How the digestion of nutrients may improve horses’ overall condition

By John Hunter

The importance of breeding and training are well established, but there are many differences in the way yards prepare their horses. For several years our group—a trainer, a vet, and a physician specialising in nutrition and the gut—have been working to see if we could improve equine health and performance using a scientific approach.

The aim has been to explore ways in which the biochemistry underlying the digestion of nutrients might improve horses’ overall condition. In some cases this involved applying developments in the field of human nutrition to horses.  In others we have tackled well-established problems within equine physiology. 

Beetroot juice supplementation

Beetroot is a rich source of nitrate and is frequently taken by athletes to improve their performance. Nitrate produces nitric oxide, which dilates blood vessels, thus reducing blood pressure, increasing blood supply and promoting glucose absorption, and potentially increasing the energy available for high-speed exertion. However, not all athletes appear to benefit, and there had been no study so far on the effect of beetroot juice in horses.  

Twenty racehorses (colts and geldings) in full training were divided into two groups. All were fed their standard diets. One group received beetroot juice with a sweetener to mask the taste and the other a sweetener only for four weeks. After four weeks, nitrate levels in the blood were measured and compared to the starting levels. The level of nitrate rose very slightly in the test group, but no change in performance or condition was noted in any of the horses. Beetroot juice does not seem to help horses.

Vitamin B12

Vitamin B12 is important, not only for preventing anaemia and maintaining the health of the nervous system, but also because it produces enzymes which are crucial for allowing the entry of nutrients into the biochemical cycles producing the main source of energy in both man and horse: ATP. In humans, B12 is derived from eating meat, fish and dairy products. Horses and other herbivores, obtain their vitamin B12 by ingestion of cobalt from pasture which is then used by intestinal microorganisms to form the vitamin. As racehorses are rarely turned out on pasture, most feed concentrates are supplemented with B12.

‘As the intensity of work increases, the composition of the diet and the amount of food consumed change as a consequence of the increased consumption of starchy cereal grains. This will alter not only the dietary supply of B vitamins but also the intestinal synthesis…and it is an open question whether the rate of their absorption is exceeded by tissue demand when horses are in intensive training’ (Frape 2010, p250).

The amount of soluble carbohydrate in the diet of the racehorse must be carefully regulated. ‘Racehorses on a high-concentrate/low-roughage diet and little access to grazing are to some degree already on a metabolic knife-edge’ (Ramzan, 2014, p258).

The trainer was concerned that a number of horses in his yard were below par from the start of the Flat season as their appearance and performance were disappointing. Their diet was unchanged, but they ate poorly and failed to regain weight after racing. Veterinary investigations, including full blood screening, failed to reveal any cause.

As lethargy and early fatigue are two of the earliest symptoms of B12 deficiency in man, it was decided also to check the B12 status of the horses affected. Twenty racehorses, which were out of condition, were identified and divided into two groups. Blood samples were taken, and B12 levels were recorded.  One group was supplemented with B12 injections at 3mg twice weekly for three weeks (18mg in total). The other group acted as controls. At the end of that time, the horses’ condition was reassessed by the trainer on his return from a week’s absence.

The concentration of vitamin B12 in the 20 horses was found to lie within the normal range and was slightly greater than that found in healthy yearlings on pasture at a local stud. After B12 injections, the level rose significantly. A further determination later in the season showed that this initial increase had disappeared. Overall there was no difference between the blood levels of B12 at the end of season compared to the beginning. Changes in B12 concentration, however, did not affect performance. The trainer, who was not informed which horses had received B12 supplements, considered that 8 horses had improved and 12 had not. These were equally distributed between the two treatment groups, and those considered to have improved did not have higher levels of B12.

Thus, despite previous anxieties, racehorses on standard diets have normal B12 levels which remain satisfactory throughout the season. Supplementary injections increase blood concentrations temporarily, but there was no correlation between blood B12 concentration and performance.

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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)

The importance of worming - keeping parasites under control

The use of homespun and herbal remedies may have been superseded by wormers formulated after lengthy research programmes, but the control of worms in the horse remains as important for horsemen today as it was when the significance of these unwanted passengers was first understood.

