Feeding a Horse with Cushing's Disease (PPID): A Complete Guide

A diagnosis of Cushing's disease — or more accurately, Pituitary Pars Intermedia Dysfunction (PPID) — can feel overwhelming. You're suddenly navigating medication schedules, blood tests, and a long list of dietary dos and don'ts. But here's the good news: with the right feeding strategy, horses with PPID can live comfortable, active lives well into their twenties and beyond.

This guide walks you through everything you need to know about feeding a horse with Cushing's disease, from understanding the condition to building a practical, balanced diet.

What Is Cushing's Disease (PPID)?

PPID is a progressive neurodegenerative condition affecting the pituitary gland at the base of the brain. It most commonly develops in horses over 15 years old, though younger horses can be affected. The pituitary gland overproduces a hormone called ACTH, which in turn leads to elevated cortisol levels and a cascade of metabolic disruptions.

Common Signs of PPID

• A long, curly coat that fails to shed (hirsutism)
• Muscle wasting, especially along the topline
• Fat redistribution — often a cresty neck or fat pads above the eyes
• Increased thirst and urination
• Recurrent laminitis
• Delayed wound healing
• Lethargy and poor performance
• Increased susceptibility to infections

While medication (typically pergolide) is the cornerstone of treatment, diet plays a critical and often underestimated role in managing PPID effectively.

Why Diet Is So Important for Horses with PPID

Many horses with Cushing's disease also have insulin dysregulation (ID), sometimes called equine metabolic syndrome (EMS). This means their bodies struggle to manage blood sugar levels properly. When a horse with PPID and insulin dysregulation eats a meal high in sugar and starch, blood glucose spikes, insulin surges, and the risk of laminitis skyrockets.

Laminitis is the single biggest threat to the welfare and life of a horse with PPID. And laminitis risk is directly influenced by what goes into the feed bucket. That's why getting the diet right isn't optional — it's essential.

The Golden Rule: Low Sugar and Starch

The most important dietary principle for a horse with Cushing's disease is to keep the combined sugar and starch content — often referred to as non-structural carbohydrates (NSC) — below 10% of the total diet on a dry matter basis.

This single rule shapes every feeding decision you'll make, from forage selection to bucket feed choices.

What Counts as Sugar and Starch?

• Water-soluble carbohydrates (WSC): Simple sugars and fructans found in grass and hay
• Starch: Found in cereal grains like oats, barley, and maize
• NSC = WSC + Starch (this is the figure you're aiming to keep below 10%)

Forage: The Foundation of a PPID Diet

Forage should make up the vast majority of your horse's diet — ideally 1.5% to 2% of their body weight per day. For a 500 kg horse, that's 7.5 to 10 kg of forage daily (on a dry matter basis).

Choosing the Right Hay

Not all hay is suitable for a horse with Cushing's disease. The sugar content of hay varies enormously depending on grass species, time of cutting, weather conditions, and maturity at harvest.

The only reliable way to know the NSC content of your hay is to have it tested. Visual appearance and smell tell you nothing about sugar levels.

Look for hay with:

• WSC + starch below 10% on a dry matter basis
• Moderate protein (8–12%)
• Good hygiene — no mould or dust

Soaking Hay to Reduce Sugar

If your hay tests above 10% NSC, soaking can help reduce sugar content. Here's how:

• Soak in cold water for 8–12 hours, or in warm water for 30–60 minutes
• Soaking can reduce WSC by 20–50%, though results are variable
• Always drain and discard the soak water — it's full of dissolved sugars
• Feed soaked hay within a few hours to prevent fermentation, especially in warm weather

Important: Soaking also leaches minerals, so you'll need to compensate with a suitable vitamin and mineral supplement.

Hay Replacers

If you cannot source low-sugar hay, consider commercially available low-NSC hay replacers such as:

• Unmolassed sugar beet pulp (soaked)
• Short-chopped fibre feeds specifically formulated for metabolic horses
• Hay cubes or pellets made from tested, low-sugar forage

Always check the guaranteed analysis on the bag and confirm the NSC content is below 10%.

Managing Grazing

Fresh grass is one of the biggest dietary risks for a horse with PPID. Pasture grass can contain NSC levels well above 20–30%, particularly during:

• Spring growth flushes
• Sunny afternoons (sugars peak in late afternoon)
• Cool nights followed by sunny days
• Autumn, when fructan levels can spike
• Drought-stressed or frost-stressed grass

Strategies for Safer Grazing

• Use a grazing muzzle to reduce intake by approximately 30–80%
• Restrict grazing to early morning (before 10 am) when sugar levels are typically lowest
• Create a track system or bare paddock to limit grass access
• Strip graze small areas to control intake
• In high-risk periods, remove pasture access entirely and feed tested hay instead

For horses with a history of laminitis or confirmed insulin dysregulation, some veterinary nutritionists recommend no grazing at all. Discuss this with your vet.

What to Feed in the Bucket

Many traditional horse feeds — mixes, coarse feeds, and cereal-based products — are far too high in sugar and starch for a horse with PPID. Here's what to look for and what to avoid.

Feeds to Avoid

• Cereal grains: oats, barley, maize, wheat
• Molassed feeds and chaffs
• High-starch competition or conditioning feeds
• Treats containing sugar: mints, apples, carrots in large quantities
• Molasses and treacle-based licks

Suitable Feeds

• Unmolassed sugar beet pulp — an excellent fibre source, low in NSC when unmolassed. Always soak thoroughly before feeding.
• Low-NSC commercial feeds — several feed companies produce feeds specifically designed for horses with PPID/EMS. Look for products with NSC below 10%.
• Oil — for horses that need additional calories without sugar, adding vegetable oil (such as linseed oil or soya oil) provides energy from fat. Start with small amounts and build up to a maximum of around 100 ml per 100 kg of body weight per day.
• Unmolassed chaff — check the label carefully, as some "lite" or "low-calorie" chaffs still contain added molasses.
• Soaked grass pellets or cubes — if tested or guaranteed to be below 10% NSC.

