Gut health! It’s so important for horses 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.
Interpreting 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).
An easy DIY hindgut health check
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!). This is where digestive enzymes come into the picture.
Why are digestive enzymes important for your horse?
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 digestive 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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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.
How hindgut bacteria affects your horse’s behaviour
If your horse has too many bad bacteria in its hindgut, and not enough of the good ones, your horse may not get enough vitamin B1 and behavioural changes may occur.
What you can do
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!
2. Never feed uncooked grains (with the exception of oats for some horses)
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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 horses 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, something to consider is that you might find you get better results by feeding less.
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We all know of a few ‘amazing’ stories about thoroughbreds rescued from the brink of going to slaughter and going on to be amazingly talented horses performing to Olympic level. And there are thousands of stories where thoroughbreds have been re-homed and re-educated to be dependable, talented riding horses.
The fact it can be done though doesn’t mean it is an easy task. Many thoroughbreds, and especially those who have raced take a lot of time and patience to re-educate and re-condition to live and work as a pleasure or performance horse. While there is no doubt that good education from a ‘steady hand’ is of utmost importance in a thoroughbred’s ‘transformation’, a large part of their transition from racehorse to riding horse is dependent on good nutrition. In this post we will look at the rather unique situation of feeding an off-the-track thoroughbred and the strategies you might use to get the best results.
The racing life
In a survey conducted in 2001 published in the Australian Veterinary Journal (Richards et al 2006) we found that thoroughbreds in racing stables are fed an average of 7.3 kg of grain-based feed per day. Some trainers fed as much as 13 kg of grain per day and feeding just twice a day was the norm.
Oats was the most commonly fed grain while corn, barley and commercial feed mixes were also popular choices. It was uncommon for trainers to use ‘cooked’ grains. As a result of these high grain diets fed in large meals where much of the starch would be considered indigestible in the small intestine we found that around 25% of horses were experiencing hindgut acidosis.
To make things worse for these horses very little forage is fed. Less than 1 kg/day of chaff was fed by a majority of trainers while horses only received hay an average of 1.5 times a day. We didn’t actually weigh the hay but the amount was small (probably around 2 kg/horse/day).
Essentially what you are likely to end up with when you take a thoroughbred directly from the racetrack is a horse whose gut has adapted as best it can to high grain diets and in the process has lost some ability to do well on high forage diets.
Problems that need to be ‘fixed’
Some of the problems associated with feeding and nutrition you are likely to encounter in these off-the-track thoroughbreds include:
An imbalance of the bacterial species in the hindgut. The horse’s hindgut contains two main ‘families’ of bacteria, those that ferment fibre and those that ferment starch and sugars (there is a 3rd group called lactate utilising bacteria but for the purposes of this topic we shall just focus on the two main families).What you would find if you could ‘see’ these two families of bacteria in the hindgut of a healthy horse fed a largely forage based diet is large populations of the fibre fermenting bacteria and much smaller populations of the starch/sugar fermenting ones. This however would be the opposite in a recently raced thoroughbred. You would see the starch/sugar fermenting bacteria in abundance while the fibre fermenting ones would be only in very small numbers. To make things worse, even though some fibre fermenting bacteria would still be present, the acidic environment the starch/sugar fermenting bacteria create means the fibre fermenting bacteria can’t function very well.What this all means is that fibre fermentation and therefore the horse’s ability to extract digestible energy from pasture, hay, chaff, haylage or high energy fibres like sugarbeet pulp, soybean hulls, lupin hulls or copra meal is severely limited. They might be eating a lot of fibre but will be able to digest very little of it.
Gastric Ulcers. It is estimated that as many as 90% of horses in race training have gastric ulcers. Gastric ulcers cause many problems but perhaps the two most relevant in the situation of feeding an off-the-track thoroughbred are the loss of appetite and weight loss. To get these ex-racehorses looking and feeling ‘normal’ they need to eat and they certainly don’t need anything like gastric ulcers to be causing further weight loss.
Hoof problems – Shelly, weak hooves that grow slowly are common issues seen in off-the-track thoroughbreds. Horses rely on biotin produced in the hindgut as well as dietary biotin to grow strong, healthy hooves. I believe, that largely due to the imbalance of bacteria in the hindgut, racing horses become biotin deficient and this is why we see so many with horrible hooves.