The main internal parasites of the horse are small red worms (Cyathstomins), large red worms (Strongyles), round worms and tapeworms. The worms undergo similar lifecycles: Larvae and eggs are ingested by a grazing horse and they mature within the gastrointestinal tract. The adults pass out eggs and immature stages in the dung which reinfect the pasture, allowing the cycle to be completed. Infestations with Bot Fly larvae may also be seen.
The development of all these parasites within the equine gut has the potential to cause clinical problems, including colic and ill thrift. However, the lifecycle of the cyathastomins can be particularly destructive.  Cyathostomin larvae actually grow and develop within the wall of the horse’s intestine, causing disruption to the highly specialised intestinal cells. In addition, the larvae have the ability to arrest their own development, entering an encysted or hibernatory phase within the gut wall. Importantly, during this encysted phase the larvae are relatively impervious to a number of common antheImintics (wormers) and over time the parasite burden on the horse may accumulate, with large numbers of larvae entering the encysted phase.
Following the encysted phase, the larvae continue their development by growing and literally bursting out through the gut wall to mature into adults within the lumen of the gastrointestinal tract. However, a cruel twist to the cyathastomin lifecycle is that thousands of encysted worms appear to coordinate their emergence from hibernation, usually in the spring. Large numbers of larvae emerging at once can give rise to a variety of clinical signs from slight lethargy, anaemia and weight loss through to spasmodic or obstructive colic.  Large areas of damaged gut may be replaced by scar tissue instead of the specialised, absorptive cells of the intestine, potentially resulting in weight loss and diarrhoea. Our equine athletes must be able to utilise the high quality (and expensive!) feeds we offer them, and this necessitates a healthy gastrointestinal tract. Thankfully, it is unusual to hear of parasite-associated mortality in racehorses but it would be interesting to know the contribution  made by infestations to sub-optimal performance or training days lost.
It has been accepted for many years that the routine worming of horses is important for their health. This is especially true in establishments with a young and constantly changing population of horses, or pastures which are heavily stocked or grazed by multiple horses. Although all of these conditions are likely to prevail in racing yards, parasite-associated problems could formerly have been dismissed as irrelevant to the well-organised yard with a sound worming policy. Unfortunately, things are now not so simple and it appears that the worms are fighting back. Keen to ensure the survival of their own  kind, they are evolving new strains that are resistant to some anthelmintics. It is not scaremongering to say that some horsemen may soon have no effective means for controlling the internal parasites affecting their charges.
Resistance can occur when any chemical is regularly used to control an infective organism, hence the problem of bacteria resistant to several types of antibiotic found in hospitals e.g. MRSA. In some cases ‘operator error’ may be to blame for encouraging the development of resistance. Incorrect dosing (particularly under-dosing) with anthelmintics may promote the evolution of resistant worms.
Only three classes of anthelmintic are licensed for use in the horse and red worms resistant to the benzimidazole group are common in thoroughbreds. Pyrantel forms the second class. Strongyles resistant to pyrantel developed in the USA where it was used as a feed additive. They are increasingly recognised as a problem in Europe. More worryingly, resistance is developing to the third and final class of wormer, the macrocyclic lactones (ivermectin/moxidectin). Round worm control in foals is not guaranteed by their use and cyathostomins resistant to them are now present on a donkey sanctuary in the UK. Evidence for  cyathstomin resistance has also emerged from Brazil and Germany. It may be the case that resistance has not been detected in more countries due to lack of testing, rather than no resistant parasites being present.
Clearly, planning the worming regime is of the utmost importance and requires detailed knowledge of the strengths and weaknesses of different worming products. However, in a telephone survey of English racehorse trainers in 2002, only 42% stated that their choice of anthelmintic was based on veterinary advice. Furthermore, the same study suggested that strategies used for the treatment of new arrivals were unlikely to prevent the introduction of resistant worms or the development of encysted red worms in the majority of cases.
It is also known that the parasite burden of horses in a yard is not distributed evenly. Most horses will be relatively worm-free. However, one or two ‘wormy’ individuals will be contributing the majority of eggs to the pasture. Identifying these individuals is done by performing faecal worm egg counts (FECs) regularly on all horses within the yard. This could also facilitate a change in the way wormers are used on training yards, moving away from pre-planned blanket dosing of the whole yard to treating only those individuals which require it. Current thinking would suggest that only horses with FECs in excess of 200 eggs per gram (epg) should be treated. An important point to make regarding FECs is that they do not detect encysted/immature red worms.
It is also possible to establish the resistance status of the worms in the horses on the yard. FECs are performed at the time of treatment and repeated afterwards to ensure that the wormers have worked, the faecal egg counts have been reduced and that the horses don’t harbour resistant populations of worms. In the case of pyrantel, the FEC should be repeated seven days later and resistance should be suspected if the FEC is reduced by less than 90%. For benzimidazoles, the count is taken 14 days later and the FEC should be reduced by over 95%. The interval for ivermectin is 21 days and FECs should be less than 1% of the previous level if resistance is not to be suspected. The persistence of Moxidectin makes it unsuitable for this type of test.
Tapeworms have been implicated as a factor in cases of colic. Work at Liverpool University has lead to the development of a test for the presence of tapeworm which can be performed on a blood sample. This indicates if treatment is necessary and can be repeated to check that anthelmintic treatment has been successful.
Although this monitoring may appear to be time-consuming, it would allow a very accurate picture of control programme efficacy to be established. The use of expensive anthelmintics is curtailed and selection pressure for resistance on the parasites is reduced.
As previously mentioned, a protocol for new horses on the yard is extremely important. Recent arrivals should be confined to their box, or allowed access only to a quarantine paddock. An FEC should be performed. It is best to assume that the animal is carrying encysted red worm larvae and to treat for these with moxidectin or five daily doses of fenbendazole. If later FECs suggest the presence of resistant worms, the horse should be assigned its own paddock, or returned to where it came from.
When worming any horse, it is important to follow some basic guidelines to ensure the correct dose is administered. Anthelmintics, or any other drugs, should only ever be given by the route prescribed on the data sheet. An accurate weight should be obtained for each horse to be treated and the full dose for that weight given. If there is any doubt about the accuracy of the weight i.e. obtained by measuring tape, then it is best to slightly overestimate the dose. Ensure that each horse ingests their full dose of paste by holding the head up until it is swallowed. Giving inadequate doses of wormer may hasten the selection of resistant parasites. Animals identified as requiring an anthelmintic treatment which share grazing should receive synchronised treatments. This will help to prevent an immediate major reinfection. It is now advised that, where more than one class of wormer is still effective, they should only be rotated on an annual basis.
Worm control is not all about the use of anthelmintics and these alternative strategies assume an even greater importance with the advance of resistant parasites. They mainly involve reducing the level of contamination on the pasture and so preventing the worms from completing their lifecycle in the gut of the horse. The most direct method is to remove faeces from the grazing, ideally twice weekly during the summer and once per week over the winter. This can be done manually or by machine.  Sheep and cattle will ingest the equine parasites, but are not themselves affected and so clean the grass for horses. Simply lowering the stocking density on the pasture will also help.
Thoroughbred breeders may also have a role to play in worm control. Faecal egg counts may not be the first thing that comes to mind when planning matings, but that may have to change. Resistance is developing to our third and final class of anthelmintic and no new wormers licensed for equines are likely to be on the market in the near future. We know the debilitating effects of an untreated, or possibly untreatable, worm infestation. A horse carrying a heavy infection would never be able to realise its full potential. So, without a major re-evaluation of anthelmintic use, it may be that the classic winners of tomorrow are descended from the innately parasite-resistant individuals of today.  