Vitamins, Minerals, and Supplements

Horses with PPID often have increased nutritional demands, and soaked hay further depletes mineral content. Supplementation isn't a luxury — it's a necessity.

Essential Nutrients to Focus On

• Vitamin E: A powerful antioxidant that supports immune function and muscle health. Horses on hay-only diets are almost always deficient. Aim for 1,000–2,000 IU per day (natural vitamin E is better absorbed).
• Magnesium: Plays a role in insulin sensitivity. Many PPID diets benefit from additional magnesium.
• Zinc and Copper: Critical for hoof health, immune function, and coat quality. Often deficient in UK and European forages.
• Selenium: Important for antioxidant defence, but toxic in excess. Test your forage or consult a nutritionist before supplementing.
• Chromium: Some evidence suggests chromium may support insulin regulation, though research is ongoing.
• Omega-3 fatty acids: Found in linseed (flaxseed) oil, these have anti-inflammatory properties that may benefit horses with chronic inflammation.

Choosing a Supplement

Look for a low-sugar, low-starch vitamin and mineral supplement or balancer specifically designed for horses with metabolic conditions. Avoid balancers that contain cereal grains or molasses as carrier ingredients.

If you're unsure whether your horse's diet is meeting nutritional requirements, analysing your horse's diet with a tool like MyEquiBalance can help you identify gaps and avoid over- or under-supplementing.

Feeding the Underweight PPID Horse

Muscle wasting and weight loss are common in advanced PPID, and it can be genuinely challenging to keep weight on these horses without resorting to high-starch feeds.

Safe Calorie-Boosting Strategies

1. Increase forage quantity — if your horse can eat more hay, this is the safest way to add calories
2. Add oil — calorie-dense and low in NSC. Linseed oil is a good choice.
3. Feed unmolassed sugar beet pulp — high in digestible fibre and well-tolerated
4. Consider a high-fat, high-fibre commercial feed — several are available with NSC below 10%
5. Add quality protein — older horses often need more protein to maintain muscle. Look for feeds or supplements containing lysine, methionine, and threonine — the key amino acids for muscle synthesis.
6. Split meals into smaller, more frequent feeds — this aids digestion and helps maintain steadier blood glucose levels

When Weight Loss Won't Stop

If your horse continues to lose weight despite dietary adjustments, revisit the pergolide dose with your vet. Uncontrolled PPID is often the underlying cause of persistent weight loss. Dental issues, which are common in older horses, should also be investigated — a horse that can't chew properly won't extract full nutrition from forage.

Feeding the Overweight PPID Horse

Some PPID horses carry excess weight, particularly those with concurrent EMS. Obesity worsens insulin dysregulation, so achieving a healthy body condition score (ideally 4.5–5 out of 9) is important.

Weight Loss Tips

• Restrict total forage intake to 1.5% of body weight per day (dry matter basis), but never feed less than 1.25% — going too low increases the risk of gastric ulcers and stereotypic behaviours
• Use small-hole haynets or slow feeders to extend eating time
• Eliminate all unnecessary bucket feeds — if the forage is balanced with a suitable supplement, many overweight PPID horses don't need bucket feed at all
• Increase exercise gradually if the horse is sound — even gentle walking helps improve insulin sensitivity
• Monitor body condition regularly, aiming for slow, steady weight loss

Seasonal Considerations

PPID has a seasonal pattern. ACTH levels naturally rise in autumn, which means horses with PPID are often at their most vulnerable in late summer and autumn. This is also a time when pasture fructan levels can spike.

Autumn Checklist

• Discuss a potential pergolide dose increase with your vet ahead of autumn
• Tighten grazing restrictions from late August onward
• Monitor closely for signs of laminitis — increased digital pulses, shifting weight, reluctance to walk
• Recheck ACTH levels as recommended by your vet

Sample Daily Diet for a 500 kg PPID Horse (Good Weight)

Here's an example of what a balanced PPID-friendly diet might look like. This is a starting point — individual horses vary and every diet should be tailored.

Grass access: Restricted or managed with grazing muzzle, depending on the season and pasture NSC levels.

Working with Your Vet and Nutritionist

Feeding a horse with PPID is not a one-size-fits-all exercise. The best outcomes come from a team approach:

• Your vet manages medication, monitors ACTH and insulin levels, and oversees overall health
• A qualified equine nutritionist can formulate a balanced, safe diet tailored to your horse's specific needs and available forage
• You are the daily observer — noticing subtle changes in weight, energy, coat, and comfort that guide adjustments over time

Don't be afraid to ask questions, request forage analysis, and revisit the diet as your horse's needs change with age and season.

Key Takeaways

• Keep total dietary NSC (sugar + starch) below 10% on a dry matter basis
• Test your hay — it's the single most valuable thing you can do
• Manage grazing carefully, especially in spring and autumn
• Supplement vitamins and minerals, particularly when feeding soaked hay
• Prioritise fibre and fat as energy sources over cereals and grains
• Work with your vet to optimise pergolide dosing alongside dietary management
• Monitor body condition, digital pulses, and overall wellbeing regularly

With thoughtful feeding and good veterinary care, a Cushing's diagnosis doesn't have to mean the end of a horse's quality of life. Many PPID horses thrive for years with the right management — and diet is one of the most powerful tools you have.