What you see. The starting point for addressing any equine health related issue is your observation.


Manure has Sour or Abnormal Odor


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.

  • Code Green

    Contact Your Vet to Obtain Useful Advice & Resources
    • To discuss your equine's general health and management.

your role


What To Do

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.

your vet's role

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.
Questions Your Vet Might Ask:
  • Did the feeding or management change in the last 48 hours?
  • What, specifically, are you feeding?
  • Describe the type and quality of the hay?
  • What type of grain and how much grain are you feeding?
  • Do you think the horse's attitude and appetite are normal?
  • Has the horse received any medications or new feeds or supplements?
  • Does the horse have diarrhea or loose manure?
  • Are you feeding the horse alone or in a group?
  • What are the results of the Whole Horse Exam (WHE)?

Author: Doug Thal DVM Dipl. ABVP