Horse Side Vet Guide ®

Equine Health Resource

Hay looks Old, Dusty or Moldy

Code Green - Contact Your Vet to Obtain Useful Advice & Resources

Code Green - Contact Your Vet to Obtain Useful Advice & Resources

  • To discuss your equine's general health and management.

Horses are uniquely sensitive to changes in feed, especially changes in hay. For this reason, do not feed hay of questionable quality or hay that looks old, dusty or moldy. Set it aside for examination or discard it.

If your horse has eaten poor quality hay, monitor them for signs of intestinal or respiratory distress. Look out for signs of abdominal pain (colic). Listen for coughing.

Over the long term, the feeding of dusty hay can create irreversible changes in the horse’s lungs and the development of RAO (formerly COPD, heaves). In addition, bouts of life-threatening respiratory distress (similar to an asthma attack) can occur.


Monitor your horse during any transition to a new hay, and for several days (even weeks) afterwards. If your horse is coughing, or showing any signs of illness or disease, stop feeding the hay.

Perform the Whole Horse Exam (WHE), paying particular attention to respiratory rate and effort, and the presence of coughing. Contact your vet and share your findings and concerns. Save representative samples of the hay for assessment and analysis.

Author: Doug Thal DVM Dipl. ABVP


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