Dr Philip K Dyson BVMS Cert. EM and Barry Sangster BVMS MRCVS
 (19 May 2007)

Time for a re-think? Why do we deny a horse water and fibre before a race?

Removal of fibre and water intake before a race are supposed to enhance performance in Race Horses… Surely this is not sound practice, let alone science. No sensible, modern day athlete would go out of their way to cause discomfort in their digestive system and thereby reduce performance, let alone remove hydration. Perhaps the racing industry should look outside their field of view and take a leaf out of the endurance horse world. In this field of horsemanship, horses are fed just before and even during competition and hydration of the horse is paramount. Common sense says that a happy and comfortable horse will give us its ‘all’. Perhaps now is the time for a bold trainer to take this on board. The following is a more scientific rational behind my thinking.

The evolution of the horse into the animal we know today has meant the development of a very specialised digestive system. The proportionally huge hind-gut indicates the importance of fibre/forage in the equine diet. The specialised stomach has evolved to cope with a nearly continuous intake of fibrous plant material, so that (unlike the stomachs of omnivorous and carnivorous animals) the pyloric sphincter allows a ‘trickle’ of partly digested material into the small intestine. This function may cause a problem for horses fed a high level of concentrates as this ‘trickle’ mechanism can allow food to pass through the sphincter, before sufficient digestive processes have taken place. Also the acid level in the equine stomach is relatively high, as it has evolved to start the breakdown of cellulose in plant material, ready for digestion.

