Why are gastric ulcers still a significant concern for horses in training?

By Catherine Rudenko

With the advances in scoping and increased awareness of gastric ulcers, along with the high prevalence found in horses in training, one may wonder, Why is this condition still such a problem? Do we not know enough to prevent this condition from recurring?

The short answer is that much is known, and for certain, there are effective medications and many feeds and supplements designed to manage the condition. The underlying problem is that the factors leading to ulceration, at least the most significant ones, are fundamental to the routine and management of a horse in training. Quite simply, the environment and exercise required are conducive to development of ulcers. Horses in training will always be at risk from this condition, and it is important to manage our expectation of how much influence we can have on ulcers developing, and our ability to prevent recurrence.

Clarifying Gastric Ulceration

Before considering how and why ulcers are a recurrent problem, it is helpful to understand the different types of gastric ulceration as the term most commonly used, Equine Gastric Ulcer Syndrome (EGUS), is an umbrella term which represents two distinct conditions.

The term EGUS came into use in 1999 and represented ulceration of the two separate locations in the stomach where ulcers are found: the squamous and glandular regions. The two regions are functionally different, and ulceration in either location has different causative factors. This is important when considering what can be managed from a risk point of view at a racing yard. The term EGUS is now split into two categories: Equine Squamous Gastric Disease (ESGD) and Equine Glandular Gastric Disease (EGGD).

ESGD is the most commonly occurring form and the focus of dietary and management interventions. The majority of horses in training have the primary form of ESGD where the stomach functions normally. There is a secondary form that relates to a physical abnormality which causes delayed emptying of the stomach.

The condition ESGD is influenced by the training environment and time spent in training as noted by researchers looking at prevalence of horses out of training compared to those within training. In this case, 37% of untrained thoroughbred racehorses had ESGD and this progressed to 80-100% of horses within two to three months of training. This effect is not unique to thoroughbreds and is seen in other breeds with an ‘active workload’; for example, standardbreds progress from an average of 44% ESGD in the population to 87% when in training. Such research is helpful in understanding two things: firstly, that ulcers in the squamous section can occur outside of training, and that the influence of exercise and dietary changes have a significant effect regardless of breed. Even horses in the leisure category, which are thought of as low risk or at almost no risk at all, can return surprising results in terms of prevalence.

Risk Factors

There are multiple risk factors associated with development of ESGD, some of which are better evidenced than others, and some of which are more influential. These include:

• Pasture turnout

• Having a diet high in fibre/provision of ‘free choice’ fibre

• Choice of alfalfa over other forages

• Provision of straw as the only forage source

• Restricted access to water

• Exceeding 2g of starch per kilogram of body weight

• Greater than 6 hours between meals (forage/feed)

• Frequency and intensity of exercise

• Duration of time spent in a stabled environment combined with exercise

Of these factors, the stabled environment—which influences feeding behaviour—and exercise are the most significant factors. The influence of diet in the unexercised horse can be significant, however once removed from pasture, and a training program is entered into, ulceration will occur as these factors are more dominant. An Australian study of horses in training noted the effect of time spent in training, with an increase in risk factor of 1.7 fold for every week spent in training.

Once in training, there is some debate as to whether provision of pasture, either alone or in company, has a significant effect. …

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Nutrition - antioxidants - their role in racing - is there merit in specifically supplementing antioxidants to enhance performance?

By Catherine Rudenko

Antioxidants are substances that slow down damage to organisms created by the presence of oxygen. The need for antioxidants is always there, in all species, increasing as exercise intensity and duration increase. Is there merit in specifically supplementing antioxidants to enhance performance?

The nature of antioxidants

There are many forms of antioxidants naturally present within the body and supplied through the diet. One key feature of antioxidants is that they are ‘team players’. No one antioxidant alone can maintain the system, and some will only function in the presence of another antioxidant.

