Is there an effect of diet on glandular ulcers?

Review of Effect of diet composition on glandular gastric disease in horses

My ears pricked when I received an email alert about a study that had just been published “Effect of diet composition on glandular gastric disease in horses”. That’s because up until recently, we’d thought that glandular disease risk factors were management and stress related, and diet didn’t really play a role. Of course, I needed to know more, with mounting evidence that diet may indeed play a role in glandular disease in some horses.

This particular study looked at the effect on glandular scores of substituting half of the grain concentrates in the diet with alfalfa pellets. Those which remained on the full rate of grain concentrate in their diets were called the Control group and those receiving half grain concentrate and half alfalfa were called the Alfalfa group. Trainers were instructed to feed their horses the same diet for 4 weeks prior to the study commencing (Day 0) – the before diet was the same as the Control diet.

Summary of findings were:

  • When comparing the Control and Alfalfa diet groups, no difference in the number of horses with glandular ulcers were found between the two groups.
  • Within the Control group, the number of horses with a glandular score ≥2 increased over the study period.
  • In the Control group, horses that had a glandular scores 2-4 at the beginning, did not show any improvement over the study period.
  • In the Alfalfa group, 5 out of 6 horses that had glandular scores 2-4 at the beginning of the study, showed improvement in their glandular scores (improved from ≥2 to 0-1).

This is where things took an unexpected and interesting turn. The researchers compared the non-ulcerated horse group (glandular scores 0-1) with ulcerated horse group (glandular scores ≥2) at Day 0. They found that simple sugar intake of the diet these horses were on before Day 0 was significantly different between these two groups. I know what you’re thinking…high sugars blah blah blah…but no! When comparing many variables including diet, the non-ulcerated group had a significantly higher daily intake of simple sugars in their before Day 0 diets, compared with the ulcerated group.

The researchers thought that higher daily intake of simple sugars which supports certain strains of Lactobacillus may have a protective effect in the stomach. Lactobacilli adhere to the gastric mucosa, forming biofilms and outcompeting pathogenic bacteria. This has been explored in rat models and supports the theory proposed by the authors.

Looking at the effect of substituting half the concentrate grain ration with alfalfa pellets, a positive effect was seen, with fewer horses with GGD at Day 42. The authors propose that this may be the results of a reduced amount of starch available to starch-utilising bacteria in the stomach. These starch-utilising bacteria produce fermentation products which change the pH of the stomach content, which cause other short chain fatty acids such as butyric acid to be more harmful, resulting in mucosal damage. The authors also add that alfalfa pellets offer a buffering effect within the stomach and can contribute to maintaining a higher pH despite acid secretions of strong fermentations associated with grain meals.

Key takeaways-

    1. Some Lactobacillus strains may have a protective effect in the stomach, reducing glandular disease and accelerating healing of existing glandular lesions.
    2. Reducing starch in diets is beneficial to reducing the fermentation products in the gastric contents, which otherwise when combined with very acidic environment cause damage to the glandular mucosa.
    3. Inclusion of alfalfa (lucerne) pellets with grain concentrate can provide a buffering effect within the stomach to maintain a higher pH, reducing harmful effects of short chain fatty acids on gastric mucosa.

Many interesting findings! If you’d like to know the nitty gritty details or read the full article, it is available open access at:



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Spotty’s Glandular Ulcers Have Healed!

Back in May last year we scoped our new pony Spotty and found she had mild glandular ulcers. The only risk factor we could ‘see’ was the fact she had been a chronic ‘sweet itch’ pony for years. You can read the backstory here

Our dilemma at the time of scoping was she had already been with us for 2 months, on a balanced diet, including a gut supplement because I was suspicious of ulcers and with constant access to fibrous pasture.

So what we didn’t know was were these ‘mild’ ulcers healing and on their way out? OR were they persistent (like Galaxy’s) and will remain despite her new diet and the removal of her source of chromic stress (no midges at my place and therefore no itching).

At the time, in consultation with my vet, we chose to not medicate Spotty and rescope. Due to Covid lockdowns, the next rescope we could do was 6 months later… in late November 2021.

In the period between May and November her picky eating disappeared, she was happily eating salt and while her stubbornness didn’t disappear under saddle she certainly was content being ridden when she was doing something that didn’t involve repetition (hates being ridden in an arena!).

What the scope showed us

And I am RELIEVED to report that for Spotty, on re-scoping, her glandular ulcers had resolved!!  After the experience with Galaxy (who was scoped first on the same day) my heart was in my mouth when Spotty was being done, so I was beyond relieved to find her glandular stomach in excellent shape!

She did have some hyperkeratosis (Grade 1 squamous ulcers)… sigh. I expect this was due to her grazing being restricted via strip grazing in the 2 months prior to the scoping and the grazing she did have access to was very lush!

My suspicion is that with just lush, watery pasture in the mornings as I moved their strip grazing fence and lucerne/alfalfa hay once a day in the late afternoon there is long periods of time where there is unlikely to be protective fibre in the stomach.

