It’s difficult to go anywhere online (and probably off) where people are talking about horses without having something come up about hind gut ulcers, symptoms and treatments. There are even commercial supplements out there, including from companies run by people who should know better. There is no such thing as ‘hindgut ulcer syndrome’ that is a correlate of gastric ulcer syndrome and certainly no cause that a supplement would correctly treat.
Tapeworms are a common cause of hindgut ulcers
It is not unusual today to hear people claiming that 60 to 65% of horses have hind gut ulcers. However, if you read medicine, surgery and pathology textbooks or the published literature there is no mention of this widespread hindgut ulcer disease. It isn’t even mentioned in the horse health articles for owners on the AAEP.org web site.
When ulceration (an open sore or erosion in the lining of the intestine) occurs it is inevitably linked to tapeworm (or bots in the stomach) attachment sites, migration and emergence of small or large Strongyle larvae, or exposure of the lining to NSAIDs, usually phenylbutazone, or some caustic substance like arsenic.
Severe inflammation secondary to pathogenic bacteria or extreme acidosis caused by grain overload or massive doses of pure fructan can also cause this but the entire lining of the organ is compromised and such horses are obviously very ill with fever, colic, diarrhea, sepsis and laminitis. Another potential but relatively rare cause of inflammation and erosion is autoimmune bowel disease.
You may read that this breakthrough finding of widespread colonic ulceration was made during a university autopsy study. In fact, it was a cursory inspection of the digestive tracts in a slaughter house by the owner of a supplement company. Any abnormality of the lining, regardless of size, depth, appearance, etc. was called an “ulcer”.
No history was available on the horses, including phenylbutazone use, but it is well known that large doses are routinely used in slaughter horses in hopes of making the horses sound enough to bring better than killer price. No deworming history. No diet history. All horses below a certain age were called “performance horses” regardless of breed and lack of history. Presence of parasites was not recorded. No blood tests for drugs. No cultures for pathogenic bacteria. No pH/acidity testing. No microscopic sections (helpful because cell types give clues as to cause). No pathologist.
Intricately woven into this story of hind gut ulcers is the idea of colonic acidosis. As above, feeding very large amounts of grain or pure fructan can cause a cecal acidosis severe enough to damage the intestinal lining but it is also true you can feed as much as 6 lbs of whole barley, whose starch is poorly digested and passes into the large intestine, with no change in pH or digestive upset. As a general rule, pH has to get below 6 to cause damage to the intestinal lining as detected by increased bacterial products circulating in the blood. However, feeding as much as 13 lbs of sweet feed does not decrease pH below 6. In the fructan overload model the pH was below 4.
All horses with overload of rapidly fermentable, lactate yielding, carbohydrate in their hind gut have at the very least obvious “cow plop” diarrhea and are off feed.
Despite all this, even horses on predominantly or entirely hay diets are being diagnosed with hind gut ulcers based on vague and totally nonspecific symptoms such as not liking their flanks touched or dragging their toes. They are being treated with the goal of neutralizing acidity in their hind gut. Some are even given medications used to stop acid secretion in the stomach despite the fact there are no acid secreting cells in the hind gut. One extremely pricey supplement contains only low doses of ingredients that would be digested and absorbed before they reached the hind gut.
Disturbances of the hind gut/large intestine definitely exist but the correct treatment is to find the cause and correct it. Hind gut ulcers is not a real disease.
Eleanor Kellon, VMD