The role of an antioxidant is to keep reactive oxygen species (ROS) or free-radicals created in the presence of oxygen at an optimum level. Oxygen is required for life, it is always present, but as an element, it is highly reactive and so can also have an adverse effect on the body. The reactivity of oxygen in the body produces ROS which cause damage to cellular components such as DNA, proteins and lipids of cell membranes. Some ROS also have useful cellular functions, and so the purpose of antioxidants is not to eliminate ROS altogether but to maintain a healthy balance. In general, antioxidants operate in two ways: either preventing the formation of an ROS or removing it before it can cause damage to a cell component.

Sources of antioxidants

There are multiple sources of antioxidants including vitamins, enzymes and nutrient derivatives. Other nutrients such as minerals, whilst not having antioxidant properties, are also involved as their presence is required for the functioning of antioxidant enzymes. Two key examples are zinc and selenium.

As with many body systems, the ideal healthy balance can often go awry. When the level of ROS present overwhelms the capacity of antioxidants present, the body experiences oxidative stress. There are three main reasons for a horse in training experiencing oxidative stress:

• Increased exposure to oxidants from the environment

• An imbalance or shortage in supply of antioxidants

• Increased production of ROS within the body from increased oxygen metabolism during exercise

Oxidative stress is of concern as it can exaggerate inflammatory response and may be detrimental to the normal healing of affected tissues. Oxidative stress during strenuous exercise, such as galloping or endurance, is typically associated with muscle membrane leakage and microtrauma to the muscle. Oxidative stress is now understood to play a role in previously unexplained poor performance.

Dietary antioxidants photo: horse eating?

Given the demands of training and the regularity of intense exercise and racing itself, the use of dietary antioxidants is an important consideration. As antioxidants are generally best considered as a cocktail, it is necessary to give consideration to provision of nutrients and their derivatives across the total daily diet.

The majority of racing feeds will be formulated to provide a good cocktail of basic antioxidants or their supporting minerals. All feeds will contain vitamin E, selenium and zinc for example. Some, but not all, feeds will also provide vitamin C. The source of these nutrients may also differ; for example, some feeds will contain chelated zinc or organic selenium, which offer improved availability. The source of vitamin E will also vary—the majority being provided as synthetic vitamin E; but some will include natural sources of vitamin E, which is more effective.

TOP: Oxidative stress is now understood to play a role in previously unexplained poor performance.

Once a good base diet is in place, consideration for strategic use of individual antioxidants may then be warranted to further enhance the capacity of the body to mitigate the effects of ROS on the muscle. Three popular and commonly used antioxidants are vitamin E, vitamin C and more recently coenzyme Q10.

Vitamin E

As a lipid-soluble antioxidant, vitamin E provides defence against ROS in cells, playing an important role in maintaining integrity of cell membranes. Vitamin E is the most commonly supplemented antioxidant. There are established recommended daily intakes for vitamin E, typically 1000 IU per day for a horse in training; however, further supplementation beyond the basic nutritional requirement can yield benefits. Modern race horse feeds are well fortified—the majority providing upwards of 300 IU/kg, resulting in an average daily intake of over 2000 IU/day.

Intakes of above the base rate have been investigated for their effect on CK (creatine kinase) and AST (aspartate aminotransferase)—two markers of muscle damage. One such study used endurance horses whereby intakes ranged from 1150 IU up to 4750 IU per day. Elevated intakes of vitamin E correlated with lower levels of CK and AST suggest that vitamin E can affect muscle membrane permeability and injury to muscle during exercise.

As a guide to improving antioxidant capacity, an intake of up to 5000 IU per day would be appropriate for a horse in training. Vitamin E intake is influenced by the level of fats fed in the diet; and where additional oils are added, further vitamin intake E is required, as vitamin E will be utilised in stabilising the oil itself. Fats fed in a dry format, such as extruded rice bran, are normally fortified with vitamin E for this reason and do not require further supplementation.

Vitamin E is available in feeds and supplements in two forms: synthetic or natural. The natural form, d-alpha-tocopherol, is made up of a single isomer (chemical unit). The synthetic form, dl-alpha-tocopherol, is made up of eight different isomers—only one of which is molecularly the equivalent of natural vitamin E. The dose rate required to increase serum vitamin E levels in horses is lower for natural E than synthetic vitamin E.