AND they probably don’t produce much saliva when eating lush pasture. There is at least one study (Bell et al 2007) that shows in racehorses that time at pasture was not protective against ulcers.

Next steps…

My plan is to provide access to straw next spring to make sure they always have something fibrous to chew on without blowing their calorie budget!

Fast forward to now though (late summer), Spotty is now living on a giant track with her pasture buddies Poet and Popcorn. They have lots of low quality, fibrous pasture to munch on all day and they get new pasture in a strip graze paddock right at the end of their track each day. So fingers crossed her squamous region is doing better.

She certainly looks good on the outside, but as Galaxy has so beautifully shown us, this is NOT an indicator of internal stomach health!



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Meet Spotty: A Case Study in Ulcers

Here is an interesting little case for you!

Meet Spotty… who isn’t spotty … her full name is Spotlight!

Spotty has just joined our little herd of equines and has fitted in beautifully with Popcorn and Poet.

I bought her from a friend who wanted to sell her as she was a chronic ‘QLD Itch’ (sweet itch) pony and my friend wanted her to go somewhere with no midges!

I was looking for a pony and she is just perfect for us. And we have no midges!

What is interesting about this you ask… nothing, yet!

BUT, the first few times I fed Spotty I noticed she was pretty finicky. For a pony she was also in excellent (not fat) condition, despite having had free access to pasture. AND if I added salt to her feed she wouldn’t eat it.

Plus she could be a little grouchy when getting saddled up and is a bit hesitant to go forward some days, (which yes, could be just her being a pony who knows she can beat her inexperienced rider, but for now I have given her the benefit of doubt).

My brain is putting all of this together… chronic underlying stress from being itchy (despite my friend doing an a-mazing job keeping her rugged and as protected as possible!), weird appetite for a pony and not fat despite lots of pasture, girthy and not happy in her work.

It was suggesting ulcers to me, and it was suggesting glandular ulcers (the ones down the bottom of the stomach), as I couldn’t see how there were any risk factors for the squamous ulcers up the top of the stomach.

So, into a scoping day we go, and look what we found, mild pyloric ulcers.

In a way it didn’t surprise me. BUT when we think about the typical risk factors for ulcers, this pony had none, aside from the fact she was itchy/stressed all the time!

The interesting dilemma for me is she has been with us for 2 months already. She has been (of course) on a well balanced diet since she arrived, gets a gut supplement (because I was suspicious of ulcers) and always gets lucerne before she is ridden (my daughter makes sure of this, I love seeing her get the lucerne as the first thing she does when saddling up!). The top (squamous) section of her stomach was pristine on scoping.

So what we don’t know is, are these ulcers healing and on their way out? Or are they persistent and will remain despite the non-itching and new diet.

I have chosen, in discussion with my vet not to treat these ulcers with any form of medication for now, keep up the diet and the supplement and rescope in 4 to 6 weeks and see what we can see!

I wanted to share though as it is such a good example of how (I suspect) stress can lead to ulceration as truly this pony had no other risk factors (aside from not being mineral supplemented on her pasture, which could lead to zinc deficiency and an inability to heal any lesions in the gut).

I hope you find this as fascinating as I did!



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Galaxy Still Has (BAD!) Ulcers

Ohhh Galaxy… almost 6 months now on a balanced diet and near pristine environment for reducing the risk of ulcers and she STILL has SEVERE ulcers!

This little girl had been on 2 months of oral omeprazole treatment before she came to me. She was scoped at the one month mark and had severe squamous and glandular ulceration.

On arriving here I had intended to put her on injectable omeprazole but with COVID and the drug not arriving and her behaviour and appetite improving we made the call to wait to medicate further until we could look in her stomach again. With COVID lockdowns this took a lot longer than anticipated!

We finally scoped her again last Friday (literally drove through floods to get her there, after being delayed so many times there was no way I was missing this opportunity!)… was so hopeful she would be better… was so gutted (pardon the pun!) that her condition is still so bad!

BUT this again serves to teach us a lot! This little mare looks great, shiny, in excellent (too excellent) condition, she is eating well, grazing normally, behaves like a normal horse, is happy now to be brushed all over and SEEMS like there is nothing wrong.

The gastroscope though tells a very different story… showing us it really is impossible to know what is going on in that stomach when just looking from the outside!

And it also teaches us that in at least some cases, pristine nutrition and management are not enough to resolve ulcers that are already in existence!


Where to from here?!

Thankfully we haven’t (yet) thrown everything at her. The wonderful Dr Doug Eddlington and Dr Benjamin Sykes have put their heads together and have come up with a plan for injectable omeprazole (given she didn’t respond to two prior months of treatment with the oral version) plus sucralfate. We will scope after 4 weeks on this regime and reassess.

What worries me more is WHY does a horse with close to zero risks for ulcers in her life stay so badly ulcerated?!