Poor appetites – It is quite common for ex-racehorses to have poor appetites. In many cases this is probably due to gastric ulcers but it may also be due to a vitamin B1 deficiency. As for biotin, horses rely on vitamin B1 being produced by the fibre fermenting bacteria in the hindgut to meet their requirements. When horses have a large amount of starch being fermented in their hindgut very little vitamin B1 is produced. And what is worse is the starch/sugar fermenting bacteria also produce ‘thiaminase’, an enzyme that actually destroys vitamin B1 in the gut. Both factors combine to create a vitamin B1 deficiency that is well known to cause a loss of appetite.
Getting fibre digestion ‘working’
The first critical step in getting a thoroughbred back to ‘normal’ is to restore the balance of bacteria in the hindgut and get fibre digestion working properly again. If you have the time, this is easily done by simply putting the horse on a forage only diet with as much forage available as the horse would like to eat. Over time, the starch/sugar fermenting bacterial populations will fall (because you simply aren’t feeding them their preferred food anymore) and the fibre fermenting bacterial populations will SLOWLY be restored.
The fibre fermenting bacteria are somewhat slow to reproduce so this isn’t something that is going to happen very quickly. You may also find that particular species of fibre fermenting bacteria have almost completely disappeared from the hindgut (something you really can’t test for) so it takes a long time for the population to get back to normal.
Many people ask if probiotics will help. The simple answer is no, the majority of them won’t. Many probiotics are designed to assist with killing or suppressing pathogenic bacteria in the gut and they predominantly contain lactobacillus species of bacteria. Lactobacillus are starch/sugar fermenting bacteria and one of the groups of bacteria you want to reduce numbers of, not increase.
What may help is using a fecal transplant, which is stomach tubing the horse with a strained slurry of manure taken from a healthy (worm free) horse on a high forage based with the goal of introducing the healthy bacteria from the donor horse to the gut of your off-the-track racehorse. This strategy is used with great results in feedlot cattle affected by acidosis to repopulate the rumen with ‘good’ bacteria.
While this process of rebalancing the hindgut takes time it is essential if you want to have a horse that has a gut that functions normally.
Fecal Transplant Method
Here is how to carry out a successful fecal transplant:
Place your off-the-track horse on omeprazole (full treatment dose) for a couple of days prior to fecal transplant (this will just cut the acid production in the stomach and make it more likely that the bacteria will make it through alive).
Take 500 grams of fresh feces from a suitable donor (one who is on a high forage diet with a healthy hindgut and parasite free).
Gently mix the feces in 2 litres of luke warm water, sieve to remove large particles and then add 100 grams of grass or other fibre only pellets (make sure they are grain free with a very low starch and sugar content). Other options would be alfalfa, soybean hull, beet fibre or lupin hull pellets.
At this stage be careful not to shake the mixture and run a sieve through the mixture to collect large particles as opposed to pouring the mixture through the sieve… this will help to keep the manures exposure to air as minimal as possible because oxygen will kill many of the good bacteria and these are the ones we want very much alive!
Administer while still warm via gastric intubation (this is a veterinary procedure and must be carried out by your veterinarian).
Reference: Mathijs et al (2019) Free Faecal Water: What do we know and can equine faecal microbiota transplantation be used to manage this issue? European Equine Health and Nutrition Congress, Utrecht, The Netherland
The hooves
To a large extent getting the hindgut functioning normally will correct issues the horse may have with its hooves being weak, shelly and/or growing slowly. Once the fibre fermenting bacteria are back and producing biotin again you should see good improvement in hoof quality (assuming requirements for nutrients like copper and zinc are being met). You may however like to use a hoof supplement to provide additional biotin to the horse in the short term. It is recommended that to positively impact hoof growth you should feed 20 mg of biotin per day for a 500 kg horse. If you do wish to feed biotin, use FeedXL to help select your hoof supplement. The amount of biotin in the diet is on the ‘Health’ tab. This will guide you in working out dose rates to meet your horse’s requirement for this nutrient.
Appetite
Again, getting the hindgut rebalanced will go a long way to improving the appetite of off-the-track thoroughbreds as they will be able to correct any vitamin B1 deficiency that may have been present. You can also use one of the many appetite or vitamin B1 supplements on the market to try and improve appetite. But remember that gastric ulcers are likely lurking in the stomach of your new horse and until they are resolved a poor appetite is likely to be present, regardless of what you feed or how you try to tempt the horse.