The increased bioavailability of natural vitamin E has led to further research in comparing this source against synthetic vitamin E for efficacy against oxidative stress and physical gait changes. The study used 3 diets: a control diet with the standard recommended intake of 1000 IU/day provided by synthetic vitamin E; a higher intake synthetic vitamin E diet of 4000 IU/day; and a high intake of natural vitamin E at 4000 IU/day. The study lasted for six weeks and measured serum levels of vitamin E at various time points along with markers of oxidative stress, CK and AST levels, and gait analysis.

The key findings:

All diets increased serum vitamin E over time; however, the increase was not significant in the diet, providing only 1000 IU/day of synthetic vitamin E. The greatest difference in serum vitamin E was seen in the natural vitamin E diet where levels increased by 77.25% from day one to the last time point.

Oxidative stress was measured through multiple tests including oxidation of lipids (TBARS). Horses supplemented with natural E had lower levels of lipid oxidation markers than both synthetically supplemented horses at the second exercise test, which occurred after six weeks of fitness training.

AST levels were lower within the two hours post exercise of natural E supplemented horses compared to synthetic vitamin E horses; however, by 24 hours, the difference was no longer significant. There was no noted significant effect on CK.

Gait analysis before and after exercise showed better movement of horses that were supplemented with natural vitamin E. These horses experienced less of a reduction in their stride duration post exercise, potentially indicating less muscle soreness due to less oxidative stress.

As vitamin E is well proven to be an effective antioxidant, it may be tempting to think that ‘more is better’; however, as with all nutrients, there is a safety limit to consider. Current research indicates that supplementing at 10 times the base level—an intake of 10,000 IU/day—may result in poor bone mineralisation and impair beta-carotene (vitamin A) absorption. An intake of 4000-5000 IU/day based on the research above and other studies would appear effective whilst also being well below the presumed safety limit.

Vitamin C

Ordinarily horses can manufacture adequate vitamin C within the body, unlike humans that require direct supplementation. Additional vitamin C is required and often recommended when the body is challenged through disease or periods of stress. …

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Can nutrition influence EIPH? -Catherine Rudenko investigates alternative and supportive therapies as trainers seek to find other means of reducing the risk or severity of EIPH

By Catherine Rudenko

EIPH (exercise-induced pulmonary haemorrhage) was first identified in racehorses in the 16th century. Since this time, the focus has been on mitigating the haemorrhage. Management of EIPH largely revolves around the use of furosemide, dependent of jurisdiction, may or may not be used on the day of racing. Alternative and supportive therapies are becoming increasingly popular as trainers seek to find other means of reducing the risk or severity of EIPH.

Nutrition and plant-based approaches are part of an alternative management program. Whilst research is somewhat limited, the studies available are promising, and no doubt more work will be done as using furosemide becomes more restricted. There are several directions in which nutrition can influence risk for EIPH, including inflammatory response, blood coagulation, cell membrane structure, hypotension and reducing known lung irritants.

Exercise- induced injury may exacerbate the severity of EIPH as a result of the delayed sealing of damaged micro vessels.

The various approaches are all supportive, working on altering an element of risk associated with the condition. Some are more direct than others, focusing on the effect on red blood cells, whilst others work on some of the broader lung health issues such as reducing mucus or environmental irritants. 

None are competitive with each other, and there may be an advantage to a ‘cocktail’ approach where more than one mode of action is employed. This is a common practice with herbal-based supplements where the interactive effects between herbs are known to improve efficacy. 

Cell membrane

The red blood cell membrane—the semipermeable layer surrounding the cell—is made up of lipids and proteins. The makeup of this membrane, particularly the lipid fraction, appears to be modifiable in response to dietary fatty acids. Researchers feeding 50mls of fish oil found a significant increase in the percentage of omega-3’s in the cell membrane.

Essential fatty acids (EFA’s), omega 3 and omega 6, are important cell membrane components and determine cellular membrane fluidity. Fluidity of a cell membrane is important, particularly when pressure increases, as a cell membrane lacking in fluidity is more likely to break. A cell that can deform, effectively changing rather than breaking, has an advantage and is linked with improved exercise performance in human studies. Inclusion of fish oil in the diet increases the ability of red blood cells to deform.