And even if we do treat and resolve these ulcers, are they just going to come straight back?? I’m not even sure I want to know the answer to this question just yet!

I guess we will see!

She won’t start treatment until January as we can’t scope her until around early February. If we miss the 4 weeks on treatment mark and scope her again to find ulcers we won’t know if they resolved with treatment but then came back or if they didn’t resolve in the first place.

And for me, that is critical information.

In the meantime I am not going to change anything about her diet or lifestyle.

I was so hopeful that being in a super-relaxed environment and on a specially formulated and balanced diet would help her naturally resolve those ulcers (it has with Spotty, yay!)… but alas, we need to move on the plan B!

Watch this space, will update you when there is more of the Galaxy journey to share!!



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Galaxy Update – 17th August 2021

With COVID locking down my entire state this month we are still without a follow up gastroscope so unfortunately I can’t give you a technical update on what is actually happening in Galaxy’s stomach.

What I can report on is her behaviour, which is probably the best indicator we have at the moment for what is happing inside.

I have been taking the opportunity just to spend little bits of time with Galaxy in the last week. I decided I would see how she reacted if I bought her out of her paddock to be brushed while haltered. I wasn’t going to push her and just brushed her neck and shoulders.

With lucerne hay to munch while I brushed she accepted the brush and I think even enjoyed it. No indication of her wanting to pin her ears back.

I also took her for a walk to find some tasty grass in our big pasture and while she grazed I brushed her all over, including her girth and belly. Again, no indication of wanting to pin her ears back (or kick) as she had grown accustomed to doing when she was badly ulcerated.

What the vet had to say…

I had Dr Doug, my vet out to check her stifle joints as she has odd movement in her back legs on occasion. Doug diagnosed her with ‘upward fixating patella’ and has suggested I use exercise to try and rectify this!

Doug and Stacey (our amazing vet nurse!) both commented on how much her behaviour had changed since she spent the night with them prior to her original scoping (back in May). And I have to say, she is turning into a pretty chilled out little girl. She no longer runs to the rails and whinnies when we take any of the other horses out of the paddock and she grazes a lot!

So outwardly she is doing well. Her coat still looks pretty foul but she should shed it soon and get her summer coat so will see how that looks before I worry too much about that.

Her diet remains almost the same. I have reduced her lucerne hay from 4 kg/day to 2 kg/day as she is in very good condition so I am having to balance calorie intake with managing ulcers!

I have also added a small amount (80 g/day) of copra meal and sugarbeet pulp to add a little more fibre variety to the diet. While her primary issue is in her stomach, I am also very conscious that the stomach is only one part of the entire digestive tract. I do think anything we can do to promote hindgut health will also support stomach health indirectly.

Moving forward

Next steps will be more groundwork with her and depending on how she accepts this we can move on to ridden work.

Stay tuned for our next update on Galaxy’s progress healing from gastric ulcers!



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Galaxy Update!

I’d love to be able to give you a really detailed update on progress with Galaxy.

Unfortunately though, with the scoping that was planned last week now postponed until ‘sometime in the future’ due to COVID restrictions, I can only give you an update on what I can ‘see’ from the outside.

Galaxy in all seems to be doing well

She is eating like a normal horse now, head in her feed bin and contentedly finishes her feeds.

For a few weeks now I haven’t seen her walk away from the feed bin and come back once (where when she first arrived she would do this repeatedly and often not finish her feed for hours).

She has also integrated well into my little herd. She and Spotty were a bit at odds with one another but this seems to have settled and they are happy to graze alongside one another now.

Galaxy LOVES Poet and is often standing so close she is touching him… makes me wonder if this will be a part of her healing process, this close company of a small herd of horses.

She grazes well now too. When she first arrived she would often just stand and stare off into the distance. Now she grazes more often than my horses (which I have to say is quite the achievement!).

She is a quirky little thing. And she definitely has a more anxious temperament than the other 3.

If there is something slightly unusual happening she will be the one paying the most attention (this may be because she is still newish, time will tell). And when we take one or more of her mates out to be ridden she is at the fence calling for them.

This ‘anxiety’ for want of a better term possibly has something to do with her being prone to ulceration. Will be interesting to see if it settles more over time. For the most part though she is a happy pony, and you honestly wouldn’t know she has (or at least had) severe ulceration.

I did brush her for the first time last week!

She was eating her lucerne hay, relaxed, no halter (which Felicity Davies pointed out may have removed her usual triggers for a negative reaction to being brushed… i.e. that she wasn’t anxious about being girthed up and ridden). She accepted the brush quite happily all over her near/left side. This hopefully is a good sign!

Her same diet continues

Grain free balancer, buffering gut supplement with amino acid support, full fat soybean, vitamin C and lots of lucerne as well as free access to grazing (which currently is a mix of 90% dead old native grass and 10% lush green cool season grasses).