It has been suggested that inadequate provision of fibre in the diet may be a reason for many cases of stomach ulcers in horses. For optimum health and performance all horses require a balanced supply of :- Fibre – 1) indigestible fibre – for gut health and motility and 2) digestible fibre for nutrients and energy – the cellulose of plant material is broken down by colonies of microbes in the hind-gut into ‘complex’ carbohydrates, producing Volatile Fatty Acids which are absorbed into the blood stream, transported to the liver and converted into fat. This fat can be utilised by the body cells for energy or stored as adipose tissue until further energy is required. The process of fermentation and absorption of volatile fatty acids continues for many hours, so that horses may draw on the stored energy as required.

Good quality hay and pasture can provide much of the essential nourishment required for general maintenance and health, always providing that a balanced supply of micronutrients is fed. For horses in strenuous work, high energy fibre sources such as alfalfa chaff and sugar beet shreds can be a valuable part of the ‘short’ feed. The provision of adequate dietary fibre, in the daily diet, satisfies the equine ‘trickle’ feeding system and also the physiological and psychological need to chew.

Starch & Sugars – ‘simple’ carbohydrates for an energy supply – from oats and micronised cereals, Care has to be taken with quantities fed, as cereal overloading has been considered as a possible ‘trigger’ for problems such as ‘set-fast’, laminitis, azoturia etc. The choice and balance of cereals in the diet is also important, as some horses have been found to show an apparent intolerance to barley, exhibiting skin eruptions, filled legs and/or excitable ‘mood swings’. Cereals are broken down into their component glucose molecules in the small intestine and absorbed into the blood stream.

This ‘blood sugar’ can be directly utilised by the muscles as a valuable ‘fast release’ energy source for short bursts of strenuous work or stored in the muscles or the liver as glycogen. During prolonged exercise a problem found to be associated with fatigue – hypoglycaemia (low blood sugar) – may be avoided by the provision of sugars such as molasses in the diet. Vegetable Protein – for tissue repair and development of almost all body constituents; Cereals contain a very small percentage of protein which is digested in the small intestine. Soya beans, an excellent source of quality protein, are also digested in the small intestine; providing the 22 amino acids commonly recognised as essential in the horse’s diet. Most importantly the limiting amino acids lysine and methionine, as they are likely to cause metabolic problems if in short supply. Methionine is classified as an essential amino acid, it helps lower cholesterol levels, reduces liver fat protects the kidneys and regulates ammonia formation, also a natural chelating agent for heavy metals.

Certain amino acids are necessary for the metabolism and utilisation of energy. It is recommended that care should be taken to supply a correct balance of protein for horses under six years of age, as they are still in the growth and body building stage and will have greater requirements for protein and the associated, necessary micronutrients than the mature horse. Lysine is the amino acid involved with growth as are the minerals calcium, phosphorus, copper and zinc for the strength and integrity of cartilage and bone. However overly high intakes of protein can lead to an increase of urinary ammonia producing and/or aggravating respiratory problems for the stabled horse. Also, over feeding protein can cause an increase in the requirement for water possibly leading to a certain amount of dehydration and at least very wet beds - with a resulting increase of ammonia! . Fats/Oils – 1) as an energy source, 2 ¼ times the energy of carbohydrates per unit weight. 2) as an insulating layer of subcutaneous fat and 3) for development and maintenance of cell membranes. It is thought that fats may prove valuable in increasing the performance of horses at sustained submaximal exercise by providing a higher energy density diet, with the risks of carbohydrate overloading likely to be reduced.

The horse conditioned to an intake of oil in the diet will be able to accept more demanding training sessions, leading to increased fitness and performance . Made up from ‘chains’ of fatty acids, linoleic, linolenic and arachidonic acids are considered to be important for the horse.

If the blood glucose and muscle and liver glycogen energy stores have been depleted then the body will convert to fat oxidation for metabolic energy. – from ‘ The Scientific Rational for High Fat Diets for Equines’ Deborah M Lucas MSc, CBiol, MIBiol, R.Nutr. Minerals – almost every body process requires a correct supply (the feral horse fulfilled requirements from a variety of herbage grown in different soil types).

Minerals rarely act on their own, but interact in groups and with Vitamins, so that a deficiency or excess of one may affect many body processes; for example, research suggests that excessive iron intake may cause a type of metabolic corrosion affecting both respiratory tissue and working muscle. Also a balanced supply of trace elements such as selenium, copper, zinc and manganese along with vitamins E and C is advisable, to protect cell membranes from ‘free radicles’ and help control ‘oxidative’ stress for horses in heavy exercise, under stress and when travelling etc. Vitamins – as above almost every body process requires a correct supply.

