Q: Does gastric ulcer medication reduce nutrient digestion in horses?
Someone asked me this in a recent seminar and it reminded me that when I was studying during my PhD tenure we had looked at the effect of pre-incubating grains in equine stomach fluid on the digestion of starch from those grains.
And what we found was that starch from grains that were exposed to equine stomach fluid before being digested by small intestinal enzymes was between 17% (extruded rice) and 104% (cracked triticale) MORE digested than starch that wasn’t exposed to the stomach fluid. So the stomach fluid was having a definite positive influence on the digestion of starch.
What we can’t say from this research was how much of this increased starch digestion was due to the stomach acid and how much was due to the protein digesting enzymes the are present in stomach fluid that would be starting protein digestion and making access to the grain starch easier for the starch digesting enzymes in the small intestine.
The thing to remember though is that the protein digesting enzymes in a horse’s stomach fluid rely on the stomach acid to activate them. So regardless of whether the improved digestion was due to the acid itself or the protein digesting enzymes, if you stop acid production using ulcer medications you will lose both the acid and the enzymes.
So, if we use medications like ranitidine and omeprazole to reduce gastric acid secretion in horses we are very likely reducing the digestion of at least some nutrients further down the gastrointestinal tract.
What to do??? Well, if your horse has ulcers this is by far the most important consideration, you need to medicate to get rid of the ulcers as quickly and as effectively as you can.
BUT, once the ulcers are gone it is recommended you use good management practices to keep your horses chewing, their stomachs full and buffered with saliva and their minds calm instead of constantly using medication to prevent ulcers. That way you are allowing their gastrointestinal tract to function the way it was designed (albeit I would love the opportunity to redesign parts of their gut!) and allowing the digestion process to be as effective as possible.
More info on feeding to prevent ulcers in our article ‘Avoiding Gastric Ulcers’ here.
Happy to share the method for the in vitro assay used to conduct this work with anyone who would like the details!
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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We talk a lot about a horse’s gut bacteria and how they impact health… have you ever stopped to think about your gut bacteria and how they might be influencing your health?? This relatively new area of science is quite literally mind blowing. These tiny critters control us in so many ways and have such a massive impact on our life that it is truly worth thinking about how what you eat affects them (and then how they affect you).
Here are a few very quick bits of info that are quite amazing… you ready?!
1. Bacteria in your body outnumber your human cells by 10 to 1, so in actual fact, we are 10 parts bacteria, 1 part human.
2. Bacterial DNA in our body outnumbers our human DNA by 100 to 1, so in that respect we are only 1% human (Don’t think about that too much!!)
3. Bacteria like to tell us what to eat. Certain foods are their favorites so in order for them to survive, they will make us go and eat their favorite foods! This is OK if you have a nice healthy population of fibre/vegetable loving bacteria in your gut. But it becomes an issue when you have accidentally bred up a sugar or fat loving bunch of microbes. Next time you are craving sugar or fatty food you can probably blame your bacteria! In saying that, if you starve the ones you don’t want in there (e.g. stop eating sugar) the cravings should lessen!
4. Bacteria produce mood altering hormones like dopamine and serotonin. Studies suggest half of these hormones in our body come from our intestine! Get the wrong bacteria and you could very likely be in the ‘wrong’ mood!
5. Bacteria can reduce or increase anxiety. In mice, taking the gut bacteria from nervous mice and introducing them to calm mice made the calm mice anxious! Scary huh!!
This list could go on (and on… and on!). There are known relationships between diseases like asthma and Type 2 Diabetes and gut bacteria for example. Suffice to say they are important little critters and probably have far more of an influence on you (and your horse) than you realise.
Eat well! Keep those bacteria healthy… we can’t help you much there (other than eat more real food and less junk) but certainly when it comes to feeding your horses, always think about how what you are feeding is affecting their gut bacteria. If you have time, have a read of our article on feeding for hindgut health! https://feedxl.com/15-keeping-the-hindgut-healthy/
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Poet and I (Nerida) headed out a few weeks ago to do some real work mustering sheep (not that we did anything useful, we were just along for the ride!). There were 5 of us on horses, saddled up by 6:30 am and in incredibly steep, rocky, tough (but stunning!) terrain for 6 hours. At various points we dismounted and slid (feet sideways) down parts of the mountainside because it was too steep to ride. Sheep were tripping and rolling down the hill (amusing! but gives you an idea of how steep it was!!).