I have added 40 ml/day of sunflower oil and will build this up slowly over time. I wasn’t able to find corn oil, so I chose sunflower as it has an equally high omega 6 content… if that freaks anyone out and you are thinking wouldn’t you feed a less inflammatory oil high in omega 3, I agree it does sound and feel very counterintuitive to feed a high omega 6 oil. But it seems the omega 6 and the proinflammatory cytokines it gives rise to are important for the healing of ulcers… I plan to review the data around this in more detail as soon as I get the time!

Next moves…

My next move with her diet will be to incorporate very small amounts of additional fibres with copra meal and beet pulp going into her feed and Rhodes grass hay fed with lucerne hay in the afternoons. I want to support her hindgut microbiota as much as possible. We sometimes forget that the gastrointestinal tract is all joined together. So while her immediate issue is in the stomach, promoting the best possible hindgut health is also a priority.

So far I am happy with her outward progress, but I am dying to see what is actually in her stomach! This process is teaching me patience!!

Until next time, love from Galaxy!



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Galaxy’s ‘Backstory’ and the Story so Far

If you missed her introduction, meet Galaxy! Galaxy is a 7-year-old arabian riding pony who has been given to me as she had such severe gastric ulceration and associated behavioural issues her previous owners felt she was unsafe and also not fit for sale. From what I’ve seen of her so far, I agree.

BUT, they also loved this little horse and wanted someone to try to heal her. I just happened to see her gastroscope and said she would make a great case study… so here she is! She is such a sweet girl, but with all her pain she just couldn’t hold her behaviour in.

My hope is that Galaxy’s story will help educate thousands of horse owners around gastric ulceration, and especially the behaviours horses will display to try and tell us, as their humans, that something is wrong! It’s not them being naughty, its them being in severe pain!

With that hope in mind, let’s get the story started!

Galaxy’s Backstory

I have very little backstory on her other than the home she came from was loving but inexperienced. The little bit I saw of her being handled there they were quite anxious with her. She was kept in a paddock, with another horse who was a seemingly very sweet thoroughbred. He was the dominant one though they apparently got along quite well. He would occasionally bite her over food.

There was a kelpie dog there, though she doesn’t seem too bothered by dogs here with me. She doesn’t like them, but she doesn’t seem scared of them either.

She had been with this family for around 6 months. During that time she ate only the native pasture available, which seemed plentiful but of poor quality. She was in good body condition.

Prior to this, I’ve very little background. Depending on how difficult she is to treat, I may go digging back further to find out more. Who knows how long this has been an issue for her. I believe she hadn’t been with the previous owner for long and she was sold for a relatively low price. Whether that suggests her behaviour (i.e. her ulcers) were an issue with this owner too I don’t know?

She is registered so I can see on her papers that she was bred by a stud but owned by someone else at the time of registration. So in her short life she has had quite a few homes, I am the 5th home that I know of so far! A lot for a 7-year-old.

Why Does She Have Ulcers?

The honest answer to this is I have no idea. Why does a pony who is not in work, not travelling, in a 24/7 paddock environment with a paddock buddy with constant access to forage have grade 4 squamous and glandular ulcers. Her stomach looked like it had been attacked with a carrot grater! (So bummed the recording didn’t work, so I can’t show you!).

But here are some possible contributors:

Stress – moving homes, potentially not always having paddock buddies or being handled by anxious handlers.

Chronic Pain – poor saddle fit or issues in her back, or hooves or mouth or ovaries or… And I do wonder if the glandular ulcers developed first which then predisposed her to the squamous ulcers by reducing feed intake and increasing the acidity and risk of acid splash in the stomach. Theory only but it is about the only one I can come up with to explain such severe squamous ulcers in a horse with constant access to forage and not in work.

I should note here she appears sound, and we have done her teeth and there were no major issues in her mouth, in fact not a single laceration that may have been causing pain. I had all my fingers crossed that we would find a mess in her mouth as it may have given us some explanation for her ulcers, but alas, (and also relief) she has a good little mouth!

I will keep looking for any possible contributors to chronic pain for her!

Drought – while the drought has been broken in our region for a while now who knows what her circumstances were during the recent prolonged drought. Is it possible she struggled for feed during the drought, developed ulcers then and hasn’t had the support to help heal them since?


This (maybe obviously) is the big one for me! Her diet I know was suboptimal and I am 99.9% sure it would have been deficient in multiple minerals, including zinc, some amino acids, vitamins and potentially also fatty acids. It’s a bit of a cocktail of deficiencies that would likely have predisposed her being less able to repair any damage that was occurring in her gut, leaving her susceptible to the severe ulceration present in her gut.

There are likely many more factors that may have contributed to her ulceration.  We will likely never know what caused her ulcers. Big question is can we fix them!!

Treatment So Far

When I first saw Galaxy being scoped she had been on oral omeprazole for a month. She still had grade 4 ulcers, top and bottom. She was only kept off pasture for an hour prior to the omeprazole being administered which could well have rendered it ineffective. Or she may be one of the small % of horses that oral omeprazole is seemingly ineffective for, regardless.