Kansas State University investigated the effect of omega supplementation on 10 thoroughbreds over a five-month period. The diet was supplemented with either EPA and DHA combined, or DHA on its own. EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are specific forms of omega-3 fatty acids commonly found in oily fish. When supplementing the diet with both EPA and DHA, a reduction in EIPH was seen at 83 days and again at 145 days. Feeding DHA on its own did not produce an effect.

Fish oil contains both EPA and DHA and is readily available, although the smell can be off-putting to both horse and human. There are flavoured fish oils specifically designed for use in horses that overcome the aroma challenge and have good palatability. 

Inflammatory response and oxidative stress

Airway inflammation and the management of this inflammatory process is believed to be another pathway in which EIPH can be reduced. Omega-3 fatty acids are well evidenced for their effect in regulation of inflammation, and this mode of action along with effect on cell membrane fluidity is likely part of the positive result found by Kansas State University. 

Kentucky Equine Research has investigated the effect of a specific fish oil on inflammatory response with horses in training. The study supplemented test horses with 60mls per day and found a significant effect on level of inflammation and GGT (serum gamma-glutamyl transferase). GGT is an enzyme that breaks down glutathione, an important antioxidant. As GGT rises, less glutathione is available to neutralise damaging free radicals, creating an environment for oxidative stress.

Kentucky Equine research results

A horse’s red blood cells are more susceptible to oxidative stress than humans, and maintaining a healthy antioxidant status is important for function and maintenance of cell integrity.

Rosehip

Supplements for bleeders will often contain relatively high doses of antioxidants such as vitamin C and vitamin E to support antioxidant status in the horse and reduce risk of damage to cell membranes. Vitamin C has also been shown to benefit horses with recurrent airway obstruction and increase antibody response. Dose rates required for an effect range from 15-20g per day. If including high doses of vitamin C in the diet, it is important to note that any sudden withdrawal can have negative effects. Gradual withdrawal is needed to allow the body’s own mechanisms for vitamin C production to recognise and respond to the change in status.

Rosehips are natural potent antioxidants containing many active substances. Research into the effect of rosehips specifically on red blood cells has shown they have a high efficacy when assessing their ability to ameliorate cell damage.

Hypotensive herbs

Caucus carota – wild carrott

The essential oil of caucus carota species is a well-documented oil having a hypotensive, lowering of blood pressure effect along with antifungal properties. Its antifungal effects are noted against aspergillus species, a common cause of poor respiratory health. Allium sativum is also well known for its ability to lower blood pressure. An initial study (data unpublished) into the effects of these two plants along with herbs reported to alleviate mucus in the lungs has shown promising results in a group of horses in training. 

Prolonged blood coagulation

As prolonged blood coagulation is cited as a possible factor for EIPH, herbal products that are noted for their ability to enhance coagulation are in certain parts of the world widely used as part of managing EIPH. …

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Starch v fibre intake. Balancing different carbohydrate sources against changing requirements of fitness, injury and recovery

By Catherine Rudenko

Carbohydrates are by far the largest component of any horse’s diet, typically two thirds by weight, yet we often focus more on other nutrients, such as protein—which in comparison forms only a small portion of the total diet at around 8-13%. Carbohydrates, specifically the balance between differing carbohydrate sources, influences three key areas relating to performance.

The choice of carbohydrate influences the type of energy available, providing varying proportions of ‘fast release’ or ‘slow release’ energy. The type of carbohydrate chosen also impacts behaviour, increasing or decreasing risk of excitability and certain stereotypical behaviours. Last, but by no means least, the choice of carbohydrate and the way in which it is fed impacts digestive health and the ability of the digestive system to convert food to ‘fuel’ for the body.

Getting the balance right between the different types of carbohydrates is important for getting the right results when having to adjust the intensity of training, when resting a horse and when working back up through the stages of fitness. 

What are carbohydrates? 