Gastric ulcers really must be treated so they resolve fully (talk to your vet about the most effective treatment options). There are some good US studies that show alfalafa/lucerne hay will help gastric ulcers to resolve given enough time. Incorporating alfalfa/lucerne into the forage base of the horse’s diet (up to 1 kg/100 kg BW or 1 lb/100 lb BW) may therefore also help to resolve ulcers and then to keep them at bay once treatment ceases. Once the ulcers are gone you should see a marked improvement in the horse’s appetite.
Gaining weight
Often the biggest priority for the owner of a new off-the-track thoroughbred is to get the horse gaining weight. While you could ‘feed the heck out of them’ and give them large amounts of grain based feed to put weight on them you are going to miss the opportunity in doing this of getting their entire gastrointestinal tract functioning ‘normally’ again. If you force weight gain with grain based feeds many of the problems discussed above will still be present and the horse still won’t be utilising fibre very efficiently. The end result is a horse that will need A LOT of feed to hold its weight long term (which is going to cost you a fortune).
So if time is on your side and you can be patient, hold off on pushing for weight gain until your horse has restored the balance of bacteria in its hindgut again and can properly utilise the fibre in its diet. Once it can do this you will find it takes a whole lot less feed to put weight on them. It is also crucial that any problems with ulcers have been resolved and that appetite has been restored before any attempt to put weight on the horse is made.
A note about fence walkers – Separation anxiety and fence walking is a common problem with newly off-the-track thoroughbreds. Given they are raised in groups and are virtually never left alone it is understandable. But if you think about it, a horse walking a fence instead of grazing has a high energy output and a low energy intake … there is no way you are going to put weight on a horse doing this. If you have a fence walker that needs to gain weight you are going to need to find it a buddy who is calm and spends a lot of time grazing and sleeping. The sooner your new horse can learn to do this the better.
Thoroughbreds are certainly capable of gaining and holding a lot of weight. It is just a matter of getting their gut (relatively simple) and their mind (sometimes not so simple … is that diplomatic enough?) sorted out. I see overweight thoroughbred weanlings, yearlings and broodmares all of the time, they are common. So, with some patience and strategy you will be able to get weight on and keep weight on your horse.
Problems with temperament
Thoroughbreds are typically thought of as being quite ‘hot’ – the “react and then think” types. This issue is compounded when you take a horse that only has very basic education, straight off the race track and immediately start trying to ride it at the same time as you are trying to feed it a high energy diet for weight gain.
Again, patience is king here. Give the horse time to adjust to its new environment and in the early stages of its re-education feed a very basic (but still balanced diet, be sure to use FeedXL to make sure all nutrient requirements are met), high forage, moderate energy diet with no grain. The more education you can give a horse before you really start feeding it ‘the good stuff’ for weight gain the better.
Feeding timeline
Here is a guideline for how you might approach feeding a thoroughbred that has come directly out of a racing stable:
Month 1 – Put the horse out to pasture or give it access to ad lib good quality grass hay and feed 1 kg/100 kg BW of alfalfa/lucerne per day. Use FeedXL to balance the diet correctly using a pasture balancer pellet or low dose vitamin and mineral supplement. If possible just let the horse be a horse without any pressure to be ridden or trained (other than to have good ground manners if these are lacking).
You should treat the horse for ulcers where applicable, have a faecal egg count done and worm appropriately and have teeth/hooves etc attended to by qualified professionals during this first month.
Months 2 to 4 – Depending on the how the horse is going and how well its hindgut is functioning by the second month you may be seeing an improvement in condition or a worsening of condition. If the horse’s condition is dropping away check for issues like ulcers (they could still be present), general anxiousness (is the horse pacing the fence constantly) or pain, for example a back injury that is making it uncomfortable for the horse to graze/eat properly.
During these months you may begin to add some high energy feeds but if the horse’s hindgut still doesn’t appear to be functioning correctly (eg its manure consistency is still not right or it is still really struggling to hold weight on a high quality pasture/hay diet) I would try to stay away from grains and grain based feeds. Use ingredients like grain free complete feeds (FeedXL will help you find truly grain free feeds), lupins, sugarbeet pulp, soybean or lupin hulls, full fat soybean and copra meal. If you are going to start riding the horse during this time these feeds might also help to keep your horse a little more level headed. Just mind you don’t give it a very high energy diet before you start riding it – for some horses that is just asking for trouble.