Anyway, here is me, very conscious of gastric ulcers, giving my horse lucerne/alfalfa as I saddled up, letting him pick what grass we could find while out riding if we were stopped for any time so he at least salivated a little bit and immediately giving him water and more lucerne/alfalfa on return to where we had saddled up… meanwhile stifling my panic at watching the other horses eating nothing and trying not to think too much about what was going on in their stomachs.
I asked one of the guys, an experienced horseman, if he worried about ulcers, and it soon became clear that there was no understanding of how a horse’s stomach worked and the negative impact of not feeding them for such long (long!) periods of time (his horse had a couple of hours trip home).
I also asked recently at a seminar who could confidently sketch a horse’s gut or explain how it works and no-one was able to. And I get this… I had no idea what a horse’s gut looked like or how it worked the entire time I rode in my pre-nutritionist life!
The thing is, a horses stomach never stops secreting gastric acid. So even when your horse is not eating it is filling the lower part of its stomach up with acidic gastric juices. While the stomach is full this isn’t an issue as the dense matt of fibre in the gut will stop the acid from splashing around and burning the unprotected lining of the upper section of the stomach.
Problems start though when horses are off feed for long periods like this and end up with a pool of acid and an empty stomach. Combine that with the movement of being ridden and you get acid splashing up and quite literally burning holes (causing ulcers) in the top part of the stomach.
So here is my plea! Please help us to educate people on how a horse’s stomach works and what they can do (really simple things) to keep their horse’s stomach and therefore their horse healthy and pain free. Share this article on Avoiding Gastric Ulcers with them and have them understand that a horse’s stomach should never be empty and that as much as is practical you should never work a horse on an empty stomach.
Thank you!! From us and from all of the horses who will be so much better off when their owners understand how they work just a tiny bit better.
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This is an interesting read on the impact of proton pump inhibitors (PPI) like Omeprazole (the major drug we use to treat equine gastric ulcer syndrome) on the gut bacteria in humans: https://gut.bmj.com/content/65/5/740
While these drugs are a huge help in setting up an environment in the equine stomach where ulcers can heal, they are overused in many horses (some racehorses are never taken off these drugs) to prevent ulcers in place of management systems that will reduce a horse’s risk of ulcers (like feeding a forage meal to fill the stomach prior to work).
What are PPIs doing to the equine gut bacterial populations? One study (https://beva.onlinelibrary.wiley.com/doi/pdf/10.1111/eve.07_12792) shows no impact on equine fecal bacterial populations, but use of omeprazole in these horses was only short term and the study doesn’t specify the dose used. The fecal microbiota also aren’t necessarily reflective of what is happening further up the gastrointestinal tract.
Something to keep in mind if you have a horse on a PPI medication long-term. More research is needed.
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Gut health! It’s so important but also really hard to ‘measure’. One way to get a bit of an indication of what your horse’s hindgut health is like is to check faecal pH.
A healthy hindgut will stay at quite a neutral pH, close to 7. At this pH the good fibre fermenting bacteria will be living happily ever after and doing an amazing job of digesting fibre for your horse.
A high pH (over 8) may indicate that there is not a lot of fibre fermentation happening in the hindgut for some reason, while a low pH (less than 6.5) may indicate that there is too much fermentation of starch and sugars happening. The good fibre fermenting bacteria don’t like living in these lower pH conditions and will be starting to shut down. If pH goes below 6.2 you can be almost certain that a lot of your good fibre fermenting bacteria will be starting to die and your horse will lose the ability to digest fibre (which then causes all sorts of problems including weight loss and vitamin deficiency).
So if you want to do a quick check on hindgut health, grab a ‘soil pH test kit’ (google that, you will find plenty of options for inexpensive kits) and use it on a fresh pile of your horse’s manure. You might find that pH is just right, or you may just find that something is a little out of kilter and you need to adjust the diet to get it back to a more neutral pH.
Have fun!
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When a horse eats, much of its feed is made up of LARGE carbohydrate, fat and protein molecules. The horse can only absorb tiny little molecules from its gut (because if big stuff was able to cross from the gut into your horse’s body all sorts of bacteria, toxins and general muck would pass into the body and cause disease havoc!).