There are different ways of classifying or grouping carbohydrates, depending on whether you take things from the plant’s point of view or that of the digestive anatomy of the horse. Working with the horse in mind, carbohydrates are best classified by the section of the digestive system that they are processed in—either the small intestine or large intestine. The site of digestion determines the type of energy provided, often referred to as fast releasing for the small intestine and ‘slow releasing’ for the large intestine. The group of carbohydrates, known as hydrolysable carbohydrates, are the group behind the description of fast releasing, whilst the group known as fermentable carbohydrates are those forming the ‘slow releasing’ category. Within the fermentable group, there are three sub groups of rapid, medium and slow. 

What are carbohydrates made of? 

There are many types of carbohydrates in the horse’s diet, ranging from simple sugars to more complex structures. They are defined by their degree of polymerisation, which refers to the way in which sugar units are joined together. How a carbohydrate is formed and the type of link present are important as they determine if digestion is possible in the small intestine or whether fermentation in the large intestine is required. This influences the type of energy available. 

For horses in training, the type of carbohydrate of particular interest is the polysaccharide group which includes starch, cellulose, hemicellulose and fructans amongst others. Starch is found in significant quantities in hard feeds, whilst cellulose and hemicellulose, amongst other fermentable carbohydrates are abundant in forages. Pasture is a source of fructans, which can change rapidly depending on growing conditions and daylight hours. 

Structure

Single sugars, also called simple sugars, comprise one unit only. They are categorised as monosaccharides—the most commonly known being glucose. For horses in training this is a highly valuable sugar as it is the main ‘fuel’ for muscles. Glucose forms the basis of many of the more complex structures of interest to horses in training.

When two sugars join together, they are known as a disaccharide—the best known being lactose which is found in mare’s milk. Oligosaccharides refer to more complex structures where more units are joined together—a common example being fructo-oligosaccharide (FOS) which many horses in training are specifically fed as a prebiotic to support digestive function. 

Type of Carbohydrate

Polysaccharides, our group of particular interest, are significantly more complex chains that are branched and are not so easily digested as the simple sugars. The branched nature of polysaccharides, such as starch and cellulose, are the result of links between chains of sugars. The type of link present determines whether or not it will be possible for the horse to digest this form of carbohydrate in the small intestine or not.

Starch

Starch is the primary carbohydrate of interest in our hard feeds. It is a hydrolysable carbohydrate, which can be digested in the small intestine, releasing glucose into the bloodstream. For horses in training this is the most important fast release energy source. Starch is found in all plants, with the highest quantities seen in cereals such as oats, barley and maize.

Composition of cereals commonly used in racing feeds

Starch is made up of two types of sugar chains: amylose and amylopectin, which are formed from glucose units. Amylose itself is easily digested, however amylopectin has a different type of bond connecting each branch, which the enzymes of the small intestine cannot break down. Feed processing, which changes the structure of starch and breaks apart the previously indigestible bonds, is therefore a key factor in ensuring that when starch is fed that the maximum amount of glucose is derived. 

Amylose and Amylopectin 

Feed processing comes in many forms, from simply crushing or rolling the grain to cooking techniques including micronizing, steam flaking, pelleting or extruding. The amount of processing required for what is deemed efficient digestion differs by grain type. Oats have a natural advantage within the cereal group as they can be fed whole, although processing can still improve digestion. Barley, wheat and maize cannot be fed whole or simply rolled. They require cooking to ensure that starch becomes available, and the impact of cooking processes is much greater for these grains. 

The availability of starch is assessed through the amount of glucose released into the blood after feeding. The study below shows the effect of steam cooking maize (corn) compared to two processes that simply change the physical appearance, cracking or grinding. Steam-flaked maize is more available as shown by the greater glucose response. 

Starch is a fast release energy source, being digested in the small intestine, and the term can easily be misunderstood. It does not mean that the horse will suddenly run at top speed nor appear to be fuelled by ‘rocket fuel’. The word ‘fast’ relates to the relatively short time it takes for digestion to occur and glucose to be available. …

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Encouraging and maintaining appetite

By Catherine Rudenko

Encouraging and maintaining appetite throughout a season can become a serious challenge. The best planned feeding program in the world is of no use if the horse simply does not eat as required to sustain performance. There are multiple factors that can lead to poor appetite for horses in training—some relating to health, some relating to physical properties of the feed or forage, along with behavioural considerations. 

