At some point, horse owners may be faced with a horse that eats manure. This is also known as “coprophagy,” which is Latin for eating feces.

For foals and young horses, manure-eating can be natural and expected. However, for adult horses, the eating of manure can be indicative of problems.

Young horses, by nature, are inquisitive. They tend to mimic their mothers and explore their environments, which may include their dam’s feces. The main reason, thought by many scientists, why foals eat manure is to help populate their hind gut with important digestive microbes. At birth, their digestive system is void of any digestive microbes that are critical in breaking down forage and other feed. Some also suggest the eating of manure helps stimulate the young horse’s immune system and is seen as beneficial. The only concern for foals and young horses when eating manure is getting infected with internal parasites. Thus, broodmares should be checked and dewormed as necessary in the weeks leading up to birth. Young horses may be individually dewormed beginning at 2 to 3 months of age.

Likewise, for adult horses, the ingestion of manure is rather harmless. Again, a major concern would be the potential spread of internal parasites. This is especially true of a horse eating manure from another horse. Yet, manure eating is not a normal behavior and can indicate problems in the horse’s diet or that they are suffering from stress and/or boredom.

A horse’s natural behavior is to eat forage all day. In fact, free-ranging horses may graze for upwards of 18 hours each day. With confinement, we have limited not only the hours horses are busy grazing, we also limit their forage intake. Studies have linked manure-eating in adult horses to those that are either underfed, or are fed diets that are low in fiber. This means horses that are not receiving enough roughage each day may start to eat feces to get the nutrients (i.e. fiber) that they are lacking.  This could also apply to horses that are kept on poor performing or maintained pastures. Thus, it is recommended adults horses receive at least 1.5% to 2.5% of their body weight per day in forage. For a 1000-pound horse, this would equal 15 to 25 pounds of quality forage each day. Other dietary considerations that may induce manure-eating in adult horses include:

  • High starch diets
  • Grazing on fresh, young pasture (low in fiber)
  • Low energy diets

A common question is whether manure consumption is the result of nutrient deficiencies. Outside of fiber, it would be rare for a nutrient deficiency to cause manure consumption. It is possible that manure may be consumed to meet protein needs in a horse on a very low protein diet; however, all but the lowest quality forages will provide sufficient crude protein (although limiting amino acids need to be supplied to complement forage crude protein). A lot of research has been devoted to understanding the impact and symptoms of vitamin and mineral deficiencies in the horse. Notably, coprophagy has not been identified as a symptom of deficiency in a single study where horses were intentionally fed diets designed to create nutrient deficiencies.

Another major cause to a horse suddenly ingesting manure is due to either stress or boredom. Again, since we have confined horses to stalls or paddocks, they are prone to developing abnormal behaviors often referred to as vices or stereotypies. These can include cribbing, wood chewing, eating of bark, or even tail rubbing. This could also include manure-eating. If a horse’s diet is ruled out as a cause of a vice, then it would be suggested to identify and minimize stress and find ways to alleviate boredom. Hay nets have begun to be recommended to lengthen the time a horse may spend eating their forage and this may be one strategy to eliminate boredom. Others have suggested adding either horse appropriate toys or design enrichment activities to keep a horse busy and active throughout the day.

Finally, sometimes horses are just weird.  If you have ruled out the causes for manure-eating, as outlined above, you can rest assured that it is a generally harmless habit. The major concern with any horse that eats manure is, of course, the spread of internal parasites. You can learn more about deworming your horses by reviewing our Deworming Rules for Your Horse article. Briefly, to treat your horse for parasites, it is recommended to first have a fecal float done to determine which, if any, parasites your horse may be infected with. If a parasite is identified, it would then be recommended to treat with the proper dewormer (anthelmintic). Due to increased parasitic resistance to many dewormers available today, it is no longer recommended to broadly treat a horse with a dewormer.
 

Nicole Rambo, Ph.D., Chris Mortensen, Ph.D.