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Hereditary equine regional dermal asthenia (HERDA)

Quick facts

  • HERDA is a genetic disease in quarter horses and appaloosas, especially cutting horses.

  • Signs of HERDA include stretchy skin, severe skin wounds and scarring along the back and withers.

  • The American Quarter Horse Association requires all breeding stallions be tested for HERDA.

  • There is no cure or treatment for horses with HERDA.

What is HERDA?

Stretchy, elastic skin
Horses with HERDA have stretchy, elastic skin. Photo credit: Danika Bannasch, UC Davis

Hereditary equine regional dermal asthenia (HERDA) is a genetic skin disease in quarter horses and appaloosas. Signs of HERDA include:

  • Stretchy, elastic skin

  • Sloughing skin

  • Severe skin wounds

  • Scarring along the back and withers

These signs often appear in 1- to 3-year-old horses, when saddling starts.

How common is HERDA?

HERDA is more common among cutting horses, specifically from the Poco Bueno line. About 2.5 to 3.8 percent of quarter horses carry the gene linked to HERDA. Between 14.2 and 28 percent of these horses are cutting horses.

Diagnosis and testing

Skin tests can detect HERDA in suspected horses.

As of 2015, the American Quarter Horse Association requires all breeding stallions be genetically tested for HERDA. The Veterinary Genetics Laboratory at the University of California Davis can run a five-panel test. This test can identify normal, affected and carrier horses. A horse must have two copies of the gene linked to HERDA to be affected.

These tests can help breeders make sound breeding choices and reduce the rate of HERDA in the quarter horse population.


There’s no cure or effective treatment for HERDA. Horses with HERDA are unusable for performance and as a result, owners often have them put down.

Authors: Nichol Schultz, DVM, former graduate student, College of Veterinary Medicine and Molly McCue, DVM

Reviewed in 2021

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