After that scoping she was continued on omeprazole, put onto a grain-free complete feed, and had a gut supplement added to her diet. This continued for another month with no improvement in her behaviour. But she hasn’t been scoped again so we don’t actually know what has happened in her stomach. Her next scope is in 2 days.

Since coming to me I have really just focussed on her diet. I have incorporated a lot of lucerne, taken her off the complete feed as she was quite fat and have switched to a grain-free balancer pellet, focussed on amino acids, using soybean and supplemental amino acids, added vitamin C (it’s a theory, will explain more later) and she gets a gut supplement twice a day to help with buffering her stomach and supporting her hindgut.

As we go through this story I will explain why I am using these ingredients. It is too much detail to add just now.

So far so good. When she first arrived her appetite wasn’t great. She picked at her lucerne hay and often left a lot of it uneaten. She picked at her feed and for a couple of days hardly ate anything. Which gave me a small taste of the frustrations of a horse with a poor appetite! And she was terrible at grazing, preferring to stare off into space than actually put her head down and eat.

But about a week and a half in and she is was eating like a proper horse, finishing her hay and spending longer amounts of time grazing.

Where To From Here

First things first, she gets scoped again in 2 days and then I will know what I am actually dealing with! Once we know, my vet and I will put together a plan for medication and ongoing nutrition.

I will also keep looking for any other stressors or pain that may be predisposing her to the ulceration we are seeing.

And I’m also really focussed on keeping her calm, integrating her into my herd so they can teach her to be a chilled out pony that loves to graze and eat normally, and on slowly slowly helping her to accept being scratched all over without pinning her ears back! I’m doing very little with her in terms of handling because I don’t think it is fair to expect her to be able to behave well when she is likely still in a lot of pain.

Watch this space! Will update you once this scope is done!



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Horse looking out from his stable

Ulcer Medication + Bute: Is it safe?!

Is using omeprazole for the prevention of gastric ulcers while treating horses with phenylbutazone (bute) best practice?

Recent research indicates perhaps not.

Prescribing omeprazole alongside treatment with phenylbutazone has become common to reduce the negative impact the pain medication is thought to have on gut health and development of gastric and colonic ulcers.

A recent study, published in the Equine Veterinary Journal by the team at Louisiana State University set out to evaluate the effect of omeprazole on phenylbutazone-induced gastric ulcers, including squamous and glandular ulcers.

Their major findings were:

  • Horses treated with a combination of phenylbutazone in combination with omeprazole had more intestinal complications, many of them severe, some resulting in death or horses having to be euthanised.
  • Omeprazole treatment was effective in preventing the worsening of phenylbutazone induced glandular ulcers.
  • Sudden changes in management should be avoided during treatment with phenylbutazone and in combination with omeprazole.

The take home message?

The use of these two drugs together needs to be carefully considered as it is not universally safe to do so. If you can avoid using both at the same time and use other ways of supporting gut health while horses are on bute, then you probably should.

If you love the details like we do, keep reading!

The Study

Twenty-two horses from the universities teaching herd were enrolled in the study based on inclusion criteria of >3 years old, with squamous and glandular ulcer scores less than 2 and no signs of systemic disease.

Horses were acclimatised 2-3 days prior to initial gastroscope. Prior to this, the horses were fed a diet containing pasture, mixed grass hay and 1kg of pelleted feed (starch max. 17%).

During the study period, horses were individually stalled and fed a diet consisting of mixed grass hay and 1kg grain-based feed (starch max. 33%). Grain based feed was changed from 1kg Purina Omolene 100 to 0.5kg Omolene and 0.5kg Purina Strategy (starch max. 10%) daily after the first cohort due to observations of colic signs.

Horses were allocated into one of three groups (randomised block design based on initial glandular score) and treated for 7-14 days with one of three treatments:

Treatment 1. phenylbutazone paste 4.4mg/kg orally every 12 hours

Treatment 2. phenylbutazone paste 4.4mg/kg orally every 12 hours + omeprazole 4mg/kg orally every 24 hours

Treatment 3. placebo (control) of corn syrup 10ml orally every 12 hours.

There were four cohorts due to stall availability.

Horses were fed two biscuits of hay at 4pm in the evening alongside feed and no hay was present at time of medication administration in the morning. Omeprazole was administered first the following morning, followed by phenylbutazone 30 minutes later, followed by hay and feed.

On day 0, 7 and 14, following 16-18 hours fast, gastroscope was performed by an investigator blinded to treatment. Signs of colic and diarrhoea were observed and recorded throughout the study period.

Gastric fluid and blood was collected on day 0 and day 14 (unless withdrawn earlier). Horses were withdrawn from the study if adverse effects (colic, lethargy, diarrhoea) were identified that required medical intervention or if glandular or squamous ulcers grade 4 was observed.