What is a normal appetite? 

Before we can fairly state a particular horse has a poor appetite, we must firstly have an idea of what a normal appetite range is. The horse has a given capacity within its digestive tract and an appetite appropriate to this. Horses will typically consume 2-3% of their body weight each day on a dry matter basis—in other words not accounting for fluid intake or any moisture found in the forages. This equates to 10-15kg (or 22-33lbs) per day for a 500kg-weight racehorse. As fitness increases, it is normal for appetite to reduce, and most horses will eat closer to 2% of their body weight. 

The energy requirement of a horse in training is such that we are dependent on a large amount of grain-based ‘hard feeds,’ which for the majority form 7-9kg of the diet each day. With a potential appetite of 10-15kg we are, for some individuals, running close to their likely appetite limit. 

The most immediate effect of a reduction in appetite is the reduction in energy intake. Horses require a large amount of calories, typically 26,000 to 34,000 cal per day when in full training. Comparatively, an average active human will require only 3,000 cal per day. Just one bowl of a racing feed can contain 4,500 cal, and so feed leavers that regularly leave a half or quarter of a bowl at each meal time really can be missing out. Forage is equally a source of calories, and a reduction of intake also affects total calorie intake. 

Physical form of feed and forage

The physical form of the bucket feed can affect feed intake due to simple time constraints. Morning and lunch time feeds are more common times at which to find feed left behind. Different feed materials have different rates of intake—due to the amount of chewing required—when fed at the same weight. To give an example, 1kg of oats will take 850 chews and only 10 minutes to consume in comparison with 1kg of forage taking up to 4,500 chews and 40 minutes to consume. 

Meals that require a high amount of chewing—whilst beneficial from the point of view of saliva production (the stomach’s natural acid buffer)—can result in feed ‘refusal’ as there is simply too much time required. Cubes are often eaten more easily as they are dense, providing less volume than a lighter, ‘fluffier’ coarse mix ration. Inclusion of chaff in the meal also slows intake, which can be beneficial, but not for all horses. Any horse noted as a regular feed leaver ideally needs smaller meals with less chewing time. Keeping feed and forage separate can make a significant difference. 

The choice of forage is important for appetite. Haylage is more readily consumed, and horses will voluntarily eat a greater amount. The study below compares multiple forage sources for stabled horses. 

Another factor relating to forages is the level of NDF present. NDF (neutral detergent fibre) is a lab measure for forage cell wall content—looking at the level of lignin, cellulose and hemi-cellulose. As a grass matures, the level of NDF changes. The amount a horse will voluntarily consume is directly related to the amount of NDF present. 

Analysing forage for NDF, along with ADF, the measure relating to digestibility of the plant, is an important practice that can help identify if the forage is likely to be well received. Alfalfa is normally lower in NDF and can form a large part of the daily forage provision for any horse with a limited appetite. As alfalfa is higher in protein—should it become a dominant form of daily fibre—then a lower protein racing feed is advisable. Racing feeds now range from 10% up to 15% protein, and so finding a suitable balance is easily done. 

B vitamins

B vitamins are normally present in good quantity in forages, and the horse itself is able to synthesise B vitamins in the hindgut. Between these sources a true deficiency rarely exists. Horses with poor appetite are often supplemented with B12 amongst other B vitamins. Vitamin B12 is a cofactor for two enzymes involved in synthesis of DNA and metabolism of carbohydrates and fats. Human studies where a B12 deficiency exists have shown an improvement in appetite when subjects were given a daily dose of B12 (3).

As racehorses are typically limited in terms of forage intake and their hindgut environment is frequently challenged, through nutritional and physiological stresses, it is reasonable to consider that the racehorse, whilst not deficient, may be running on a lower profile. Anecdotal evidence in horses suggests B12 supplementation positively affects appetite as seen in humans. 