Months 5 to 12 – I would hope that by the 5th month the horse’s hindgut is back to normal or at least close to normal and by this time the horse will have semi-adjusted to its ‘new’ life. At this point in time you can consider other feeds including those based on grain. But PLEASE be sure to use cooked grain based feeds because the last thing you want to do at this point in time is put any sort of starch back into the hindgut.
The horse’s temperament and need for weight gain at this stage will determine how much feed you can feed. Still use forage as the major component of the diet and try to avoid feeding more than 800 grams of feed (approx. 1 lb) per 100 kg BW per day, being sure to split it into as many feeds as practical during the day.
You might also consider starting to add some high fat feeds like rice bran or straight vegetable oils to the diet for extra energy to help with body condition. At this point in time you need to be very careful to distinguish between condition/fat and muscle. Many thoroughbreds will look very thin when they are actually in good body condition, while they lack topline and general muscle. So be sure to read our post on Body Condition Scoring to help you determine if your horse needs more condition or needs to build muscle. The former can be done with feed alone. The latter needs a combination of high-quality feed and the right work (as well as a horse that is fully sound with no back or other pain that will stop it from using its muscles correctly).
Slow and steady wins the race!
The more time you allow an off-the-track thoroughbred to readjust to a forage-based diet the better the results you will get. A racing thoroughbred’s gut is adapted to eating a high grain diet. Ultimately you want your off-the-track thoroughbred to have a gut well adapted to doing well on a high forage diet. It takes time for the gut to readapt itself, build the right populations of bacteria and to heal problems like ulcers. But it is time well worth spending (unless you want to continue spending a fortune on grain based feeds and still having a horse that is really difficult to put weight on).
Taking it slowly in the first few months will mean you are going to get your horse where you want it to be sooner in the end. You will hopefully also be treated to a horse that is more relaxed and trainable than it otherwise would be if you try to put weight on too quickly using high energy feeds too early.
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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 blog: Avoiding 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 Grains for Horses: Cooked or Uncooked).
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 Grains for Horses: Cooked or Uncooked.
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.
It is absolutely critical to keep the hindgut healthy. For more information on the hindgut and how to keep it healthy, read our Keeping the Hindgut Healthy.
Understand the gut and you will understand how to feed
Because of the structure of the horse’s gut, we know that:
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.
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Like humans, horses are classified as monogastrics, however unlike humans, horses have a highly specialised and enlarged caecum and colon, collectively known as the ‘hindgut’.
What role does the hindgut play in maintaining overall health?
The hindgut plays some important roles in horse health including:
Fibre Digestion: horses don’t have the enzymes necessary to digest fibrous feeds like pasture and hay. However, in their hindgut they house many trillions of bacteria that exist in a symbiotic relationship with the horse. The horse provides them with somewhere warm and moist to live that has a constant supply of fibrous ‘food’ which the bacteria digest via a process of fermentation. In return, the bacteria give the horse a majority of the energy contained in the fibrous feeds in the form of volatile fatty acids (VFAs), which the horse absorbs and burns as fuel for muscle and organs.
Hydration: the hindgut and the fibrous material within it provide a reservoir of water for the horse which may be absorbed when needed to keep the horse hydrated.
Electrolyte Balance: the hindgut and the fibrous feeds within it also serve as a resource of electrolytes that can be absorbed when needed.
Vitamin Supply: the bacteria that ferment fibrous feeds also produce vitamins that may be absorbed and used by the horse, including B-group vitamins like thiamine (vitamin B1) and biotin as well as vitamin K.
Immune Function, Disease, and Behaviour: while we still understand very little about the full role of the bacteria who live in a horse’s hindgut, it is becoming increasingly clear in multiple animal species, including humans that the bacteria that live in the intestines play a huge role in control of immune function, the development of disease (like type 2 diabetes in humans) and also in production of hormones that can affect behaviour.
What are the implications of an unhealthy hindgut?
If the hindgut is compromised, many health problems can arise including:
Colic: Too little fibre, dehydration, the accumulation of dirt and sand or the fermentation of grain in the hindgut are just a few situations that may lead to serious cases of colic.
Weight loss: An unhealthy hindgut that does not have access to ample forage or has unbalanced bacterial populations due to the fermentation of grain can lead to a reduced feed use efficiency and weight loss.
