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!
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!
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.
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!
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.
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!
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.
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!
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!
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!