Due to adverse effects seen in treatment groups in the first cohorts, the last study cohort underwent treatment for 7 days only.

The Results

The results from this study are quite complex due to the complications within treatment groups and as a result, horses being withdrawn from the study but here are the main findings.

Gastric Ulcers

No effect of treatment on squamous ulcers was seen. Glandular ulcers increased by one score in the phenylbutazone group compared with no significant change in the phenylbutazone + omeprazole group.

Interestingly, no obvious change in glandular ulcer scores was seen in the control group however a trend towards increasing squamous ulcer scores which may indicate the role diet and management may play in squamous ulcer formation.

This was also seen in the phenylbutazone group but not in the phenylbutazone + omeprazole group. One horse in the control group appeared not to cope with changes in management with increase of glandular and squamous ulcer scores from 1 to 4 in just 7 days.

Intestinal Complications

Intestinal complication was observed in both treatment groups. These included two out of a total of seven in the phenylbutazone group (including large colon impaction and small colon impaction).

And six out of eight in the phenylbutazone + omeprazole group (including large colon impaction, small colon impaction, colic of undetermined cause, diarrhoea, colitis and secondary sepsis resulting in death and ulcerative colitis with septic peritonitis leading to euthanasia).

No horses in the control group developed complications.

Study Limitations

The authors acknowledge that a high dose of phenylbutazone was used (4.4mg/kg twice daily) however justified that this dose is occasionally used in clinical practice. Lower doses of phenylbutazone (2.2mg/kg twice daily) are generally recommended.

Sudden changes (2-3 days adaption) in dietary and housing management were also confounding factors however not dissimilar to clinical practice where horses may be brought in off pasture and hospitalised or stalled due to an injury.

Previous studies have shown changes in diet alter intestinal microbiome in horses and both dietary and housing management changes have been associated with colic. Therefore, this may have predisposed horses in the treatment groups to intestinal complications.

BUT it was not the determining factor as no complications were observed in the control group.


Care must be taken when treating horses with omeprazole alongside phenylbutazone.

The exact cause of complications in treatment groups is unclear however the authors of this study suggest changes to microbial populations in the gut, altered gut motility and intestinal inflammation may have all contributed.

Talk to your veterinarian about any concerns prior to starting these medications, particularly if you are using both at once.

Importantly, try to minimise changes in management practices at the same time especially if you are introducing grain-based feed.

If your horse requires pain relief in the form of phenylbutazone, investigate alternatives to omeprazole that support gut health through other actions e.g. marine source calcium to buffer gastric acid, pectin or lecithin to protect the stomach lining and supplying the amino acids, glutamine and threonine, which help repair and protect the gut mucosa.

Plus be sure to reduce stress as stress is one of the biggest predisposing factors for glandular ulceration.

And if you really, REALLY like the details, here is the full article:

Ricord M, Andrews FM, Yñiguez FJM, et al. Impact of concurrent treatment with omeprazole on phenylbutazone-induced equine gastric ulcer syndrome (EGUS). Equine Vet J. 2021;53:356–363.



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Is long term use of gastric ulcer drugs increasing your horse’s risk of ulcers?

In humans, rebound acid hypersecretion (RAHS) is when gastric acid production actually INCREASES above normal levels when long-term treatment with proton pump inhibitors like omeprazole (the most common drug used to treat ulcers in horses) stops.

RAHS is known to occur in humans using drugs like omeprazole to suppress gastric acid secretion for extended periods of time (8 weeks+). The mechanism is understood to be:

  1. 1. Elevated gastric pH stimulates compensatory gastrin hormone release.
  2. Elevated gastrin causes changes to the enterochromaffin-like cells and increased levels of chromogranin A (CgA).
  3. These changes leads to increased capacity to stimulate gastric acid secretion.
  4. Gastric acid supressing drug is removed.
  5. Excess gastric acid is produced.

It is important to remember that a human’s and horse’s pattern of gastric acid secretion is different, so we can’t just assume that what happens in one will also happen in the other. But with the number of horses we see who are continually needing treatment for gastric ulcers, I do wonder if RAHS is occurring in horses.

If it is, what does this mean for your horse?

Well, if your horse has gastric ulcers and you can use omeprazole short term (4 weeks) to treat them, there may not be any implications as in humans it seems to be long-term treatment that causes RAHS.

BUT, if you are continually treating your horse for gastric ulcers, without success (i.e. you have one of those horses that no sooner are the ulcers healed then they are back again) or you have an OTTB that had been on long term ulcer treatment while in training (which is unfortunately common) you may need to take RAHS into consideration.

In humans, they have studied a slow withdrawal of the drug to try to stop RAHS occurring. But even with tapering the drug use off over 3 weeks, RAHS still occurred. Still it is worth discussing this tapering with your veterinarian for any horse that may be at risk.

