In this article, Dr Emanuela Valle a researcher and veterinary consultant in Torino, Italy, explains the role of diet and behaviour in the prevention and management of equine gastric ulcers.
Despite thousands of years of domestication, the horse you own today is not that different to its wild ancestors. Over time, our selective breeding approach has mainly targeted conformation characteristics and suitability for the different work we required. However, the horse’s physiological and behavioural characteristics are virtually unchanged. This means that your horse is essentially an herbivore whose main focus in life is foraging in an accurate and targeted way.
Forage, friends and freedom
It is no coincidence that when we let our horses out on grass they put their heads down and often don’t stop grazing for several hours.
In nature, a horse grazes on average 15-16 hours and, in special situations, sometimes 19 hours. This means that feeding is an important moment for the horse. All of its behavioural and physiological features have evolved to better manage his way of life. In the wild, a horse’s diet is rich in fibre and grazing is the main source of forage.
A diet rich in fibre has been shown to affect the production of hormones such as serotonin, known as the ‘wellbeing hormone’.
Gut-Brain: essential for wellbeing
In the horse, there is a strong primordial axis or ‘gut-brain’, which is essential in the maintenance of wellbeing. The French saying ‘Tout le cheval est dans son intestin’ (the whole horse is in his gut) shows that horse people have always known how important this relationship really is. The saying emphasises the ancestral and indissoluble link between the horse’s health and good dietary management.
Providing a proper diet means devising a holistic plan that fulfils your horse’s nutritional needs as well as the characteristics of his or her anatomy, which are:
- A stomach made to accommodate small amounts of food continuously throughout the day, unable to accept large meals because of its small size, as well as its inability to vomit.
- A very long and tortuous small intestine where the secretion of enzymes to aid with starch digestion is limited.
- A highly-developed large intestine (hindgut) dedicated to the fermentation of fibre and which, anatomically, has considerable variations in diameter, such as the passage from caecum to the colon or from small intestine to the large colon.
You need to be clear about these anatomical characteristics if your aim is to provide optimal management and reduce the incidence of health problems.
Basic facts on ulcers
Equine Gastric Ulcer Syndrome (EGUS) is an important and frequent problem, and has been attributed to high intensity exercise, but incorrect feeding practices should not be underestimated.
EGUS is referred to as a ‘syndrome’ rather than a disease, because it has several causes and a complex nature. Recent studies suggest that EGUS is extremely common and not just found in horses that are in intensive training.
Thoroughbred racehorses have shown a 90% incidence of EGUS, whilst some studies report 37% of horses used for light or recreational activities have gastric lesions, irrelevant of discipline.
Certain events, such as transport or a simple stay at a competition venue, have been shown to trigger the conditions that result in the formation of gastric ulcers.
Horses at pasture, such as broodmares and foals, have also been reported to suffer from ulcers even if they are not intensively managed.
All these statistics suggest it is not just the activities or level of exercise you and your horse do that are important.
Predisposing factors for EGUS have been shown to be related to inadequate management of nutrition, training, transport, changes to the environment, meal feeding, use of specific drugs, social and behavioural stress.
The equine stomach's anatomy and physiology
Understanding the reasons why any of the above predisposing factors can act fairly quickly and result in ulceration is easier when you study the very particular physiology and anatomy of the horse’s stomach. (See the anatomical illustration by downloading the pdf version of this article).
The stomach of the horse is a relatively small organ where it is possible to identify two different parts: the non-glandular stratified squamous mucosa and the glandular mucosa. The transition area that delineates the border between the two parts is called margus plicatus.
Ulcers or lesions could be located in either part of the stomach, but their causes can be different.
The non-glandular mucosa is not designed to produce nor handle the gastric juices composed of clorhydric acid and enzymes to digest proteins; it is not protected against these factors.
On the other hand, the glandular mucosa is protected by a thick layer of mucous and bicarbonate buffers that prevent the gastric juice from affecting the stomach wall. This is why there are several risk factors for the formation of an ulcer.
In the non-glandular mucosa, the lesions are mainly due to exposure to the highly acidic gastric juice. Whilst the glandular mucosa lesions are essentially due to the decrease or failure of the mucosa’s defences. Most frequently, lesions are located in the squamous mucosa just near to the margus plicatus.
In nature, horses are virtually continuous grazers. They generally spend no more than three to four hours without feeding.
This means that the stomach almost always contains food and, for that reason, they constantly secrete gastric juice. When confined, their natural feeding pattern is normally altered, both in meal schedule and composition.
Many times, horses experience sustained fasting; The 500kg horse that receives his last meal of 4kg hay at 6pm and has to wait for breakfast at 6 or even 8am the next day with no other forage available. This horse is going to have an empty stomach for many hours.
When food is not available, the pH in the stomach becomes very low (acidic). Why? Because the saliva’s buffer is not present and there is no food in the stomach.
Fibrous forage forms a ‘mat’ between the mucosa and the acid, and contributes to the dilution of gastric juices.
If your feeding schedule provides intermittent periods of food and quite long periods of fasting, the non-glandular mucosa is easily exposed to acidic conditions.
In comparison, a horse with unlimited access to forage has a higher (more neutral) stomach pH, therefore, lowering the amount of acid.
