Pituitary pars intermedia dysfunction (PPID)
Did you know more than 20% of horses over the age of 15 and more than 25% of horses over the age of 20 may have PPID or ‘Cushing’s syndrome’? There’s no breed or sex bias and although the condition seems to be more common in ponies than horses, this may be just because ponies tend to live longer.
This guide is full of tips for managing horses and ponies with PPID but for specific advice, contact our team of friendly nutrition advisors, especially if your much-loved senior has a history of laminitis or is severely insulin dysregulated.
What is PPID?
PPID is a common endocrine or ‘hormone related’ condition involving the pituitary gland. The pituitary gland, which is located at the base of the brain, produces, stores, releases and regulates several different hormones. In healthy horses and ponies, the production of many hormones by the pituitary gland is controlled by dopamine – a hormone and chemical messenger that is also produced in the brain but by a different gland. In those with PPID, a reduction in dopamine results in the pars intermedia or ‘middle lobe’ of the pituitary gland becoming enlarged and over-producing several hormones including adrenocorticotropic hormone or ‘ACTH’ but exactly how this increase in hormones leads to the various clinical signs of PPID is still unclear.
Did you know? Together with our collaborators around the world, we are carrying out scientific research to help improve knowledge of how to diagnose, monitor, treat and manage horses and ponies with PPID.
Clinical signs
Clinical signs are varied and include:
- Excessive coat growth (hypertrichosis) that may become long, matted and curly, especially around the legs. That said, some horses and ponies may just have a few abnormal hairs!
- Failure or later shedding of the winter coat
- Muscle wastage
- Excessive sweating
- Increased drinking and urination
- Lethargy and poor performance
- Depression
- A pot-bellied appearance
- Weight loss
- Abnormal fat distribution including above the eyes, around the tail head and a cresty neck
- Delayed wound healing and an increase in infections of the skin
- Increased susceptibility to internal parasites and resistance to wormers
How is PPID diagnosed?
Diagnosis is often made based on clinical signs and a blood test to measure the concentration of ACTH in the blood, with results above a certain level being considered ‘positive’. If the result falls in the ‘grey area’ between the thresholds for a positive and negative test, your vet may recommend a modified blood test called a TRH stimulation test.
Every horse is an individual!
No two seniors are the same, including those with PPID. While some may be retired, underweight and showing multiple signs of ageing, others may be in good or overweight condition and/ or in active work, which means there’s no one size fits all approach to feeding or management. Ideally, ACTH and insulin status should be monitored regularly, so discuss this with your vet. In addition, look out for signs of dental issues as well as changes in behaviour, condition, muscle development and health, as feed and management requirements may change over time.
The laminitis link
Many but not all horses and ponies with PPID are also insulin dysregulated putting them at increased risk of laminitis (testing all horses and ponies with PPID for insulin dysregulation is recommended). However, we advise managing all horses and ponies with PPID as if they are prone to laminitis, which in general, means restricting starch and sugar intake and achieving/ maintaining a healthy body condition.
Monitoring weight & body condition
Monitoring weight and body condition in those with PPID can sometimes be a little more challenging – for one thing, a long thick coat can hide a multitude of sins!
Some horses and ponies may have large regional fat deposits such as a cresty neck or fat pads over the loins despite being thin over-all so in these situations, body condition scoring systems need to be used with care. On the other hand, muscle wastage can sometimes be mistaken for fat loss.
Forage
Ideally provide as much forage as your horse or pony will eat (while being mindful of excess waste) but remember:
Forage only diets are unlikely to provide a balanced diet and may be lacking in key nutrients including copper, zinc, selenium, vitamin E and lysine (quality protein).
Good doers may need some form of forage restriction, especially if they are already overweight – see our tips for senior slimming for more advice.
Those with dental issues may need a full or partial hay replacer.
To restrict or remove access to grazing, especially during high-risk periods such as on sunny frosty mornings and during spring and autumn grass flushes.
Soaking hay helps to reduce the water soluble carbohydrate (WSC) or ‘sugar’ content but results are highly variable. Ideally have your forage analysed (for WSC using the wet chemistry method) and feed soaked hay as a back-up. Soaking also results in a loss of some vitamins, minerals and soluble protein which means feeding a balancer (or suitable feed with added vitamins and minerals) is of increased importance for those fed soaked hay.
Bucket feed
Balancers are ideal for those able to maintain weight easily on forage alone.
If additional calories are needed, choose fibre-based feeds that are low in starch and sugar. Feeds high in oil (as opposed to cereal starch) are ideal for poor doers.
Contact a nutrition advisor before adding oil on top of your horse’s current feed to ensure the total diet provides enough vitamin E. Any oil fed should be fresh and introduced gradually.
As a guide, restricting starch and sugar intake to less than 0.5g per kilogram of bodyweight per meal (less than 250g per meal for a 500kg horse) should be suitable for most horses and ponies provided they are not severely insulin dysregulated.
Divide feeds into multiple small meals, this may be especially important for those who are insulin dysregulated.
As horses and ponies with PPID may be at increased risk of respiratory infections, a feed or supplement containing vitamin C may be helpful.
Other feed & management tips
Where possible, regular exercise may help to improve insulin sensitivity (reduced insulin sensitivity is a risk factor laminitis) and help maintain muscle tone/ topline.
Consider clipping horses and ponies with excessive hair growth.
A heavy worm burden can lead to weight loss in horses of all ages but seniors with PPID may have increased faecal egg counts and require more frequent monitoring and/ or treatment.
Check and refill water buckets regularly – remember horses and ponies with PPID may drink more.
We generally recommend access to an equine salt lick for all horses and ponies but those sweating regularly may need additional electrolytes. Table salt (the same salt you put on your chips) is generally an effective solution but for specific advice, contact the Care-Line.