Diarrhoea: A hindgut that is irritated by the accumulation of dirt and sand or parasites, rapid changing of diet ingredients, too little forage, oral antibiotics that disrupt hindgut bacterial populations or the excessive fermentation of grains can all lead to diarrhoea.
Vitamin deficiency: The fermentation of grains or use of oral antibiotics can disturb bacterial populations in the hindgut which in turn leads to a reduced production of vitamins like the B-group vitamins and vitamin K.
Loss of appetite: Allowing grains to be fermented in the hindgut can lead to the production of thiaminase, an enzyme that destroys the vitamin thiamine (B1). A thiamine deficiency can then lead to a loss of appetite.
Altered behaviour: Studies have shown that horses with acidic hindgut contents resulting from the fermentation of grain are more likely to exhibit abnormal behaviour. Altered behaviour may also arise if bacterial populations are disrupted which then changes production of hormones that affect behaviour.
Compromised immune function and development of disease: Again, this is a poorly understood area of research in equines but gathering evidence in multiple animal species suggests that if we disrupt hindgut bacterial populations, we are going to put our horses at increased risk of disease and compromised immune function.
9 tips to keep your horse’s hindgut healthy
Follow these tips for keeping your horse’s hindgut functioning normally:
1. Feed plenty of forage
A healthy hindgut is almost completely dependent on feeding enough forage. Bulky forage is needed to keep the hindgut full to prevent it from physically collapsing on itself or twisting up in a severe case of colic. Healthy bacterial populations are also dependent on having lots of fibre available for fermentation.
As a rule, feed a minimum of 1.5 kg per every 100 kg of bodyweight in forage per day (1.5% of bodyweight, which equates to a minimum of 7.5 kg/day for a 500 kg horse). The more forage you can feed the better, so unless you have a good reason for limiting your horse’s forage intake, feed a completely forage diet, balanced for vitamins and minerals. Only use grains or grain-based feeds when absolutely necessary.
Note: If you are concerned about a weight disadvantage in racing and other performance horses due to large amounts of forage being carried in the gut, reduce the amount of forage being fed slightly in the days leading up to a race or event.
2. Feed a variety of forages
Feeding a variety of forages provides your horse’s gut bacteria with a variety of fibre. Fibre variety encourages the growth and development of a more diverse hindgut bacterial population. The bacteria, who as discussed are required for fibre digestion and vitamin production, as well as the regulation of immune function and behaviour, are crucial for your horse’s hindgut health and overall health. When this bacterial population is more diverse it is also more robust, meaning smaller stresses like transport and competition are less likely to cause a negative disturbance to the bacterial population!
To achieve fibre variety, try to use at least a couple of different grass-based hays as well as one or two legume hays (alfalfa/lucerne, clover) and where possible, you can also incorporate ‘novel’ fibres like sugarbeet pulp, lupin hulls or copra meal. Where horses have access to pasture, you should sow or maintain as many different plant species in your pastures as possible.
3. Feed cooked grains or grain-based feeds to prevent grain starch being fermented in the hindgut
Starch fermentation in the hindgut will disrupt bacterial populations, reducing the population of beneficial fibre fermenting bacteria and favouring the undesirable starch and sugar fermenting bacteria. If enough starch is fermented, VFAs and lactic acid will build up, creating hindgut acidosis which can then lead to serious issues like laminitis, endotoxemia and damage to the hindgut wall (hindgut ulcers).
So, if you feed grains or grain-based feeds, always use a cooked product (ie steam flaked, micronized, extruded or boiled) as uncooked grains, with the exception of oats, are poorly digested in the horse’s small intestine and will almost certainly end up being fermented in the hindgut. Oats may be fed uncooked but feed them only in small amounts per meal.
4. Try to avoid high fructan forages
Some forages like oat, wheat or barley forage and ryegrass can contain large amounts of the carbohydrate fructan. Fructan is not digested in the small intestine, but it is readily fermented by the bacteria in the hindgut and, like grain starch, may cause a shift in bacterial populations away from the beneficial fibre fermenting bacteria.
5. Feed in small meals
When feeding grains, never exceed 0.5 kg per 100 kg of bodyweight (0.5% bodyweight) in any one meal, keeping mind this is the maximum. The smaller you can keep meal size the better. Feeding grains in larger meals will make the feed travel quickly through the small intestine and will push undigested grains into the hindgut where their starch will be rapidly fermented.
