Gastric disease – how should we treat it?

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The relationship between starch intake and gastric ulcers

Digestive Aids - what is available to racehorses?

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Dr Catherine Dunnett (16 July 2009 - Issue Number: 13)

Digestive Aids - what is available to racehorses?

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(European Trainer - issue 26 - Summer 2009)

Equine gastric ulcer syndrome

Equine Gastric Ulcer Syndrome (EGUS) is an increasingly common problem in the Thoroughbred racehorse, causing a range of symptoms from depression to aggression, and often impacting negatively on performance.

Diagnosis is sometimes difficult, although there are methods by which they can be swiftly identified and treated. Equine gastric ulcers are graded on a scale of 0 to 4 where 4 is the most severe. A grade of 2 or more is clinically significant and usually warrants treatment. The primary objectives of treatment of equine gastric ulcers are to facilitate healing and relieve symptoms.

This can be accomplished by the use of antacids, histamine receptor antagonists or acid pump inhibitors. Ulcers are an issue - especially for racehorses- as they can be a source of chronic pain, leading to reduced appetite, loss of condition and sometimes colic. The clinical signs of the problem are often intermittent, and can vary tremendously depending on the horse and the types of discipline they compete in.

Two types of tissue line the equine stomach. The bottom of the stomach is lined with a pink glandular mucosa which constantly produces concentrated hydrochloric acid, whilst protecting itself with a sticky mucus and bicarbonate secretion.

At the top, the squamous (or non-glandular) mucosa is found – this tissue has no useful role in the stomach as it does not produce acid nor any protective mucus - squamous mucosa is therefore very susceptible to acid injury.Racehorses are more prone to ulcers in the squamous mucosa.
 


A pairing of equine vets that regularly diagnose and treat equine gastric ulcers are Rachael Conwell and Richard Hepburn, who are based in England. Hepburn estimates that 80% of ulceration is found in the top part of the stomach and Conwell's experience in practice also supports this. She explains: "With increasing intensity of exercise, it is thought that acid splashes up to cause ulcers in the squamous region.

This can vary from low grade to quite significant degrees of ulceration". "Quite often there can also be glandular ulcers at the exit from the stomach into the duodenum so it's important to look here," says Conwell.

Hepburn explains: "Horses may exhibit poor exercise tolerance, be reluctant to gallop and have slower race times. Post-race heart rates are higher when ulcers are present." Conwell adds: "A problem with ulcers is that they can manifest as low grade colic or failure to maintain bodyweight, particularly in racehorses." They may also have reduced exercise tolerance, refuse to gallop, and have poor jumping performance.

Poor coat hair can be another indicator. "Generally trainers are pretty good at spotting the signs. They may notice that feed doesn't get cleaned up in quite the usual hungry way. They also know their horse's character and so will notice small changes in attitude. The horse might become more grumpy, look miserable, resent being groomed or having their girth done up.

Perhaps they are just not the happy horse they used to be. It can be as subtle as that."  "In some situations there are no outward signs at all, only that the horse's performance is reduced." Says Conwell. 

According to Hepburn, the incidence of EGUS may be up to 100% in racehorses, with ulcers most severe in horses that are in full training or have just raced. 
Conwell and Hepburn regularly use gastroscopy as a method of ulcer detection. Gastroscopy is a visual examination technique through which a veterinarian will assess the stomach health of an animal using an endoscope, determining the presence and severity of ulcers and monitoring the success of prescribed treatment. Moreover it is a non-surgical and relatively simple procedure which takes less than fifteen minutes.

The same kit can also be used for airway examinations looking at the larynx, trachea and bronchi for respiratory problems, and inside the guttural pouch to check for infections such as strangles. This is useful as it means horses do not need to be sedated on more than one occasion to assess both airway and stomach health. 

Using gastroscopy to diagnose ulcers is a relatively simple procedure. The horse is starved for 8 hours but is allowed free access to water. It is then given a short acting sedative, and an endoscope is passed up the nose, down the esophagus and into the animal's stomach.

The stomach is inflated with air using a pump attached to the endoscope and any food is washed off with water- squirted through the endoscope. Once the end of the endoscope is in the stomach, it can be ‘driven' by the vet using hand-held controls to move it up or down, to the left or right. In this way the inside wall of the entire stomach can be examined.

A key difference between regular endoscopy and the specialist gastroscopy kits now available is that there is 3m of length to enable full examination of the entire stomach. Endoscope diameter is another difference, with 9 or 11mm being better tolerated by the horse for gastroscopy work than the standard size of 13mm.

