s blood. In horses with advanced PPID, clinical signs alone may be sufficient for a diagnosis, even so, your vet will probably need to take some blood samples so that they can monitor the hormone levels and the effectiveness of any treatment.
The drug most commonly used to treat horses with PPID is pergolide mesylate (brand name Prascend), a dopamine agonist, which helps to regulate the pituitary gland and reduce the clinical signs of PPID. In addition to drug treatment, simple adjustments to your management routine can help keep a PPID horse healthy and comfortable.
Turn Out & Forage: Grazing, particularly spring grass, can contain high levels of non-structural carbohydrates (NSC e.g. sugars, starch and fructans) and these will increase blood sugar and insulin. This will increase the risk of insulin resistance and laminitis in horse’s with PPID. Consider turning your horse out in the late evening, when the NSC levels are likely to be lower. In severe cases of PPID, you may need to remove grazing from your horse’s diet altogether and replace it with a low NSC hay. If you don’t know the NSC content of your hay, we recommend soaked for 6-12 hours prior to feeding. This will help to reduce the amount of sugar it contains. However, it will also lead to a loss of minerals, which must then be replaced in the form of a suitable hard feed.
Hard feed: Horses with PPID have difficulty maintaining normal glucose and insulin levels and this can increase the risk of laminitis. Feeding high levels of starch and sugar will exacerbate this and should be avoided. Thankfully, Connolly’s RED MILLS have a number of ultra-low starch feeds suitable for horses with PPID.
If your horse is maintaining weight well on forage only then Connolly’s RED MILLS Performa Care Balancer is ideal. However, if your horse struggles to hold weight, as can often be the case as they get older, we recommend Connolly’s RED MILLS Horse Care Ultra Cubes.
- A cereal-grain free, very low starch ration to help maintain normal glucose and insulin levels.
- High quality dietary protein, rich in essential amino acids, to help maintain muscle mass and avoid muscle wastage.
- A blend of antioxidants, including vitamin E, C and selenium, to help to support immune function, which is particularly important for horses with PPID as they are more susceptible to infections.
- Nutritionally significant levels of biotin and associated nutrients to help support hoof health.
- Two prebiotics, yeast and a natural, long-lasting gastric buffer to aid overall digestive health and efficiency, which is often compromised as a horse enters their ‘twilight’ years.
Regardless of which feed your horse receives it’s important to divide any hard feed into several small meals to help avoid peaks and troughs in levels of blood glucose and insulin.
Supplements: If needed, your nutritionist may also recommend specific supplements for horses with PPID and one of the best is Foran Equine Muscle Max. Muscle Max contains the essential amino acid L-Lysine to help support muscle maintenance. It also contains B-vitamins to support appetite and vitamin E to aid immune function, both of which are common concerns for horses with PPID.
Horses with PPID can have thick, curly coats, even in the summer, and as a result will probably sweat more. Horses with PPID also tend to drink and urinate more. Therefore, they will need higher levels electrolytes in their diet. In mild cases, simply adding some table salt to the ration may be sufficient. However, for more severely affected horses, particularly if they are still in some level of work, we recommend supplementing with Foran Equine Equi-Lyte G. As well as excellent levels of electrolytes, Equi-Lyte G also contains the powerful antioxidants vitamin E and C to support immune function.
In some situations, depending on the individual and what else is being fed, your nutritionist may also recommend a specific hoof supplement such as Foran Equine Hoof Aid. Similarly if weight loss is a concern adding some oil such as Foran Equine Kentucky Karron Oil to the feed can help supply additional calories, this emulsified flaxseed oil is also high in omega 3 fatty acids to support coat health and the immune system.
Other Management Tips
Weigh & condition score regularly: Some horses will maintain their weight well, whilst others lose weight easily. Regularly monitoring your horse’s weight and condition will allow you to detect changes early and if necessary adjust their diet accordingly. As horses with PPID can develop abnormal fatty deposits, for example fat around the eye sockets, it’s important that you make note of these too.
Dental Care & Worming: PPID increases a horse’s risk for periodontal disease and sinus infections, so frequent dental checkups are essential. Similarly, horses with PPID are extremely susceptible to internal parasites, as their immune systems are often compromised, so you should make sure you use an appropriate and effective worming program.
Farriery & Grooming: Hoof abscesses and laminitis occur more frequently in horses with PPID, so it’s vital that they receive regular visits from the farrier. During the warmer spring and summer months, it may also be necessary to clip your horse to keep them cool.
If your horse is diagnosed, or is suffering from PPID, don’t despair, with good nutritional support many horses with PPID continue to lead happy and active lives. The most appropriate feed and supplements will depend on your horse’s individual needs and so we recommend that you contact our expert nutrition team