Why Won't My Old Horse Shed His Coat?
A senior horse that won't shed a long winter coat is showing the classic red flag for PPID (Cushing's disease). Learn the signs, ACTH testing, pergolide, and management.
A senior horse that won't shed his winter coat is showing the single most recognizable sign of PPID, also known as Cushing's disease. The condition disrupts normal hormone signaling so the coat grows long, coarse, and sometimes curly and fails to shed on schedule. In any horse over about 15, a retained coat is a red flag that should prompt an ACTH blood test with your veterinarian, because PPID also carries a serious laminitis risk.
It can be easy to miss at first. Maybe the legs stay fuzzy a little longer than usual, or the horse looks scruffy in May while the herd is sleek. But a coat that does not shed properly in an older horse is rarely just cosmetic, and catching the cause early can prevent painful complications down the line.
Comfort and Coat Support for PPID Horses
Equine Veterinary Essentials Equine Metabolic Support
Herbal support marketed for PPID and insulin-resistant horses
Best Botanicals Chaste Tree Berry Powder
Herb traditionally used to support hormonal balance in horses
SmartEquine Smart & Simple Flax
Omega-3 flax to support coat and skin condition
These products support comfort and coat condition, but they are not a substitute for veterinary diagnosis and pergolide. Herbal metabolic supplements and chaste tree berry are popular with owners, yet evidence for them is limited, so use them as adjuncts and tell your vet what your horse is receiving.
What PPID Actually Is
PPID stands for pituitary pars intermedia dysfunction. In an aging horse, the part of the brain that normally keeps the pituitary gland in check degenerates, so the gland overproduces certain hormones. The result is a cascade of effects: a long, slow-to-shed coat (hypertrichosis), muscle loss over the topline, a pot-bellied look, increased drinking and urination, sluggish energy, a weakened immune system, and a heightened risk of laminitis. The disease is common, affecting a large share of horses over 15, and the longer it goes unmanaged, the more complications stack up.
The Coat Is the Tell
The retained coat is so distinctive that experienced vets and owners often suspect PPID on sight. Early on you may only notice longer hair along the legs, under the jaw, or a delayed and patchy shed. As the disease advances, the coat becomes long, coarse, and curly year round. Because the coat sign is visible from across the paddock, it is one of the most useful early warnings owners have.
Getting a Diagnosis
If your older horse is not shedding properly, ask your vet about an ACTH blood test. It is a simple draw that can usually be done during a routine visit. Because ACTH rises naturally in late summer and autumn, results are read against seasonal reference ranges, and a TRH stimulation test may be added for borderline cases. Many vets will also check insulin and glucose, since PPID and insulin dysregulation frequently travel together and that combination sharply raises laminitis risk.
| PPID Sign | What You Might See |
|---|---|
| Coat changes | Long, curly coat that sheds late or not at all |
| Muscle loss | Sunken topline, pot-bellied appearance |
| Drinking | Increased thirst and urination |
| Laminitis | Recurrent or unexplained foot soreness |
| Other | Lethargy, slow wound healing, recurrent infections |
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Treatment and Daily Management
PPID is managed rather than cured, but treatment is usually very effective. The cornerstone is pergolide (sold as Prascend), a once-daily tablet that restores more normal hormone signaling. Most horses begin shedding more normally, regain energy, and rebuild some muscle within a few months, and your vet will recheck ACTH to fine-tune the dose. Treatment continues for life.
Alongside medication, daily management matters. Keep the diet low in sugar and starch, built on tested or soaked forage and a ration balancer. Clip horses that cannot shed so they stay cool and comfortable. Stay current on dental floating, since PPID horses are prone to dental disease, and keep the farrier on a regular schedule to monitor for laminitis. Because the immune system is weakened, watch closely for slow-healing wounds, skin infections, and dental abscesses. For the complete picture, see our in-depth guide to PPID in senior horses and our overview of laminitis. With early diagnosis and steady management, a PPID horse can live comfortably for many more years.
Frequently Asked Questions
Why won't my old horse shed his winter coat?
A senior horse that holds a long, thick, or curly coat into late spring or summer is showing the single most recognizable sign of PPID (Cushing's disease). The condition disrupts normal hormone signaling so the coat fails to shed on schedule. Other causes include poor nutrition, heavy parasites, or chronic illness, but in an older horse a retained coat is a PPID red flag that warrants an ACTH blood test with your veterinarian.
Does a long coat always mean Cushing's?
Not always, but in a horse over about 15 it should put PPID at the top of the list. The classic picture is a long, coarse, sometimes wavy or curly coat (hypertrichosis) that sheds late, patchily, or not at all. Early PPID may show only delayed shedding along the legs or under the jaw. Poor body condition, lethargy, or repeated laminitis alongside a retained coat make PPID even more likely. A simple ACTH test confirms it.
How is PPID diagnosed in an older horse?
The standard screening test is a resting blood ACTH level, which your vet can draw on a routine visit. Because ACTH varies with the season, results are interpreted against seasonal reference ranges, and a TRH stimulation test may be used for borderline cases. Many vets test any senior horse with a delayed or abnormal coat, recurrent laminitis, muscle loss, or excessive drinking. Early diagnosis lets you start treatment before complications like laminitis develop.
Can PPID be treated?
Yes. PPID is managed, not cured, but treatment is usually very effective. The mainstay is pergolide (Prascend), a once-daily tablet that restores more normal hormone signaling. Most horses shed more normally, regain energy, and rebuild some muscle within a few months. Your vet will recheck ACTH to fine-tune the dose. Treatment is lifelong, and it is paired with a low-sugar diet, good dental and hoof care, and vigilant laminitis monitoring.
Should I body-clip a Cushing's horse that won't shed?
Often yes. A horse that cannot shed a heavy coat will overheat and sweat in warm weather, which leads to skin problems and discomfort. Body clipping keeps these horses cool and lets the skin breathe, and it makes it easier to spot weight loss or skin issues. Clip as the weather warms, and provide a light sheet on cool nights afterward. Clipping manages the symptom, but it does not replace treating the PPID itself.
Why do Cushing's horses get laminitis?
PPID is strongly linked to insulin dysregulation, and high circulating insulin damages the sensitive laminae that bond the hoof wall to the coffin bone, triggering laminitis. This endocrine laminitis can appear with little warning, which is why a retained coat is worth taking seriously. Managing PPID with pergolide, keeping the diet low in sugar and starch, maintaining a healthy weight, and staying on top of farrier care all reduce the risk.
What diet is best for a horse with PPID?
Most PPID horses do well on a low-sugar, low-starch diet built on good forage, ideally hay tested or soaked to lower its sugar content, plus a ration balancer to fill vitamin and mineral gaps without excess calories. Avoid sweet feeds and grain-based concentrates. Thin or hard-keeping PPID horses can have safe calories added with beet pulp or oil. Always coordinate the diet with your vet, especially if the horse has had laminitis.
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