Conwell has been using a 3m video-endoscope for two years now for diagnosing and treating racehorses. She says "I don't normally scope all horses in a training yard, only the ones where there is a suspicion that gastric ulcers could be affecting them. That said, it's rare that we don't find any ulcers in the racehorses we investigate." 

Other methods of detecting ulcers within the digestive system, anywhere from the stomach to the intestinal tract, are also proving effective. Kits which allow the handler to test for blood in the feces of the horse, an indicator of possible ulceration, are becoming more widely available, and may be a cheaper and less invasive method of diagnosing digestive health issues. 

In treating gastric ulcers, most vets will turn to a licensed acid suppressant product for equine use.

Treatment will vary in duration and intensity depending on the individual case, taking into account a number of factors including severity of ulceration and importantly, the horse's training regime, as there is some evidence that treatment effectiveness of some medications vary when the horse is still in full work. Antacids (which neutralize acids in the stomach), omeprazoles in paste and suspension (which suppress acid production) and histamine receptor antagonists are commonly used to reduce symptoms, heal lesions and reduce the likelihood of future problems.

Acid suppressants fed once a day are an effective remedy, believes Conwell, who adds: "Alternatively, histamine receptor antagonists, such as ranitidine, can be used. I normally re-scope horses about four weeks after treatment. If the problem has resolved then I recommend a quarter dose of an acid suppressant to prevent recurrence of ulcers during training." 

Trainers often notice a character change in their horses once treatment is started, according to Conwell.

Hepburn reports that some owners are ‘amazed' at the difference in horses given treatment for their ulcers: "Even though they may have been performing well before, resolving the problem makes their performance consistently good."

In addition to prescribing medication, ulcers can be reduced and in some cases, totally resolved by changing the feeding and/or stabling routine. High grain diets and a limited access to forage - which buffers stomach acid - are a factor in the prevalence of EGUS in racehorses. Ideally, horses should be given more access to a selection of forages, just as they would in the natural wild.

Conwell and Hepburn both recommend putting several haynets up, some with hay and others with haylage, to allow the horse to browse for forage. 
Hepburn says: "Turning horses out every day may help, although ulcers are just as common in NZ racehorses that are trained from pasture. Interestingly, some ongoing Danish work has shown that giving horses the choice of staying in or going out can reduce stress and associated gastric ulceration."

Various feed supplements are also available which help to maintain digestive health, both in horses which have received treatment for ulcers and are recovering, and in horses showing no symptoms of ulceration, in order to lessen the chance of digestive problems.

This is especially useful where it is not possible to radically change management practices, such as with horses stabled at the racetrack.
Hepburn concludes: "Some horses are more prone to ulcers than others – hence the need to assess each individual case. Also some ulcers heal more quickly depending on their location in the stomach."

Rachel Queenborough
 (10 July 2008 - Issue 9)

Equine Gastric Ulcer Syndrome

Vets and other professionals recognise that gastrointestinal function and health in horses exists in a finely balanced state. Most conditions relating to the intestinal tract, for example colic and diarrhoea are well understood and are most commonly treated either medically or surgically. There has been, however, less appreciation of how frequently the health of a horse’s stomach can be compromised. The true prevalence of equine stomach lesions (gastric ulcers) was recognised only with the introduction of gastric endoscopy. How prevalent are ulcers? Numerous studies conducted in the 1980s and ‘90s in varied horse populations within differing sporting disciplines identified EGUS as a much more a widespread problem than commonly assumed. Many of these studies focussed on thoroughbred racehorses, and produced remarkably similar findings.

Between 80 and 90% of horses in training were found to have gastric ulcers. And, somewhat surprisingly, over 50% of racehorses temporarily out of training also had lesions. Moreover, this health and welfare issue was not confined to thoroughbred racing; horses competing in other equestrian sporting disciplines were also prone to this condition. In contrast, less than 5% of permanently grazed horses appear to suffer from gastric ulceration. Prevalence of EGUS in horses engaged in different equestrian sporting disciplines Population Prevalence (%) Racing (thoroughbreds) 80 - 90 Trotting/pacing (standardbreds) 72 - 88 Endurance racing 67 Show horses 58 Foals (thoroughbred) > 50 Symptoms to look for that may suggest gastric ulceration include chronic recurrent colic, episodic colic, acute colic, reduced appetite, poor body condition and chronic diarrhoea. Whilst these clinical signs are not always indicative of gastric ulcers, as can be seen from the table below there is a clear relationship.