Another area of interest around B vitamin use is depression. Horses can suffer from depression and in much the same way as in the human form, this can affect appetite. French researchers investigated the behaviour of depressed horses, those determined as non-reactive or with low reaction to stimuli, against their response to sweetened and novel-flavoured foods. The depressed horses consumed significantly less than normal horses (4). There has been much interest in B vitamins for humans with depression as a low level of B vitamins is linked with depressive behaviour (5). Using a B vitamin supplement may also be beneficial to horses. 

Digestive health

Gastric ulceration is commonly associated with changes in appetite (6). Picky eaters may be responding to the physical effect of feed digestion in the stomach. Racing feeds by design contain a significant amount of starch relative to forages, which horses are designed to consume. Starch fermentation in the stomach produces VFAs (volatile fatty acids), which can damage the stomach lining if the pH level of the upper stomach is lower than normal causing discomfort (7). The ability of the upper stomach to remain within normal parameters relates to forage intake. Normal range is pH 5-7, however with limited forage intake the pH can lower to 4. Once below this level, the squamous tissue may ulcerate for a variety of reasons including VFA production at the time of feeding (8).

The incidence level of ulceration in racehorses is high, with reports of 93% of horses having presence of ulcers (9). Not every individual shows the classical symptoms of ulcers but for any horses with poor appetite scoping for ulcers is recommended. The risk factor for development of ulcers is related to the amount of time spent in training, with every week spent increasing risk 1.7 fold (10). A horse with a change in appetite as the season progresses may not just be the result of increasing fitness but an indicator of an ulcer developing. 

Feed flavouring 

The use of flavouring in feed is another consideration for sparking appetite. Although traditionally mint is used as an addition to feed, more recent research into a broad range of flavours has revealed that horses find other flavours more appetising. In order of preference, horse selectively consumed a fenugreek-flavoured cereal by-product first followed by banana, cherry, rosemary, cumin and carrot before reaching peppermint. When added to mineral pellets, the most common item to be left at the bottom of a feed pot when using a coarse mix for racehorses, the inclusions of fenugreek and banana resulted in pellets being more readily consumed (11). Including a novel flavour may be enough to encourage interest in horses that are apparently off their feed for no reason.

Assessment and recommendations for horses with poor appetite

There are multiple factors that influence appetite, and improving appetite will normally require taking more than one approach to get the best result. …

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No guts, no glory!

By Catherine Rudenko

Can we increase the efficiency of the digestive system through dietary and supplementary manipulation in order to alter performance and recovery? 

The idiom ‘no guts, no glory’, when taken in the literal sense, is quite an appropriate thought for the racehorse. The equine gut is a collection of organs, which when in a state of disease, causes a multitude of problems; and when functioning effectively, it is key for conversion of food to fuel and maintaining normal health. 

In the same way we consider how fuel-efficient our car engines are, what power can be delivered and the influence of fuel quality on function, we can consider the horses’ digestive anatomy. The state of the ‘engine’ in the horse is critical to the output. What is fed or supplemented, and the manner in which we do so, has fascinating and somewhat frightening effects on efficiency and recovery. 

We now, in a human context, have a much better understanding of the relationship between the gut and states of disease. Before disease in a notable sense is present, we see loss of function and reduction in performance. With equines, in recent years, the focus has fallen toward ulceration and the stomach. Now interest is growing into the small and large intestines, looking at factors that influence their performance and in turn how this affects performance on the track. 

In order to consider how we can positively influence gut function, first we need to understand its design and capability, or lack of capability which is more often the problem. The horse, by definition, falls into the category of a large non ruminant herbivore—the same grouping as rhinoceroses, gorillas and elephants. The horse is well designed for a fibre-based diet, as reflected by the capacity of the large intestines, yet we must rely heavily on the small intestine when feeding racehorses. Health and function of both small and large intestines are important and are connected. 

Small Intestine 

The small intestine is a relatively short tube of approximately 25m in length—the same length as found in sheep or goats. The primary role of the small intestine is the digestion of protein, fats and carbohydrates. The workload of this organ is significant and is also time constrained, with feed typically moving at a rate of 30cm per minute (1). The rate of passage is highly influenced by whether the stomach was empty before feeding, or if forage has recently been consumed. The advice of feeding chaff with hard feed is in part to the slow rate of passage and give further time for the processes of digestion. 