Vitamins rarely act in isolation but interact with other vitamins and with minerals. For optimum health and performance a correct and balanced supply is essential. For example – the normal requirement for Vitamin K (important for the blood clotting mechanism) can be met through microbial digestion in the gut, if quality forage is supplied; but a deficiency has been considered to be a cause of pulmonary bleeding and internal haemorrhage, so it should be supplied in the diet of the stabled, working horse. The important B complex vitamins can also be manufactured by the gut microbes during the digestion of forage, but additional dietary supplementation will be required for stabled horses in work . The correct storage of Vitamins is vital as they are sensitive to heat, light, moulds and oxidising agents.

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.

The role of protein in the racehorse's diet

Dietary protein is probably one of the most talked about elements of a racehorses’ diet, which is unfortunately ill deserved. Whilst the level of protein in the diet is important for tissue growth and repair, it is probably the least important source of energy to the athletic horse when compared to starch, fibre and oil. Protein has received a lot of ‘bad press’ in racing in the past, with both inadequate and excess intake being used to explain poor performance.

Excessive protein in the diet has also been blamed for racehorse excitability and even for conditions such as itchy or bumpy skin (urticaria) and tying up. More recent evidence suggests that protein per se is unlikely to be the major culprit in these situations. However, far from being undesirable, protein is an essential part of a horse's diet, as it provides the building blocks needed for tissue growth and repair and also for the synthesis of many important body chemicals such as enzymes and hormones. These building blocks are known as amino acids and each protein source used in horse feed has a characteristic amino acid makeup or profile. Look for quality and not just quantity Protein is digested primarily in the horse’s small intestine by the action of digestive enzymes; however, a varying proportion of the protein in feed may escape digestion in the small intestine and reach the hindgut, where it is fermented by the resident microflora. Although this latter method of breakdown can be beneficial to the hindgut microflora, the resultant amino acids released are generally not absorbed and so are unavailable for use by the horse. So the horse relies on dietary protein being digested in the small intestine, as far as possible, to provide a useable source of amino acids. Proteins from different sources are digested here to a greater or lesser extent, with the protein from cereals (oats, maize) and oilseeds and pulses (soya, linseed), generally being more digestible in the small intestine than that from forages.

In exception to this, the protein digestibility of alfalfa is relatively high compared to other conserved forages such as hay or haylage. Horses can synthesize some amino acids in the body, whilst others must be supplied in the diet and are known as the essential amino acids. The quality of a protein source is measured by not only its ability to be digested in the small intestine, but also by how much of these essential amino acids, in particular lysine that it provides (see table below). Commonly used protein sources for horses Protein Source Total Protein (%) Lysine (%) Soybean meal 55 3.0 Oats 12 0.5 Alfalfa 15 0.6 Hay 7.0 0.1 Inclusion of a proportion of a very high quality protein source such as soya, either within the existing racehorse mix or cube or as part of a high protein feed used to top-dress the diet is an advantage. How much protein is enough? An average mature horse in full work needs about 1.5 times the amount of protein per day compared to the equivalent requirement for the same horse in light work. Yearlings and two year olds have a slightly higher protein requirement compared to there mature counterparts, in the early stages of training when in light work. However, once their workload has increased, this extra protein requirement is more than covered by the increased requirements for hard work in itself. The bottom line for young horses coming into work is that the feed chosen for this stage of training needs to be considered carefully and ideally, whilst being relatively low in energy should have a slightly higher protein content compared to an ordinary low energy feed.

Many of the ‘recovery’ type products are suitable for this purpose or alternatively addition of a small quantity of a high protein supplement feed can suffice. As far as horses in harder work are concerned, their increased requirement for protein would easily be met by the increase in quantity of feed used in the transition from light training to hard work, irrespective of age. So providing that you are using decent quality hay or haylage and a feed designed for hard work or racing, the issue of inadequate levels of protein in the diet should not arise. It is always worth having batches of hay or haylage analyzed to ensure that amongst other things the protein level is not outrageously low or equally excessively high. In reality, there are probably far more racehorses being overfed protein and underfeeding is only likely to occur when forage is being used that is particularly stemmy and mature and has a related very low protein level. In contrast, excessive protein intake in the diet is likely to be more prevalent and some of the potential consequences are discussed below.