As you can see, forage is absolutely essential to your horse. When your horse receives forage, he produces more saliva. A horse that receives 10kg of hay can produce at least 35 litres of saliva, whereby a horse on a diet of concentrates with very low levels of forage, produces less than 20 litres of saliva. The action of chewing stimulates the production of saliva that is rich in a bicarbonate buffer that dilutes the effect of acid in the gastric juices.
The risks of concentrates
A concentrate-based diet with reduced forage availability increases the risk of ulcers, due to a lack of adequate chewing time. The long periods of fasting (especially longer than six hours) associated with most high-starch diets cause an increase in the volatile fatty acids produced in the stomach by the fermentation of bacteria, like Lactobacillus and Streptococcus which, in turn, contribute to lesions in the mucosa.
Minimum roughage quantity
A horse requires a minimum of between 1-1.5kg of roughage per 100kg bodyweight. Ideally though and considering the time it takes to consume, it should be closer to between 1.8-2kg of forage per 100kg bodyweight.
This means that a horse weighing 500kg should receive 9-10kg of forage spread throughout the day. Splitting the daily intake of roughage into several feeds and using feeding systems designed to slow down intake and prolong chewing times, also helps maximise chewing times and saliva production.
Good-quality meadow/grass hay (cut from a biodiverse pasture) is a good choice for horses. The nutritional value of the hay we choose can only be established through laboratory testing, and this is invaluable in order to ensure the horse’s nutritional requirements are met in accordance with his body condition and exercise level.
Alfalfa hay or lucerne is a good addition to the diet of horses diagnosed with EGUS, because the high levels of calcium and proteins act as a buffer.
However, and also due to its high level of calcium and protein, lucerne hay should be limited to maintain the mineral balance of the diet.
Wheat straw is not a suitable forage choice for horses, as it could have less buffering capacity and often has a high level of lignin that could contribute to a mechanical irritation of the mucosa.
Grain meals warnings
Grain-based concentrates should be used with care as we know that a high dietary starch intake is deleterious for the stomach and for the hindgut.
A horse’s diet should not exceed more than 1 gram per kilo of bodyweight of starch per meal. That means that a horse weighing 500kg should not be fed more than 500 grams of starch per meal (approximately 1.2-1.4kg of a grain-based mix per meal).
The total quantities of concentrates fed daily should actually be calculated based on the real needs of the horse. An excess not only predisposes your horse to EGUS, but also to obesity and/or laminitis. Consider also adding chaff to your grain-based meal to help increase chewing and saliva production.
Splitting the forage and concentrate meals of confined horses throughout the day helps them avoid long periods of fasting, ensure enough time is spent chewing and producing saliva, buffering the pH of the stomach and maintaining regular bowel motility.
The paddock effects
Grazing on pastures for as many hours a day as possible is a remedy for the horse’s mind and the gut. Outside in the paddock horses have the chance to socialise, relax and engage in their favourite activity, grazing.
Despite all this, we know that horses kept 24/7 on pasture can also have ulcers, so it is important that horses can graze on good-quality, biodiverse grasses, that they can also access hay of suitable quality for their particular needs and, of course, have freely available fresh water.
Drugs and supplements
Some studies have reported that horses who are regularly administered electrolyte pastes (such as endurance horses) could experience a greater incidence of ulcers.
The recommendation, therefore, is to use these supplements only when required, and to mix them into a high fibre feed or water instead of administering them directly into the mouth.
Some drugs, and especially NSAIDs such as ‘Bute’, should be used for the shortest periods and only according to veterinary advice. NSAIDs have been reported to induce ulceration, this is because they inhibit the formation of some substances that protect the stomach mucosa and they increase the acid production.
What can you do?
The management of your horse should be based on the natural behaviour and physiological needs of horses. This is the only way to avoid physical and psychological stress that can harm your horse’s wellbeing.
A good nutritional plan is fundamental to manage and prevent EGUS but it is not the only factor. Transport, competition, training and drugs, such as NSAIDs, are some examples of risk factors involved in the onset of the problem.
When formulating your nutritional plan for a stabled horse ask the help of a nutritional expert because feeding is complex and mistakes are common.
Signs your horse may have EGUS
- Has lost weight and has difficulties maintaining a good body condition.
- Has a dull and rough coat.
- Has poor appetite.
- Displays reduced performance and different results both in training or competition.
- Shows a change in attitude and behaviour, e.g. suddenly displaying out of the ordinary flight or fear responses or has become very dull or too calm.
- Has recurring bouts of colic with mild pain.
- Abdominal pain can also be shown by frequent stretch to urinate or excessive recumbency (lying down).
- Crib-bites - Studies have shown this stereotypic behaviour is frequently associated with gastric ulcers.
- Grinds his/her teeth (bruxism).
What if you horse has EGUS?
If you suspect your horse has EGUS, consult your veterinarian about the diagnosis and treatment option that are available and aim to provide:
- Optimal management in the form of freedom, forage and friends. And this goes for all horses!
Optimal management is about putting the needs of the horse first.
Your aim should be to provide your horse with unrestricted movement, access to forage and friends, as well as a training program that aligns with the correct application of learning theory to reduce your horse’s exposure to stress and optimises his or her physical and mental wellbeing and performance.