The strongest indicator appears to be an inability to thrive as indicated by poor body condition and reduced appetite. Incidence of overt clinical signs in horses subsequently found to have EGUS Clinical signs Incidence (%) Chronic recurrent colic, for 7 days or more 25 Episodic colic (1+) for 7 or more days 13 Acute colic 10 Reduced appetite 53 Poor body condition 40 Diarrhoea 9 Unfortunately, however, in about 52% of horses where gastroscopy reveals ulceration there will have been no obvious prior clinical signs.

What causes gastric ulcers? Gastric lesions (ulcers) are now recognised as a common condition in stabled horses, whether involved in racing or other equine sports, and in foals, yet they appear to be absent in wild horses. You may be familiar with the fact that gastric ulcers in humans are frequently caused by infection with a bacterium called Helicobacter pylori, it was not surprising therefore that this was investigated but then dismissed as a possible cause in horses. So, what is the cause and why is the prevalence in racehorses so high? To answer this question we need to examine the manner in which we train, house and feed our racehorses. All the clinical evidence to date indicates that the high incidence of gastric ulcers in racehorses is a ‘man-made’ phenomenon that is related to the feeding and management practices that we employ during training.

There are four key contributory factors involved in the development and progression of ulcers:

1) Dietary makeup and feeding practices

2) Intensity of exercise (level of work)

3) Stress factors

4) Prolonged use of non-steroidal antiinflammatory drugs, such as phenylbutazone, and corticosteroids. When considering these factors we need to appreciate that the horse has evolved over millennia as an exclusively grazing animal with a digestive system that is reliant on the continual ingestion of fresh forage to meet its dietary requirements. In EGUS the damage caused to the lining of the stomach arises from prolonged exposure of the gastric mucosa to gastric acid, without sufficient protection from the buffering effect of saliva.

Dietary makeup and feeding practices Racehorses are most often fed a diet that is high in starch rich cereal and low in forage. Horses produce gastric acid continuously, and high starch diets tend to further increase its production through stimulation of a hormone known as gastrin. In addition, where these starch-rich meals are large, inadequate mixing in the stomach can lead to some of the starch being fermented here, which further contributes to the overall acidity. During feeding, chewing normally stimulates the production of saliva, which contains a natural buffer ‘bicarbonate’, to offer some protection of the gastric mucosa against the corrosive effects of gastric acid. However, the amount of saliva produced for each kilogram of concentrate feed consumed is about 2.5 times less than that produced for the same weight of forage, as proportionally less chewing is involved. Minimal forage intake therefore takes its toll on gastric health, as during periods when the horse has no access to feed or forage, the protective effects of saliva are lost and these are key danger times for gastric ulceration.

A recent study published in the Equine Veterinary Journal also suggests that repeated electrolyte or salt administration may exacerbate or even induce gastric ulceration. But before we all cast aside our daily electrolyte or salt administration, which has great physiological benefit, we need to take these recent findings in context. This latest study used an endurance model of electrolyte administration using a concentrated electrolyte syringe 8 times within an 8-hour period. Whilst this may be common practice during endurance races, this type of administration in racing is in my experience not practised. It is, however, a difficult conundrum for endurance trainers as electrolyte depletion during races is a significant issue.

Certainly electrolyte or salt products that dissolve more slowly in the stomach may be an advantage. Exercise intensity The level of work that horses undertake has also been found to be a significant contributory factor in the development of EGUS. Although ulcers are present in about 40% of horses undertaking light exercise this increases to over 95% in horses with busy racing schedules. This effect probably arises through the physical movement of the organs and tissues within the horse’s body that occurs during exercise. Mechanical movement and compression of the stomach forces the most sensitive non glandular regions of its lining into further contact with gastric acid, and this effect is exacerbated when exercise intensity is increased.

Stress Although training and racing by necessity place horses under physiological stress, psychological stress is also implicated in ulcer development. Recent studies in the USA indicate that sudden stressful changes from the normal daily routine and environment, including transport and new stabling, promote rapid changes to the integrity of the stomach lining. Indeed, gastroscopy showed the appearance of ulcers within only 6 days. Medical treatment of gastric ulcers Gastric ulcers in horses rarely heal spontaneously, so veterinary intervention is necessary. Methods for the treatment and prevention of gastric ulcers in horses follow those employed in human medicine and generally involve the use of antacids alone, or in conjunction with anti-ulcer drugs.