6. Make sure your horse is drinking enough water
Water intake is crucial for maintaining a healthy hindgut. Dehydration will result in the hindgut contents drying out too much and can lead to problems like impaction colic.
If you live in a cold climate offering your horses warmed water may help to increase their water intake. If you suspect your horse is not drinking enough water, try adding molasses or other flavourings your horse might like to the water. Make sure horses feel safe around their watering point and ensure that they always have access to water and a salt lick. If you are really struggling to get your horse to drink enough, consider adding some salt or an electrolyte supplement to their feed to stimulate thirst. If, however, your horse stops eating its feed, reduce the amount of salt or electrolyte you are giving until you find the amount your horse will eat happily each day.
7. Remove sand and dirt from the hindgut regularly
If your horse is grazing in dry/drought conditions or is housed in a dry lot or sand yard you should feed psyllium husk on a regular basis to remove sand and dirt from the hindgut to prevent it accumulating to the point where it will cause problems.
Feeding 50 grams of psyllium husk per 100 kg bodyweight for 5 days in every one month will help to remove any sand or dirt that may have accumulated in the hindgut. It is particularly important to do this if you horse is receiving restricted amounts of pasture or hay each day.
8. Make all dietary changes slowly
Sudden changes in feed can upset the balance of bacteria in the hindgut or can lead to diarrhoea or colic. Making dietary changes slowly over a period of 7 to 14 days (taking longer for the more dramatic changes – i.e. if you were changing from Timothy hay to a blend of timothy and alfalfa/lucerne hay you could do this over 7 days. If, however, you were changing to a diet that included grains, you should introduce the grains slowly over 14 days or longer depending on how well the horse adapts to the new diet) will help to reduce or eliminate any negative impact of a new diet.
9. Avoid the prolonged use of oral antibiotics
Where possible try to use injectable antibiotics. If your horse does have to be on oral antibiotics, feed as much forage as possible during and following the treatment to maintain an environment in the hindgut that favours the more beneficial fibre fermenting bacteria.
Note: Most ‘probiotics’ have limited usefulness when it comes to repopulating a horse’s hindgut following antibiotic treatment. Many probiotics contain Lactobacillus spp bacteria which are useful for outcompeting pathogenic bacteria but are not really what you want your horse’s hindgut populated with. If you feel it is necessary, discuss the option of nasogastric tubing your horse with a warm slurry made with water and the manure from a healthy horse with your veterinarian.
When you are feeding, always think about the hindgut
When you are making feed choices for your horse you should always be thinking about how what you are feeding will impact the hindgut. The 8 tips listed above will keep your horse’s hindgut healthy so it can continue to provide your horse with a good supply of energy and beneficial vitamins. In addition, immune function will be maintained and the risk of problems like colic, loss of appetite, diarrhoea and abnormal behaviour will be reduced.
The hindgut is so critically important to your horse’s overall health! It is so incredibly important that you look after it!
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Equine Gastric Ulcers: Feeding management strategies to reduce the risk for your horse
Equine gastric ulcer syndrome (EGUS) is a major equine health problem worldwide. Multiple studies have reported an incidence of ulcers in performance horses in excess of 90% of horses training.
Ulcers negatively – and sometimes severely – affect a horse’s ability to perform. They cause pain and discomfort. They may reduce a horse’s appetite which in turn limits its capacity to maintain bodyweight. Gastric ulcers can also possibly lead to the development of vices including windsucking and crib biting.
While gastric ulcers in horses have long been recognised as a major health concern, there is an evident lack of understanding in the horse community about what causes them and how they can be prevented.
Continue reading to find out a little bit more about what gastric ulcers are, how your horse’s stomach functions, and a few little things you can do that will dramatically reduce the risk of your horse’s stomach developing this painful condition.
What are Gastric Ulcers?
Gastric ulcers are lesions that are found in the stomach of horses. The horse’s stomach is made up of 2 major regions, the upper ‘squamous’ area and the lower ‘glandular’ area. Gastric ulcers are categorised by their location in the stomach being either squamous gastric ulcers or glandular gastric ulcers – these are two distinct diseases with different risk factors.
Why do gastric ulcers occur in the squamous or upper section of the stomach?
