Mac and Me

Understanding KPU in Horses – A Guide for Equestrians

Kryptopyrroluria

If you have come across the term KPU (Kryptopyrroluria) for the first time, you might be wondering what it means, whether your horse could have it, and why you have never heard your vet mention it before.

This page is designed to give you a clear, practical introduction along with a checklist you can use to help decide whether further investigation is worthwhile.

What is KPU?

KPU (Kryptopyrroluria) is not a disease but a metabolic detoxification disorder. It occurs when the body’s normal toxin elimination pathways, especially those involving the liver and hindgut, are compromised.

At the root of the problem is usually a disturbed hindgut microbiome. In a healthy horse, fibre-fermenting gut bacteria produce vital, activated nutrients such as Pyridoxal-5-Phosphate (P5P), the active form of vitamin B6, which the liver needs to neutralise and eliminate toxins.

When the microbiome is disrupted through diet, stress, illness or toxin exposure, the liver cannot complete detoxification. Instead, toxins bind to important trace minerals like zinc, selenium and sulfur, leading to deficiencies and a wide range of possible symptoms.

The Disease of a Thousand Faces

KPU is sometimes referred to as the disease of a thousand faces because of the bewilderingly wide range of symptoms it can cause. Horses with KPU may show a mix of seemingly unrelated problems which can change over time. This is one of the reasons it is so often misdiagnosed, or each symptom is treated separately without identifying the underlying cause.

In some cases, KPU may be the hidden driver behind symptoms that are also linked with conditions such as PSSM2/MIM. Addressing KPU can, in turn, help resolve those symptoms.

Common Signs of KPU in Horses

According to equine practitioners familiar with KPU protocols symptoms can include:

  • Faecal water syndrome or chronic diarrhoea
  • Poor muscle development and topline despite adequate nutrition
  • Persistent mud fever or pastern dermatitis
  • Seasonal or year-round itching
  • Unexplained laminitis
  • Chronic cough, nasal discharge or allergies
  • Repeated tendon or ligament injuries
  • Slow recovery after work
  • Low stamina and fatigue

KPU in Horses – Diagnosis Checklist

This checklist is designed to help you and your vet decide whether testing for KPU might be worthwhile.
KPU can present with a wide range of symptoms, so not every horse will display all of these.

Step 1 – Symptom Patterns

General Health & Performance

  • Fatigue or poor stamina despite regular work
  • Slow recovery after exercise
  • Poor topline despite adequate nutrition
  • Difficulty building muscle

Digestive Issues

  • Faecal water syndrome
  • Chronic diarrhoea or intermittent loose droppings
  • Recurrent mild colic symptoms
  • Poor appetite or fussy eating

Skin & Coat

  • Mud fever / pastern dermatitis
  • Persistent or seasonal itching
  • Dull coat or slow coat changes
  • Recurrent skin infections

Hoof & Limb Health

  • Laminitis (especially repeated or unexplained episodes)
  • Tendon or ligament problems without obvious injury
  • Slow healing of injuries

Respiratory & Immune

  • Chronic cough or nasal discharge
  • Recurrent infections
  • Allergies or hypersensitivities

Step 2 – History & Risk Factors

  • Long-term haylage feeding or structured chaff diets
  • Previous severe illness or long antibiotic use
  • Known hindgut acidosis or imbalanced microbiome
  • High stress levels or frequent travel
  • History of toxin exposure (mouldy forage, contaminated water, certain pasture plants)

Step 3 – Veterinary Blood Work Indicators

(Discuss with your vet – not for self-diagnosis)

  • Low-normal red blood cell count or haemoglobin
  • Low serum zinc and/or selenium
  • Altered liver enzyme values
  • Possible low albumin or total protein

Download the KPU in horses PDF checklist https://macandme.blog/wp-content/uploads/2025/08/kpu_horses_diagnosis_checklist.pdf

Important UK Context

In the UK, many equine vets are not yet familiar with or supportive of KPU as a recognised condition. This can make it challenging to get targeted testing or protocol guidance through your regular veterinary practice. If your vet is unfamiliar with KPU, you may need to work alongside an experienced practitioner who can interpret results and provide a tailored support plan, while keeping your vet informed.

Next Steps if You Suspect KPU

  1. Consult your vet about a KPU-specific blood test panel.
  2. If needed, seek a practitioner experienced in KPU protocols who can work alongside your vet.
  3. Begin gut-liver support and micronutrient replenishment under professional guidance.

References & Further Reading