Starch & Ulcers: What’s The Deal?

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

Starch is fermented to volatile fatty acids (VFAs)

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

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

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

Lucerne + grain = less ulcers than grass hay

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

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

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

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

What about high fibre versus low fibre?

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

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

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

How much starch is OK?

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

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

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

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

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

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

Does starch cause ulcers?

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

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

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

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

 

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

 

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

Should I go grain-free?

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

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

References

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

 

Dr. Nerida Richards is FeedXL’s resident equine nutrition specialist. With 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 Nerida is able to help FeedXL members solve any problem they may come up against with feeding their 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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The Gastrointestinal Tract: The Key to Feeding Your Horse

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.

It is absolutely critical to keep the hindgut healthy. For more information on the hindgut and how to keep it healthy, read our FeedXL Newsletter #15 – 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:

  • 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.

 

Dr. Nerida Richards is FeedXL’s resident equine nutrition specialist. With 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 Nerida is able to help FeedXL members solve any problem they may come up against with feeding their 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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Keeping the Hindgut Healthy

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.

8 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 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. Make all dietary changes slowly

4horses

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.

8. 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!

 

Dr. Nerida Richards is FeedXL’s resident equine nutrition specialist. With 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 Nerida is able to help FeedXL members solve any problem they may come up against with feeding their horses. To learn more about Nerida and to ‘meet’ the rest of the FeedXL team, check out our About Us page here.

QUESTIONS? COMMENTS?

Click here to join our Horse Nutrition Forum on Facebook

Avoiding Gastric Ulcers in Horses

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 a 90% incidence rate of ulcers in performance horses.

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 and they possibly lead to the development of vices including windsucking and crib biting.

While gastric ulcers have long been recognised as a major health concern there is an evident lack of understanding in the horse owning 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. The majority of ulcers in adult performance horses occur either in the squamous area or at the junction of the squamous and glandular regions.

Why do gastric ulcers occur in the 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. So their 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. In modern day, meal fed horses however, 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. The acid simply 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 factors influence the risk of gastric ulcers in horses?

Gastric ulcers are a ‘multi-factorial’ disease, meaning they are caused by many things. The following situations have been identified as factors that can influence the risk of gastric ulcers:

  1. Exercise on an empty stomach – 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). Exercising horses on a close to empty stomach (as would be the case in horses exercised after an overnight fast) makes it is easy for the acidic contents of the stomach to be pushed up into the squamous upper region of the stomach where it can cause ulceration.
  2. Training – horses in training are known to have a higher incidence and also more severe gastric ulceration than horses not in work. In has been reported that the risk of developing moderate to severe gastric ulceration increased 1.7 times for every week that a horse was in training (Lester et al. 2008).
  3. Training location – in thoroughbreds, horses that were exercised on a track on the property where they lived had 3.3 times less chance of having gastric ulcers (Lester et al. 2008).
  4. Turnout/paddock time – horses that were given access to some turnout time were less likely to develop ulcers (Lester et al. 2008).
  5. Turnout time with paddock mates – horses turned out with other horses are even less likely to develop ulcers than horses turned out alone (Lester et al. 2008).
  6. Stress/nervousness – talkback radio playing in stables was found to increase the likelihood of thoroughbred horses developing ulcers, suggesting stress is a risk factor for ulcers (Lester et al. 2008).
  7. Forage type – alfalfa (also known as lucerne) hay appears to have a protective effect on the equine stomach and appears to reduce the incidence of gastric ulcers in horses (Nadeau et al. 2000; Lybbert 2007).
  8. 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).
  9. Non-Steroidal Anti-inflammatory Drugs (NSAID) – drugs like phenylbutazone have been shown to increase the risk of ulcers, particularly in the glandular (lower) region of the stomach.

How to reduce the risk of gastric ulcers in horses

To reduce the risk of gastric ulcers you need to assess your horse management systems and make changes wherever your horses are exposed to one of the above risk factors. Some feeding management practices that may help reduce the incidence and severity of gastric ulcers are:

Don’t exercise horses on an empty stomach

Providing a small meal of alfalfa (lucerne) hay prior to exercise will:

1. Help to stop the acidic contents from the lower region of the stomach from splashing up onto the upper region where it can cause ulcers;
2. Provide a buffering effect by causing the horse to produce saliva while it is chewing the hay and through the buffering effect of alfalfa hay itself. If you don’t have alfalfa hay then your horse’s regular hay will also work well.

To learn more about what happens when you exercise a horse on an empty stomach, click here to read our post (and watch the video) on ‘Why You Should Never Ride Your Horse on an Empty Stomach’. 

Provide a small meal of alfalfa (lucerne) hay immediately following exercise

The Western Australian study which found horses trained off site had a higher incidence of gastric ulcers suggests that the time taken to return home following training and thus time between the completion of training and breakfast and perhaps the stress associated with travelling is increasing the incidence of ulcers. Providing a small meal of alfalfa following training will again help buffer the horse’s stomach and protect it from gastric ulceration. Again if you don’t have alfalfa hay your horse’s regular hay will help.

Provide turnout time (with paddock mates where possible) as often as possible

Paddock turnout will help to reduce a horse’s stress level and if pasture is available will provide the horse with an opportunity to graze, and thus continuously produce saliva to help buffer the stomach and to keep their stomach full.

Provide regular small meals and constant access to hay

Allowing the horse to feed continuously during the day and night will help to reduce the likelihood of gastric ulcers developing. Divide the horse’s daily concentrate ration into as many meals as you can to be fed during the day and evening and provide hay at all times (preferably not all as alfalfa hay, some grass hay will provide variety in the diet and keep the horse’s protein intake in check).

If you are travelling long distances with your horse take regular breaks to provide small meals during the trip. Providing hay in a hay net will also provide the horse with an opportunity to continue eating during transport. Just beware of dusty hay increasing the risk of travel-sickness and the of course the risk of entanglement in the net. If you are traveling with your horse over long distances on a regular basis, consider using a gastric ulcer medication (omeprazole or ranitidine) just prior to and during travel to cut the acid production and reduce the risk of ulcers. Speak with your veterinarian about this.

If you are concerned, with feeding a lot of hay, about your horse’s gut fill leading into a competition, you can reduce the amount of hay you are feeding for 2 days leading up to an event. However be careful not to reduce total forage intake to less than 1.5% bodyweight per day.

Using these feeding management strategies in combination with strategies to reduce stress will help to reduce a horse’s risk of developing gastric ulcers.

If your horse already has ulcers you must treat them

While one study has shown that feeding alfalfa (lucerne) hay has been shown to 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 ulcers you must treat them with a registered ulcer treatment (omeprazole or ranitidine). Talk to your vet 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. If you remember nothing else, just remember this… never work your horse on an empty stomach!

 

Image provided by RandLab (https://www.randlab.com.au)

Dr. Nerida Richards is FeedXL’s resident equine nutrition specialist. With 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 Nerida is able to help FeedXL members solve any problem they may come up against with feeding their 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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