The horse evolved as a grazing animal and, when left to their own devices, will eat for 17 hours or more per day. This means they are constantly chewing and salivating, and their stomach is always full. Because of this pattern of eating, their stomach never developed an on-off-switch for gastric acid production. The equine stomach secretes gastric acid 24-hours a day, regardless of whether they are actually eating or not.
When you think about this from the perspective of our modern-day horses, it is not an ideal situation. Many horses are now stabled with limited access to free choice forage, or they work, compete, and travel, leaving them in situations where they go for extended periods of time without feed.
When a horse eats it produces saliva and one of saliva’s roles is to buffer the gastric acid in the stomach. So, when they aren’t eating, they aren’t salivating. BUT they are still secreting gastric acid. This results in a pool of unbuffered (and therefore very acidic) gastric fluid accumulating in the lower section of the horse’s now empty stomach.
The lower part of the horse’s stomach was smart enough to protect itself from gastric acids, and, provided it is well-nourished, is able to produce enough sticky mucous to protect itself from its own acid secretions. BUT, the upper part of the stomach doesn’t have this same protection. In a grazing horse, the stomach is always full, so the top of the stomach was never exposed to gastric acid simply because the forage a horse ate stopped the acid from ever splashing up there. However, in modern-day, meal-fed horses, the stomach is often empty, and the upper section of the stomach is left totally exposed to the highly acidic fluids that are allowed to accumulate in empty stomachs.
When a horse with an empty stomach trots, canters, gallops, or even simply tenses up its abdominal muscles the gastric fluids are splashed or squeezed up onto the unprotected upper section of the stomach. Simply put, the acid starts to burn holes in the stomach wall lining. If you allow this to occur repeatedly, the horse will eventually develop ulcers. This can happen in just a matter of days.
What major factors influence the risk of squamous gastric ulcers?
The following situations have been identified as factors that can influence the risk of squamous gastric ulcers:
Low forage intake – Not having free access to forage and not being provided with additional forage increases the risk of squamous ulcers (Gehlen et al., 2019).
Feeding Frequency – Feed deprivation such as might occur during transport and long periods between meals lowers the pH in the equine stomach and allows the stomach to empty, both of which will increase the risk of gastric ulceration (Murray, 1994).
High starch diet – Horses receiving large proportions of grain (or starch) in their diets are at increased risk of squamous ulcers (Gehlen et al., 2019). One study shows that a reduction in dietary starch resulted in a decrease in squamous ulcers (Böhm et al., 2018).
Exercise – As a horse exercises, the pressure inside the stomach increases, which forces the highly acidic gastric contents from the glandular area up into the unprotected squamous area (Lorenzo-Figueras et al. 2002). Horses in training are known to have a higher incidence and also more severe gastric ulceration than horses not in work. Similarly, the intensity of long-duration exercise also increases the risk and severity of squamous ulcers in both Thoroughbred racehorses (Murray et al., 1996) and endurance horses (Tamzali et al., 2011).
How can feeding management reduce the risk of squamous ulcers?
Some feeding management practices that may help reduce the incidence of squamous ulcers are:
Don’t exercise horses on an empty stomach – Providing 1-2kg of lucerne hay prior to exercise helps to prevent acidic contents from the lower region of the stomach from splashing up onto the upper region where it can cause squamous ulcers. The saliva created while chewing the hay also helps to buffer the acidity in the stomach. Using lucerne hay has the extra positive benefit with the buffering effect from the high content of protein and calcium in lucerne itself. If you don’t have or feed alfalfa (lucerne) hay, then your horse’s regular hay will also work well.
Provide constant access to pasture or hay – Allowing the horse to feed continuously during the day and night will help to reduce the likelihood of squamous gastric ulcers developing. However, free access to forage does not always guarantee your horse is eating enough forage. For example, overgrazed pasture (<2.5cm or 1 inch in height) does not provide adequate amounts of fibre to protect the stomach. Likewise, providing free access to a round bale does not guarantee your horse is consuming adequate amounts. This may be due palatability of the hay or an already depressed appetite from gastric ulcers. Horses need to be consuming at least 1.5 to 2% bodyweight in forage per day. Providing supplementary hay to horses on pasture and feeding a set amount of hay per day is the easiest way to ensure adequate intake.
The importance of constant access to adequate amounts of forage ensures good amounts of saliva being produced by chewing, which has a buffering effect on stomach acid, and fibre’s ability to create a ‘ball’ in the stomach to limit acid splashing. If horses need to go periods without access to forage or having a feed, this should be limited to no more than 5 hours.