Antacids neutralise gastric acid. Those based on sodium and calcium carbonates and bicarbonates have the potential drawback of releasing carbon dioxide (gas) in the gut. In addition, bicarbonate supplementation can increase blood bicarbonate levels that could potentially result in a breach of doping rules. Antacids containing aluminium or magnesium hydroxides and silicates may be preferential.

Drugs used to inhibit gastric ulcers include, the H2-receptor blockers cimetidine and ranitidine and the so-called ‘proton-pump inhibitor’ omeprazole. Omeprazole is the most widely used and effective treatment in horses and is marketed as an oral paste under the trade name Gastroguard. Dietary supplement products available for gastric health Product Company Active ingredients Function Product Form Dose (500kg horse) Neigh-Lox Saracen (KER) Dihydroxy-aluminium, sodium carbonate, calcium carbonate, aluminium phosphate Antacid Coats & protects Pellet 340g Settlelex Feedmark Calcium carbonate, aluminium hydroxide, magnesium carbonate, dicalcium phospahte Antacid Powder 30-100g Acti-Soothe Nelson Veterinary Ltd high fibre ingredients, calcium carbonate. Magnesium carbonate, probiotic, prebiotic Antacid Pellet 400g Gastro Ardmore Equine phytochemicals, mucosal agents,, natural antibiotics, natural stress reducers Other Paste 1 syringe Ulseraze NAF Powder, lactoferrin, ginger, marshmallow, Liquorice,psyllium seeds, phosphotidylcholine, Other Powder 60g U-Guard Equine America Calcium carbonate, kaolin, liquorice, aloe Vera, iron oxide, dried apple pectin pulp, magnesium silicate, vitamin B5 and magnesium oxide. Antacid Coats & protects Powder 40g Stomacare Twydil polyunsaturated fatty acids, phospholipds, chitosan glucosamine fibre Antacid Coats & protects Syringe 1-2 syringes (60-120g) Dietary prevention of ulceration Mark Tompkins chairman of the Newmarket Trainers Federations takes the view that “a common sense approach to gastric ulcers is what's needed, with care being taken over the feeding regime and any stress on horses being kept to a minimum”. In essence he is absolutely correct and as we largely know what the dietary trigger factors are, this should be a fairly straightforward process.

Firstly, whilst the need to minimise gut fill from forage is appreciated, we should try to maximise forage intake whenever possible. This serves two purposes by increasing the amount of protective saliva produced, but also reducing the amount of time that horses in training spend without access to feed. Racehorses could benefit from the best of both worlds, if they were fed more hay or haylage for the majority of the time, with the level being reduced to a minimum (1% of bodyweight for hay and 1.25% of bodyweight for haylage) in the 2-3 days before racing. Additionally, any horses that suffer from recurrent ulcers would certainly benefit from turnout onto pasture for some part of the day. Ensuring meal size is minimised can mollify the negative effects of a high cereal intake. Greater number of small meals, rather than a few large ones is the better option.

It is usually the second and third meals of the day that often need to be reduced and be redistributed to a fourth late feed. Addition of generous double handful of alfalfa chaff to concentrate feeds will also encourage chewing and improve saliva production. Supplements fed to help maintain gastric mucosal health are unlikely to be as effective as drug treatments such as Omeprazole. However, they can be used as an adjunct to veterinary therapy following an initial course of treatment, or during periods where drug treatment has to be withdrawn to avoid contravening doping regulations. In choosing a product however, selecting those from companies that have tested the efficacy of their product in a scientific environment is a wise strategy.

Digestion Development - how modern feeding practices affect the natural digestive system

Previous articles in Trainer have looked at how the horse, regardless of what he has been developed to do, remains the nomadic, trickle feeding animal that nature designed him to be. We have also examined how modern diet and management, combined with the physical and mental stress imposed on the competition and racing animal are contributory factors in a variety of problems, including ‘stereotypy’ behaviour such as cribbing and windsucking, and the perennial problem of ulcers and colic.