So before absorption from the small intestine can occur, the big stuff must be chopped up into little stuff. And it is enzymes in your horse’s gut that do this chopping.
It is easiest to think of digestive enzymes as little pairs of scissors. Let’s look at starch as an example. Starch (found in cereal grains like barley and corn/maize) is made up of lots of glucose molecules, all joined together. The job of the starch digesting enzymes in your horse’s small intestine is to cut starch into single pieces of glucose. Then it is the glucose that your horse is able to absorb.
Each nutrient has its own specific set of enzymes in your horse’s small intestine. So there are specific enzymes to digest/chop up starch, protein and fats/oils.
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Soybean naturally contains an anti-nutritional factor called trypsin inhibitor. Trypsin inhibitor is a compound that actually blocks the action of trypsin (which is an enzyme, or as I call them, a little pair of scissors, in the horses gut that cuts up protein so it can be absorbed by the horse). When trypsin is blocked by soybean a horse can no longer digest protein… not very useful right?!
So if soybean contains stuff that stops a horse from digesting protein, why on earth would we use it in a horse’s ration???
This is talked about a lot and often given as a reason why soybean should not be fed to horses. BUT, if you’ve been hanging around us here at FeedXL for a while you will have heard us say many times that if soybean is cooked properly trypsin inhibitor is destroyed which then makes soybean perfectly safe to feed. And given it is the best of the best when it comes to quality plant protein it makes a valuable addition to diets in so many ways.
To check soybean products to see if they have been cooked properly there is a test kit called FeedCheck Soy (https://cbsbioplatforms.com/Store)… this kit gives a rapid visual check on whether soybean has been cooked enough to destroy the trypsin inhibitor. Soybean products that still have active trypsin inhibitor will show red coloring while properly cooked products will have no red coloring at all.
The photo above shows a test we did on two samples. We had completely raw full fat soybean on the left which is clearly bright red indicating it has all of its trypsin inhibitor still present. The product on the right is a commercially available (branded) product, which has been extruded and shows no hint of red coloring to demonstrate beautifully how, when done properly, trypsin inhibitor can be destroyed without destroying the actual soybean and all of its amazing protein! Happy days for those of us who love the benefits soybean can bring to a diet!
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Vitamin B1 has been observed to have an influence on behaviour in multiple animal species, including horses. A horse will meet its vitamin B1 requirements via the vitamin B1 it eats in its diet and from vitamin B1 produced by the bacteria in its hindgut.
There are two main families of bacteria living in your horse’s hindgut:
1. The fiber fermenting bacteria who love to ferment fibre from the forage your horse eats. These little critters are the ones we consider the ‘good bacteria’; and
2. The starch and sugar fermenting bacteria who prefer to ferment starch and sugars. These we generally consider to be the ‘bad bacteria’.
The good bacteria PRODUCE vitamin B1 that your horse can then absorb and use.
On the other hand, the bad bacteria produce a compound called ‘Thiaminase’ that actually destroys vitamin B1 (also known as thiamine) that is in the gut, making it useless to your horse.
If your horse has too many bad bacteria, and not enough of the good ones your horse may not get enough vitamin B1 and behavioural changes may occur.
How do you avoid this? Keep your horse’s hindgut healthy with an abundant population of good bacteria. The main two things you should do to achieve this are:
1. Feed lots of forage!; and
2. Never feed uncooked grains (with the exception of oats for some horses)
Do you have a question or comment? Do you need help with feeding?
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We have all been told ‘little and often’ when it comes to feeding horses. But why?
Well, when you consider horses are ‘grazers’ and their gut has been designed to work best with small amounts being consumed constantly over long periods of the day and night (they eat for up to 17 hours a day, can you imagine having to do that!) it makes sense that they should be fed small meals frequently.
But here is a visual (in words) on why it is best to feed little and often… In the horse’s small intestine there are things called enzymes, which are like tiny pairs of scissors. An enzyme’s job is to cut big things like protein, starch and fats up into very small things like amino acids (the building blocks of protein), glucose (the building block of starch) and fatty acids (a building block of fats).