Ammonia and dehydration are two issues with excess protein intake One of the main issues with overdoing protein intake is the effect that it can have on both hydration status and respiratory function. If a horse is fed above and beyond its requirements for protein, the excess amino acids produced from its digestion will be re-processed by the liver and the nitrogen containing part, which is toxic, must then be converted to harmless urea, which is then eliminated in the urine and faeces. However, unfortunately no matter how meticulously clean a racehorse’s bed is kept, bacteria present will soon start to breakdown the urea to produce ammonia, which has a characteristic pungent smell and has consequences for the health of both horses and their lads or lasses respectively. When ammonia combines with water in body tissues it can become extremely irritating and harmful to the eyes, sinuses and respiratory system.

In humans short-term exposure to high levels of ammonia can cause upper and lower respiratory tract irritation and oedema, and over the long-term can contribute to chronic bronchitis and may exacerbate other lung diseases including asthma. In horses, ammonia restricts the movement of cilia (brush-like hairs) in the airways that filter out harmful dust particles, and its corrosive action causes inflammation and a build up of mucous. Independent consultant and respiratory expert Dr David Marlin warns that excessive ammonia inhalation in horses could cause irritation of the respiratory tract and exaccerbate other pre-existing conditions such as is recurrent airway obstruction RAO (formerly known as chronic obstructive pulmonary disease, COPD, heaves) or inflammatory airway disease (IAD).

In addition to the ammonia issue, overfeeding protein can often result in horses drinking more and urinating excessively. This not only leads to wet beds, but can contribute to dehydration in horses. It is widely accepted that dehydration is a major factor in reduced exercise performance for horses involved in fast exercise. Too much or too little? A potential sign of a large surplus of protein in the diet is a horse that is drinking to excess and that has a wet smelly bed. Using blood results to assess protein status is not unfortunately as straight forward as simply looking at the level of plasma total protein. Plasma total protein for a horse in training is likely to fall between 53-67g/l. However, there are many factors, which influence this result in addition to the level of protein in the diet and therefore a high or low plasma total protein is not exclusively indicative of inadequate or excess protein in the diet. A more useful measurement may be the ratio of blood urea nitrogen (BUN) to creatinine, with values under and over the normal range being related to inadequate or excess dietary protein intake, respectively.

Another approach is obviously to have the ration checked by an experienced nutritionist, although, this would obviously require analysis of the forage and feeds, especially where straight feeds are used. Whilst excessive protein intake potentially can have a negative impact on horses in training, quite often the protein content of the diet is maligned without justifiable cause as discussed below. Is a high protein diet implicated in tying up? An excess protein intake was historically blamed for episodes of Azoturia or ‘tying up’ in racehorses. This is largely unfounded, as although the exact triggers for tying up are not fully understood, there are a number of other dietary related factors, which exclude protein, that have been implicated in its occurrence.

Tying up is more commonly associated with high-energy diets, where a large part of that energy is supplied in the form of hydrolysable carbohydrates (starch and sugars). In addition macro and micro mineral availability and balance (calcium, phosphorus, magnesium and selenium), electrolyte supply (sodium, potassium and chloride) and antioxidant provision (vitamin E), as well as other factors such as stress and excitable behaviour are more likely to be relevant. Hives, protein bumps, urticaria – too much protein?

Once again, the general consensus in racing is that the skin disorders often describes as hives, protein bumps or urticaria are simply due to too much protein being fed. However, veterinary research would counter this, as leading dermatologists suggest that feed allergies, although they can occur, are much more rare than is commonly accepted. Certainly, where feed is implicated in the development of these skin disorders it is much more likely to be due to a sensitivity to a particular source of protein such as barley or wheat, rather than simply a general excess. Before feed is implicated, however, other more likely causative factors such as cereal or forage mites, washing powder, fungal skin or other general infections should also be discounted.

Where sensitivity to a particular protein source is seriously suspected, an exclusion diet can be used to identify the source of the problem. This involves feeding forage only for a period of time until the bumps have disappeared and then slowly re-introducing elements of the concentrate feed in an attempt to isolate the culprit. Much of the confusion surrounding protein in my opinion is due to the relationship between the energy content of a feed (DE MJ/kg) and the protein content (%). In general terms, as you move upwards through the portfolio of feed ingredients and compound feeds, as energy content per kilogram increases, so does the protein content of the feed in percentage terms. This is not because protein is a major energy source, but simply because the higher energy ingredients tend to have a higher protein content naturally. This causes much confusion and as more and more feed companies now declare the energy content of their feeds on their packaging or in their literature, there needs to be a move towards choosing feed by energy level and not percentage protein.

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.