What will most likely help is making sure the horse goes onto a diet and feed regime post treatment that will help naturally keep your horse’s stomach pH high AND stop the acid from being able to splash and reach the upper regions of the stomach.

A diet high in forage (hay or pasture) with at least some component of alfalfa (Lucerne) will be your best option. Having hay or pasture constantly available and keeping periods of time without feed short (less than 2 hours) will also help.

The more you can make your horse chew, the more he will salivate. And the more he salivates, the more buffered his stomach fluid will be. The more buffered it is, the higher its pH and the less likely it will be to cause ulcers. Supplements designed to elevate gastric pH may also be useful in the short term, post treatment.

And the big one, never ever ride your horse on an empty stomach! Fill him up with hay before you ride!!

For more on feeding to prevent ulcers, read our posts Avoiding Gastric Ulcers and Starch And Ulcers: What’s The Deal?



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Starch & Ulcers: What’s The Deal?

You may have heard it recommended that horses with ulcers should be fed a ‘grain-free’, low starch diet. It is believed that any starch may make ulcers worse. Or stop them from healing when the horse is being medicated to resolve ulcers. But is there any scientific basis for what has now become a popular recommendation? Let’s take a look!

Starch is fermented to volatile fatty acids (VFAs)

Like the rest of the horse’s gut, the stomach is full of bacteria. When grains AND forage enter the stomach, they are partially fermented. During fermentation, the bacteria produce volatile fatty acids. These VFAs are the same as what is produced in the hindgut during fermentation there. So they are not harmful to the horse. In fact they are beneficial.

Thing is though, in the stomach, they get mixed with the hydrochloric acid from the stomach and become ‘nonionized’. In this state, they can enter the epithelial cells of the upper part of the stomach, causing them to become inflamed, and swell, and ultimately make the stomach wall lining more prone to ulceration. This is what they understand to happen in pigs.

So everything you feed a horse will be partially fermented in the stomach. We do know however, that when we feed a grain based, high starch ingredients, higher levels of VFAs are produced. But does it increase the risk of gastric ulcers? Not necessarily.

Lucerne + grain = less ulcers than grass hay

In a study where horses were fed either lucerne + grain OR grass hay only, there was significantly higher levels of VFA in the stomach contents of horses fed lucerne + grain. BUT, the horses on this diet had less severe and fewer gastric ulcers than the horses fed the grass hay only diet. Despite the higher level of VFAs, horses on the lucerne + grain diet had a higher pH (less acidic) for 5 hours after feeding when compared to the grass hay only diet 1.

The researchers in this study suggest the high protein, high calcium characteristics of both the lucerne hay and the ‘grain’ (unfortunately, they do not specify what the grain was except to say it contained over 7 g/kg of calcium and was almost 15% protein, so it must have been a fortified commercial feed) created a buffering effect in the stomach and were able to keep the pH higher.

So here, the starch did increase VFA levels, but the diet containing the grain was also effective at keeping gastric pH higher. Combined, there was a protective effect against ulcers.

In a second study2, researchers found that of horses fed lucerne plus a commercial pelleted feed, 8% developed ulcers. Compared to 75% who developed ulcers when they were fed the same pellet, but with grass hay. In this same study, horses that started with existing ulcers all improved their ulcers scores by more than 2 when fed lucerne + pellet. But on the grass hay, only 2 out of 12 horses showed healing to the same degree. So it does appear lucerne is protective. And that feeding grain/starch doesn’t automatically mean a horse will be prone to ulcers.

What about high fibre versus low fibre?

We tend to think that a high fibre diet is always going to be better than a low fibre diet for minimising gastric ulcers. And there are varied reports in the literature. Research from the UK3 reported that a low fibre, high concentrate (32% starch pellet) diet had a lower number and severity of lesions versus a high fibre, low concentrate diet. Odd right!

The fibre fed during this study was ryegrass haylage. A trend is starting to appear with grass forage and a higher risk of ulcers! What we don’t know is why? Researchers in Denmark reported that horses with straw as their only source of forage had a higher risk of ulcers4 which may give some clues. Perhaps there are nutrients required for maintaining gut wall integrity that grass hays and straw are unable to provide.

The important point here is to realise that just feeding lots of forage is not enough to protect a horse from ulcers. And to recognise that adding grain to diets is not a risk factor in itself. It comes down to which forages are fed and how much grain/starch is fed AND how feeding is managed.

How much starch is OK?

The studies reported above show that grain can be fed without causing ulceration. So starch is not a simple ‘Cause & Effect’ with gastric ulcers. Or in other words, when it is fed in a certain way, it can be fed without causing ulcers. And can even be fed in a way to allow ulcers to heal. But is there a limit to how much starch you can feed?

The answer is YES! In a large study, 201 Danish horses from 23 different non-racing stables were scoped for ulcers. 53% of horses were reported as having an ulcer score of more than 2, with most of these occurring in the upper part of their stomach4.