If these proteins, starches and fats don’t get chopped up they will not get absorbed because they are far too big to cross the intestinal wall intact. So for absorption to occur, these enzymes MUST chop the big stuff into little stuff!
Picture this…
Imagine you have a pair of scissors and are tasked with the job of cutting up a long piece of ribbon. The ribbon is trailing from a person going past you very slowly. If you have plenty of time to chop the ribbon multiple times then you can get it into small pieces. This is what happens in the gut. If a piece of protein for example goes moving through the small intestine very very slowly, the little enzymes have plenty of time to chop it up into amino acids so it can be absorbed.
Now imagine if the person holding the ribbon runs past you and you have to chop it up… you might get one shot at it before it is gone. And this is exactly what happens in the gut. If feed is moving too quickly through the gut the poor little enzymes simply don’t get enough time to chop anything up. Meaning the feed simply won’t be absorbed.
So back to meal size and the little and often concept… when you feed small meals, the feed will move nice and slowly through the gut and the enzymes will be able to do their job and fully digest it so your horse gains full benefit.
Feed large meals and all of a sudden you increase the speed with which it will travel through the gut and reduce the amount of time the enzymes have to do their cutting… meaning your horse misses out on a lot of the value from that feed. It will be digested to some extent in the hind gut but a lot of value is lost (and your $ wasted).
So while not the only reason you should feed little and often, it is a really important one to keep in mind.
If you have a horse struggling to gain weight eating huge feeds, you might find you get better results by feeding less! Something to consider
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Ask any zoo-based nutritionist and they will tell you that understanding a particular animal’s gastrointestinal physiology is the key to understanding what and how to feed them. The shape, size and structure of an animal’s gut reflect what their natural diet consists of, and horses are no exception. Understanding the gastrointestinal tract is the key to feeding your horse correctly.
We know that horses are herbivores and we know that they graze for long periods each day if they have pasture available. You will also be familiar with the advice to feed ‘little and often’ and to base your horse’s diet on fibre. The reason why you should do these things lies in the way their gut is structured.
Monogastric Hindgut Fermenter
The horse can be classified as a monogastric (or single stomached) hindgut fermenter whose gastrointestinal tract consists of the mouth, stomach, small intestine, caecum, large colon, small colon and rectum (Figure 1).
Figure 1: The structure of the gastrointestinal tract of the horse (Drawing L. Ferguson)
The Mouth
Horses use their mobile upper lip and incisors to select and shear forage from its base or to select and pick up hay or concentrate feeds they are fed. Horses are incredibly clever with their lips and teeth and are able to carefully select feeds and forages that they either wish or do not wish to eat (often much to the frustration of their owners).
Once the feed is in the mouth it is pushed by the tongue to the molars at the back of the mouth where it is chewed extensively. During chewing, the particle size of the feed is reduced to facilitate digestion further down the gastrointestinal tract and, importantly, it is mixed with saliva. The saliva lubricates the feed, making it easy to swallow (thus preventing choke), and also provides some buffering to protect the upper regions of the stomach from the acids produced in the lower regions of the stomach. Once the feed is chewed sufficiently it is swallowed and travels down the oesophagus into the stomach.
The Stomach
The stomach of the horse is a “J” shaped organ with a capacity of approximately 5 – 15 litres meaning the stomach comprises around only 10% of the total volume of the horse’s digestive tract. The stomach has two major functions. These are:
The storage and controlled release of feed into the small intestine; and
The initiation of protein digestion.
The stomach of the horse is unique in comparison to other monogastrics like dogs and humans (both meal feeders) for two reasons: the first is that acidic gastric juices are constantly secreted into the stomach (dogs and humans only secrete gastric juices when they see or start to eat food); and the second is that feed tends to pass rapidly through the stomach (unlike in carnivorous monogastrics like dogs where food spends a large amount of time in the stomach).
While both of these features are well suited to the grazing horse consuming a high fibre diet, it is likely that these same design features play a role in the incidence of gastric ulcers in horses. For more information on gastric ulcers in horses, read our FeedXL Newsletter #8 – Equine Gastric Ulcers.
Once feed is released from the stomach it enters the small intestine.
The Small Intestine
The small intestine is where a majority of protein, fats and non-structural carbohydrates (starch and simple sugars) are digested and absorbed. The small intestine of a 500 kg (1100 lb) horse is approximately 20 to 27 meters long and has a capacity of 55 to 70 litres.