If you are travelling long distances with your horse, and it is safe to do so, providing hay in a hay net during travel will provide the horse with an opportunity to continue eating during transport. If this is not possible, take regular breaks and provide small forage meals during the trip.
Reduce starch in feeds – Reducing the amount of starch in the diet by reducing or removing grain-based concentrate from feeds is recommended. Due to the different starch content of various grains and feeds, maximum intakes are based off starch intake. No more than 1 gram of starch per kilogram of bodyweight per meal should be fed and maximum of 2 grams of starch per kilogram of bodyweight per day. For example, barley contains on average 60% starch. For a 500kg horse, the maximum amount of barley which should be fed is 800g per meal or 1.6kg per day split over two meals, which is the equivalent of 480g of starch per meal.
For horses requiring a high energy diet, grain-based feeds can be substituted with a combination of high energy fibre such as alfalfa pellets, chaff or alike, beet pulp, soybean hulls, and high fat ingredients such as oilseeds and oils.
What about Glandular ulcers?
The following situations have been identified as potential risk factors for glandular ulcers:
Exercising more than 4 days per week – Exercising 5 or more days per week was a key risk factor for glandular ulcers in Thoroughbred racehorses (Sykes et al., 2019). Another study showed that increased days in work (up to 6 days per week) and actively competing are risk factors in Warmblood showjumpers (Pedersen et al., 2018). The prevalence of glandular ulcers doubles in in endurance horses during competition season (Tamzali et al., 2011). It’s not clear why exercising for 5 or more days per weeks increases the risk of glandular ulcers, although it is hypothesised that during exercise there is a decrease in blood flow to the stomach (Rendle et al., 2018).
Stress – an increased prevalence has been observed in domesticated horses compared with feral horses (Ward et al., 2015). This suggests that intensive management plays a role in the increased risk of glandular ulcers in horses. Stabling or confinement, lack of contact with other horses (individually paddocked), and having multiple handlers or riders can all increase risk.
How can feeding management reducing the risk of glandular ulcers?
Diet does not appear to a key risk factor but does form part of the management of horses at risk of glandular ulcers. One study looking at the effect of diet composition on glandular ulcers does support this (Julliand et al., 2023). Some of the key findings of this study were:
Horses allocated to the non-ulcerated group had a higher daily intake of simple sugars in their pre-Day 0 diet (same diet for 4 weeks prior to Day 0) than horses in the ulcerated group.
Horses which remained on the full rate of grain concentrate did not show improvement in glandular scores over the 42-day study period. In fact, the number of horses with glandular ulcers greater than 2, increased over the study period.
Five out of six horses that had half their grain concentrate substituted with alfalfa pellets showed improvement in their glandular scores from greater than 2 to scores of 0-1.
Some feeding management practices that may help reduce the incidence and severity of glandular ulcers are:
Reduce starch in feeds – This is beneficial for reducing the fermentation products in the gastric contents which, when combined with a very acidic environment, cause damage to the glandular mucosa.
For horses requiring a high energy diet, this can be achieved by substituting grain-based feeds with a combination of high energy fibre feeds like beet pulp, soybean hulls, etc and high fat ingredients such as oilseeds and oils.
Include alfalfa (lucerne) in feeds – Inclusion of alfalfa (lucerne) pellets, chaff or alike 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.
In the above-mentioned study, horses receiving approximately 5-6kg of grain concentrate per day transitioned to a diet of approximately 3kg grain concentrate and 2.8kg of alfalfa pellets per day. As a guide, inclusion of 2-2.5kg of alfalfa (lucerne) pellets or alike to feeds may be beneficial.
If your horse already has gastric ulcers, you must treat them
While one study has shown that feeding lucerne hay can reduce the severity of ulcers already present in horses and long periods of pasture turnout will sometimes allow a horse to resolve gastric ulcer issues, if your horse already has gastric ulcers, treating them with veterinary prescribed medication is important for a quick resolution. Talk to your veterinarian about the best treatment regime for your horse.
Finally …
Gastric ulcers are a serious and common health problem in horses that will affect their overall wellbeing and performance. While we still don’t have a full understanding of how and why they occur with such a high incidence, using the feeding and management strategies outlined above will help to reduce your horse’s risk of developing gastric ulceration.
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!