Two risk factors related to the amount of starch fed were reported in this study;

  1. Feeding more than 2 grams of starch per kg of bodyweight per day (equivalent to 2 – 3 kg of a complete feed/day for a 500 kg horse, depending on the feeds starch content) doubled the risk of ulcers; and
  2. Feeding more than 1 gram of starch per kg of bodyweight per meal (roughly equivalent to 1 – 1.5 kg of a commercial complete feed per meal for a 500 kg horse, depending on the starch content of the feed) increased risk by more than three times.

So some starch it seems is perfectly OK. But there is a limit to how much should be fed ‘per day’ and ‘per meal’.

Feeding grain based feeds carefully is a huge consideration in managing the risk of ulcers. If your horse needs more energy than can be provided by the amounts of grain based feeds specified above, you should look at feeding oils or high energy fibres to meet the rest of your horse’s calorie requirements.

Does starch cause ulcers?

Too much starch increases the risk of ulcers. But when fed in a well put together diet, research has shown that diets containing grains resulted in less ulcers than grass hay only diets. So starch, itself, doesn’t appear to cause ulcers.

My horse is prone to ulcers. What should I do?

Good question! Here are my top tips on feeding a horse prone to ulcers:

  1. Feed lucerne hay – lucerne has been shown to buffer the stomach well and is protective against ulcers. It even seems to help them heal.
  2. Feed lucerne as chaff or haylage with your grain based feeds – this seems to help negate the possible negative effect of starch when it is fermented in the stomach.
  3. Feed lucerne hay before you ride – working horses on a full stomach is CRITICAL for preventing ulcers. The fibre stops the acid splashing around and the saliva created while chewing the hay helps to buffer the acid in the stomach. Using lucerne has the extra positive benefit with the buffering effect from the lucerne itself.
  4. Feed lots of forage – the more forage in the diet the better. It makes a horse chew longer, create more saliva and keeps the stomach full of fibre to help stop acid from the lower part of the stomach splashing up onto the top part and creating ulcers.
  5. Don’t allow more than 5 hours between meals – the longer the intervals between meals, the higher the risk of ulcers5. So make sure your horse is eating at least every 5 hours. For horses particularly prone to ulcers, keeping time without food as short as possible (no more than 2 hours) is advisable.
  6. If you feed grain based feeds, keep the amounts small – don’t exceed 1 gram of starch per kg of bodyweight per meal. The amount of pellet/sweetfeed/cube/grain you can feed per meal depends on the starch content of the feed. The table below shows you maximum amounts that can be fed per meal of a feed, based on its starch content, for a 500 kg horse. If you are unsure of your feeds starch content, don’t exceed 1.5 kg of feed/meal (for a 500 kg horse).


Starch Content (%) Maximum Amount/Meal for a 500kg Horse (kg)
20 2.5
30 1.7
40 1.25
50 1


  1. Make sure horses ALWAYS have access to water – water deprivation has long been known to increase risk of ulcers. So allowing constant access to water is important to reduce the risk of ulcers.

Should I go grain-free?

While the studies above show us that feeding grains, in diets that also contain lucerne can result in ulcers resolving, if you are more comfortable going grain-free then it is certainly an option. Using high quality, grain-free products that are high in protein and fortified with calcium are likely going to work well for a horse prone to ulcers. As far as I can see there are no studies to confirm this… something for future research to work on!

It is just important to remember that this is not essential. Grain based feeds can be used, as long as they are used carefully.


  1. Nadeau JA, Andrews FM, Mathew AG, et al. Evaluation of diet as a cause of gastric ulcers in horses. Am J Vet Res 2000;61:784-790.
  2. Lybbert T, Gibbs, P., Cohen, N., Scott, B., Sigler, D. Feeding Alfalfa Hay to Exercising Horses Reduces the Severity of Gastric Squamous Mucosal Ulceration. AAEP Proceedings 2007;53.
  3. Boswinkel M, Ellis A, Sloet van Oldruitenborgh-Oosterbaan Mm. The influence of low versus high fibre haylage diets in combination with training or pasture rest on equine gastric ulceration syndrome (EGUS). Pferdeheilkunde 2007;23.
  4. Luthersson N, Nielsen KH, Harris P, et al. Risk factors associated with equine gastric ulceration syndrome (EGUS) in 201 horses in Denmark. Equine Vet J 2009;41:625-630.
  5. Luthersson N, Nielsen KH, Harris P, et al. Risk factors associated with equine gastric ulceration syndrome (EGUS) in 201 horses in Denmark. Equine Veterinary Journal 2009;41:625-630.


Meet The Author: Dr Nerida McGilchrist

Dr Nerida McGilchrist is FeedXL’s co-founder and equine nutrition specialist. She holds a degree in Rural Science, a doctorate degree in equine nutrition and nearly 20 years of full time, on the ground experience in feeding all types of horses. To learn more about Nerida and to ‘meet’ the rest of the FeedXL team, check out our About Us page here.



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