Hind Gut Ulcers

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

About Dr. Kellon

Graduate of University of Pennsylvania Veterinary School. Owner of Equine Nutritional Solutions, www.drkellon.com, industry and private nutritional consultations, online nutritional courses. Staff Veterinary Expert at Uckele Health and Nutrition https://tinyurl.com/vdxfex5h .
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21 Responses to Hind Gut Ulcers

  1. Pingback: Treating Hindgut Ulcers - Equine Gastric Ulcers

  2. Yvonne Gale says:

    Very interesting article, I wonder if the discomfort some horses are having is through an intolerance to something. My grandson had no diarrhoea but suffered bad pains, we removed gluten and he is now 98% better. My mare is clearly uncomfortable right flanks which causes her to tense up and have particularly neck muscle problems, it tends to be spring summer related, overies etc in very healthy state and no antibodies to tapeworm and neg worm count. Her droppings tend to be loosish but a little dry bran makes them normal. She had one test which showed occult blood recently when she was very loose but more recently normal test. She has been diagnosed a year or so ago with gastric ulcers and went on a course of gastrogard then rescoped and they had cleared. She is very much a herd mare and one that is very aware of her predators. She does have a couple of other issues, medial meniscal injury to right stifle and kissing spine. But with lots of rehab she has been going excellently until a few weeks ago. She is a perfectly behaved mare, with a lovely pleasing temperament so it is sad to see her uncomfortable at times. She is mainly on hay diet, light chaff, handful of fibre nuts and a balancer twice a day with 30 ml of flaxseed oil and a joint supplement. Any ideas ?? Yvonne


    • uckeleequine says:

      Thank you for all the details. It helps to illustrate how complex it can be to diagnose from signs/symptoms alone. Horses certainly can have food intolerances. They are of two general types. One would be a true “allergy” like reaction like gluten sensitivity. The other would be foods that the bacterial population in the hind gut cannot ferment well. In true allergy/sensitivity, it is the small intestine which is inflamed. If that is detectable by sensitivity in the overlying skin it would be in the left flank. Disorders of fermentation, either poor fiber fermentation (fairly common in older horses) or abrupt diet change with presentation of unaccustomed food materials (including grass), involves the large intestine. The right flank contains the cecum, the first part of the large intestine, but the left flank also contains many loops of colon. Bloating/distention of both flanks would be expected except in a situation of right displacement of the colon, a type of colic that often requires surgery. Inflammation of the cecum only (called typhilitis) is extremely rare. Unless the right flank sensitivity always correlates with presence of loose manure and manure is normal when right flank is not as touchy it’s difficult to make a case for her flank sensitivity having a GI origin. However, it is also important to recognize that most horses are more sensitive to touch on the right side than the left, especially around the hindquarters, simply because we do more with them from the left side (e.g. applying tack or blankets, mounting, etc.). Therefore, flare up of back or stifle pain that makes her generally more anxious and apprehensive with sensitivity to touch may seem worse on the right side, may actually be worse on the right in her case because of the stifle injury. I would suggest a complete veterinary examination, not just focusing on the intestinal tract, when she is having one of these episodes. If this results in the intestinal tract indeed being the likely focus, try to identify anything that has changed in her diet, including grass, and put her back on a feeding routine that she previously tolerated well. Also important to realize that immature forms of Strongyles which are not laying eggs are the most likely to cause symptoms.


      • Yvonne Gale says:

        Thank you for your reply, interesting and helpful. She is very complicated. Her sensitivity on her right flanks is not there all the time, when it is she doesn’t like even grooming on the right side and is fairly grumpy with the touch on her right side. When the vet came yesterday she was considerably better, apart from sore muscle over C3 on left side of neck. She was 1/10 lame on left hind and 2/10 after flexion. Interestingly today her muscle felt much better, she was definitely in season but was very tired. She was also vaccinated yesterday and so after light work and 5 min rest followed by bit of spooky behaviour had an extremely fast respiration rate which took about 5 minutes to subside to a fast rate and then another 5 to normal but remained very tired looking. Then at end of day droppings were loose. She does have times of bloating, and also appearance of slight colics, mainly overactive gut sounds and on another occasion sweating on belly. I have watched her on cctv overnight in the past showing clear signs of being uncomftable. She has had two episodes of colic that need treating in the last 18 months.Her diet has not changed at all for some time, her field is poor grass. She does well over the average amount of droppings a day. I only say all this as she has displayed signs of GI problems from time to time. I just can’t help wondering whether to really look into a change of diet. She is on ad lib hay which is soaked because of her ulcer history and her body condition is perfect. I was also wondering about having a blood test for PPID or EMS. Yvonne


  3. Sandra says:

    I have a horse that was diagnosed by my vet as having hindgut ulcers so this is making me think all of the vets are just trying to get money.


  4. Jo-Claire says:

    How does Bute get better than kill prices? Are you referring to the kill pen/broker lots? Masking lame horses as sound?


  5. paulinewhitaker says:

    My friends ID X Has had diarrhoer for at least 10 years the only medication she has that works is codeine she has had intensive investigation but nothing changes this messy situation
    She is a quiet and calm mare
    Does not lose weight
    Now has cushings as well


  6. Paula says:

    My horse was just diagnosed with the Succeed test. She was not on phenylbutazone, was dewormed within the month with Equimax, is on daily Strongid, has a 12 % carbohydrate hay and balancing mineral supplement in soaked beet pulp for her daily ration. We use a pre and probiotic supplement. What else can cause hind-gut ulcers?


    • uckeleequine says:

      First, your horse was not diagnosed by the Succeed test with hind gut ulcers. She was diagnosed with the presence of trace blood; more specifically the proteins found in blood. In humans, the trace blood test is used to screen for malignancy/cancer. That’s a possibility here, but rare. Other potential causes include irritation to the bowel from ingestion of soil/”sand” or other foreign bodies, presence of an enterolith. Deworming may also trigger emergence of encysted life stages of small strongyles which would also give a positive.

      Dr. Kellon


  7. Ange says:

    My understanding of the effect of ‘bute’ is that it somehow affects PGE2 levels and so in turn reduces mucosal production, leaving the gut wall vulnerable to damage. I’ve also read that raised ACTH has a similar effect on PGE2, so I was wondering what your thoughts are on this – could conditions such as PPID be causative for such things as colitis, or are the things I’ve mentioned here wrong, or the mechanisms different?
    (I have a horse that was diagnosed from scoping with Pyloric EGUS and it took months to clear, only seeming to respond fully to treatment after PPID was diagnosed following laminitis and Prascend was started – she is still very ‘gut sensitive’ and I do feed different supplements such as YeaSacc to try to help her.). Many thanks!


    • uckeleequine says:

      You’re correct that phenylbutazone blocks PGE2 (prostaglandin), a “defense” response that leads to protective mucus. ACTH does not have this effect. PPID is not associated with an increased incidence of colitis. It may indeed be involved though since horses with untreated PPID have decreased healing.



    • uckeleequine says:

      You’re correct that phenylbutazone blocks PGE2 (prostaglandin), a “defense” response that leads to protective mucus. ACTH does not have this effect. PPID is not associated with an increased incidence of colitis. It may indeed be involved though since horses with untreated PPID have decreased healing.



  8. Laura says:

    Than what would say a treatment would be for what you’re calling this. I didn’t see any of that in there.


  9. Reblogged this on the whole horse blog and commented:
    Hind gut ulcers..


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