When feeds enter the small intestine they are mixed with digestive enzymes. These enzymes include proteases that digest protein, lipases that digest fats and glycanases, that digest non-structural carbohydrates. These enzymes act much like scissors, cutting the large protein, fat and carbohydrate molecules into very small pieces that can be absorbed from the small intestine into the horse’s bloodstream or lymph for transportation around the body.
The passage rate of feed through the small intestine is relatively rapid, with feed passing through the entire small intestine in as little as 45 minutes. Given that the feed can move so quickly it is very important that everything entering the small intestine is easy to digest. Horses have a natural ability to extensively digest fats and proteins, however starch from raw cereal grains is very difficult for horses to digest in the small intestine. For this reason, cereal grains must be cooked to improve its digestibility in the small intestine (read FeedXL Newsletter #18 Feed Cooked Grains).
At the end of the small intestine nearly all of the fat, simple carbohydrate and a majority of the protein components should have been digested, leaving only the structural carbohydrate or fibre components to continue on and enter the hindgut.
The Hindgut
In the horse, the caecum, large colon, small colon and rectum are collectively referred to as the ‘hindgut’. The hindgut is a specialised structure the horse has developed to enable them to digest high fibre forages.
Monogastric animals do not possess the enzymes necessary to digest fibre. In order to extract the energy from fibrous feeds the horse houses billions of bacteria in its hindgut. These bacteria do possess the enzymes necessary for fibre digestion and they digest the fibre that enters the horse’s hindgut in a process known as fermentation. As bacteria ferment the fibre in the horse’s hindgut they produce volatile fatty acids (VFAs). These VFAs are absorbed and used by the horse as a source of energy. In fact, for horses consuming pasture or hay as the major component of their diet, these VFAs are their main source of energy.
The fermentation of fibre is a lengthy process. So the passage rate of feed through the horse’s hindgut is slowed dramatically, with feed taking from 50 hours to several days to travel from the end of the small intestine to the rectum where it is excreted as faeces, ensuring there is plenty of time for extensive fermentation to take place. This passage rate will vary however depending on how much feed a horse is eating, speeding up if large amounts of hay or pasture are consumed.
Any starch that is left undigested as it passes through the small intestine is also fermented in the hindgut. However, unlike the steady fermentation of fibre, the fermentation of starch is a rapid process. During this rapid fermentation, VFAs are produced in such large amounts that the ability of the horse to absorb them is overwhelmed. Lactic acid is also produced in large quantities and the accumulation of these acids in the horse’s hindgut causes a condition known as hindgut acidosis. Hindgut acidosis can cause serious diseases including laminitis and colic as well as loss of appetite, reduced production of vitamins, changes in behaviour and a reduced ability to digest fibre. Preventing starch from entering the hindgut must be a priority when feeding all horses. To read more about starch digestion in detail and about feeding grain, read our FeedXL Newsletter #18 – Feeding Cooked Grains.
The hindgut’s second most important function is to reabsorb and conserve electrolytes and water that have been secreted from the body into the gastrointestinal tract during the digestion process in order to prevent dehydration and electrolyte deficiency.
Understand the gut and you will understand how to feed
Because of the structure of the horse’s gut we know:
Horses should be fed little and often (to make sure their stomach which is continuously secreting acid is never empty),
Non-structural carbohydrates must be easy to digest in the small intestine and
The diet should always be based on large amounts of forage to keep their hindgut full and healthy.
When putting together your horse’s diet and daily feeding routine you should always be asking yourself, what impact if any will this have on the stomach, the small intestine or the hindgut. If you find something that is not ideal, look for ways you can make it suit the horse a little better. For example, if your horse is not able to graze and you are only able to feed your horse twice a day, put its hay into a feeder like a small hole hay net so it takes much more time to eat the hay than if it was just put into an open feeder or on the ground.
Feeding to suit the structure of the gut and keeping it healthy means you will always have a horse that is healthy, on the inside and out.
Do you have a question or comment? Do you need help with feeding?
We would love to welcome you to our FeedXL Horse Nutrition Facebook Group. Ask questions and have them answered by PhD and Masters qualified equine nutritionists and spend time with like-minded horse owners. It’s free!