We know that the horse is essentially a grazing animal, with a digestive tract designed specifically for long periods of foraging, which can be as much as 20 hours per day. Their stomachs seem surprisingly small to some people, in relation to their overall size and the stomach is designed to empty when only two thirds full. Horses cannot vomit so this mechanism is a vital safety function designed to prevent a lethal stomach rupture. Feed then travels from the stomach along the small intestine, an amazing 70-foot-long organ where most starch, sugar, fat, vitamins, minerals and some of the protein is digested and absorbed into the bloodstream. The residual nutrients and fibres then travel to the hindgut, a large fermentation chamber of up to 30 gallons of fibrous material, with literally millions of bacteria and organisms working to digest it. Volatile fatty acids produced by fibre-digesting bacteria provide as much as 70% of energy for horses on a forage diet. Some of the residual minerals, including phosperous, protein and water are absorbed from the large intestine and recycled in the body. B-vitamins are also produced by bacteria in a healthy horse’s hindgut. It is easy to see how efficient the system is for a forage-fed horse and how we begin to compromise that efficiency with modern diet. So where does it go wrong? Grains are much higher in starch compared to hay and grass, which the digestive tract is designed to process. Excess starch is not broken down by enzymes at the start of the process due to a number of factors, a lack of enzymes, starch that is too compact to be broken down or there is insufficient time as the feed goes from the mouth, foregut and hindgut in less than six hours. Lactic acid is produced in the hindgut by starch-digesting bacteria and reduces the hindgut pH, with the result that many entirely beneficial, fibre-digesting bacteria, unable to tolerate the increased acidity, die and release toxins into the hindgut. These toxins often results in colic and related problems. Thus we know that starch in the hindgut is a problem and reducing grain reduces the risk of problems, but what of the competition animal? Exciting and pertinent research by Dr Derek Cuddeford, lecturer at the Royal School of Veterinary Studies, has shown that a new form of pure, protected yeast can significantly improve fibre digestibility in the horse, resulting in increased energy available to the animal.

This activity has only been demonstrated with a limited number of yeast strains; an example of which is Biosaf Sc47 produced by Lesaffre Feed additives in France. Dr Cuddeford says that Biosaf Sc47 has been used to good effect in starch-rich diets for high performance cattle and other ruminants for some time. “As soon as the yeast is swallowed it goes straight into the site of fermentation in the rumen where it has been shown to stimulate the growth of fibre-digesting organisms by mopping up oxygen and rapidly fermentable material (such as starch) as well as stimulating the numbers of organisms that use up lactic acid in the gut. “Obviously, this would be great if the same could happen during fermentation in the horse’s large intestine due to the risk of acidosis (excess lactic acid) in horses fed large amounts of starch. It seems that yeast must be actively metabolising and thus alive, to fulfil some of its most important functions. This can be a problem in the horse where the site of activity is in the large intestine and thus, yeast has to survive passage through the highly acid stomach in order to reach the caecum and be viable.”

The producers of Biosaf SC47 use a special process whereby live yeast cells are coated with dried, dead yeast cells that act as a protective barrier to the live yeast inside, likened to a Malteser sweet, which more mature readers will recall was advertised as ‘melt in the mouth and not in the hand’! In contrast, ordinary ‘instant yeasts’, such as Baker’s yeast, are highly vulnerable to attack by enzymes, liquids, acids, etc. Research carried out at The Royal School of Veterinary Studies, University of Edinburgh set out to test whether Biosaf Sc47 would survive passage through the horse’s stomach and small intestine. Firstly, some laboratory tests were set up to determine the resistance of this yeast preparation to exposure to acid and the enzyme pepsin normally produced in the stomach. Dr Cuddeford says they were able to show that the Biosaf Sc47 survived prolonged exposure to this strong acid/enzyme combination and it was estimated that one third of an oral dose would survive passage through the horse’s gut to reach the site of fermentation and to be active. “Some further studies were undertaken to test survival through the whole of the horses gut simply by feeding horses Biosaf Sc47 and collecting the droppings and analysing them for the presence of the yeast. Active yeast was recovered from the faeces confirming that this ‘protected’ yeast survived in the horse’s gut and was thus able to benefit the horse. However, it is important to remember that yeast cannot colonise the horse’s gut and thus must be fed on a daily basis. “Live yeast in the large intestine of the horse will utilise any free sugars, scavenge oxygen, stimulate both the growth of lactate-utilising organisms and those bacteria that ferment plant cell wall.

The overall effect is to enhance the digestive process in the horse’s large intestine and to reduce the risk of sub-clinical disease (acidosis) in those animals fed infrequent large meals. Apart from the role of Biosaf Sc47 yeast in stabilising the horse’s hind gut, yeast cell wall contains complex sugars known as mannan- oligosaccharides (MOS) that bind to pathogens thereby preventing their attachment to the gut wall, and thus preventing them from interfering with absorption of nutrients etc. “Thus, certain strains of yeast, together with yeast cell wall, can fulfil very important functions within the horse and this activity has been verified by quite a large number of experiments.” This is an exciting development in equine nutrition with significant implications for the high-performance horse. UK equine supplement and balancer manufacturer TopSpec includes Biosaf SC47 in its Bloodstock and Racing balancers.