Horse Side Vet Guide ®

Equine Health Resource

Manure has Sour or Abnormal Odor

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 rely on a massive population of gastrointestinal microorganisms that break down complex carbohydrates into useable energy. Digestive upsets and changes in the ecology of the intestinal tract can make manure smell sour or strange. Horses with intestinal conditions that alter the bacterial flora have marked changes in the smell of their manure.

Depending upon the severity and nature of the disturbance to the gut, this change in smell may correspond with changes in the color and consistency of the manure. Because the colon is such a massive organ and a critical part of a horse’s physiology, changes to manure must be taken seriously. Diseases of the colon can quickly become life-threatening.


Assess your horse’s general health using the Whole Horse Exam (WHE). Evaluate their feed and manure. Is the hay moldy or weedy? Examine your other horses’ manure for similar changes. Share your findings and concerns with your vet.


Taken alone, with no other sign of illness or disease, your vet may advise you to simply monitor the situation. However, your vet may want to evaluate your horse if they are exhibiting signs of other problems, however subtle. Keep in mind that diarrhea in the adult horse is considered a veterinary emergency.

Author: Doug Thal DVM Dipl. ABVP


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