The mechanisms for digestion in the small intestine include pancreatic juices, bile and enzymes. Of particular interest are the various enzymes responsible for digestion of protein and carbohydrates— the key nutrients often considered when choosing a racing diet. The ability to digest carbohydrate, namely starch, is dependent on two factors: firstly, form of starch and the level of alpha-amylase—a starch-digesting enzyme found in the small intestine. Whilst the horse is quite effective in digestion of protein, there are distinct limitations around digestion of starch. 

Starch digestion, or lack of digestion in the small intestine, is the area of interest. When feeding, the aim is to achieve maximum conversion of starch in the small intestine to simple sugars for absorption. This is beneficial in terms of providing a substrate readily available for use as an energy source and reducing the ill effects seen when undigested starch moves into the next section of the digestive tract. Alpha-amylase is found in very limited supply in the equine small intestine—the amount present being only approximately 5% of that found within a pig. Despite a low content, the horse can effectively digest certain cereal starches, namely oats, quite effectively without processing. However, other grains commonly used, (e.g., barley and maize [corn]), have poor digestibility unless processed. Flaked, pelleted or extruded cereals undergo a change in starch structure enabling the enzyme to operate more effectively. 

Processing grains whilst improving digestion does not alter the amount of enzyme present in the individual. An upper limit exists on starch intake, after which the system is simply overloaded and the workload is beyond the capacity of the naturally present enzymes. The level is estimated at 2g starch per kilogram of bodyweight in each meal fed. In practice, this translates to 3.5kg (7 ¾ lbs) of a traditional grain-based diet of 28% starch. In bowls, this is roughly 2 bowls of cubes or 2 ¼ bowls of mix—an intake typical of an evening feed. The ‘safe limit’ as a concept is questionable because of other factors involved in starch digestion, including how quickly a horse will eat their feed, dental issues and individual variation in the level of alpha-amylase present. 

In practice, feeding racehorses will invariably test the capacity of the small intestine as the volume of feed required to meet the demands of training is significant, and through time constraints of both horse and human results in a large-sized evening meal. The addition of amylase or other enzymes to the diet is therefore of interest. Addition of amylase is documented to increase digestion of maize (corn)—one of the most difficult grains to digest—from 47.3% to 57.5% in equines (2). Equally, wheat digestion has been evidenced to improve with a combination of beta-glucanase, alpha-amylase and xylanase in equines, increasing starch digestion from 95.1% to 99.3% (3).

Use of enzymes in the diet has two areas of benefit: increasing starch conversion and energy availability, and reducing the amount of undigested starch that reaches the hindgut. The efficacy of the small intestine directly impacts the health of the large intestine—both of which influence performance. 

Large Intestine 

The caecum and colon, of which there are four segments, form the group referred to as the hindgut. Their environment and function are entirely different to that of the small intestine. Here, digestion is all about bacterial fermentation of the fibrous structures found in forages and parts of grains and other feed materials. The time taken to digest foodstuffs is also significantly different to that of the small intestine, with an average retention time of 30 hours. 

The end result of fermentation is the production of fatty acids, namely acetate, butyrate and propionate—the other by-product of fermentation being lactate. The level of fatty acids and lactate produced is dependent on the profile of bacteria found within the gut, which in turn react to the type of carbohydrate reaching the hindgut. There are markedly different profiles for horses receiving a mostly fibre-based diet compared to those with a high-grain intake. 

The interaction between the microbial organisms and metabolism, which directly influences health and disease, is gaining greater understanding. By looking at the faecal metabolome, a set of small molecules that can be identified in faecal samples, and the categories of bacteria in the gut, it is possible to investigate the interaction between the individual horse, its diet and bacteria. Of course, the first challenge is to identify what is normal or rather what is typical of a healthy horse so that comparatives can be made. Such work in horses in training, actively racing at the time of the study, has been carried out in Newmarket. 

Microbiome is a term used to describe microorganisms, including bacteria, that are found within a specific environment. In the case of the horses in training, their microbiome was described before and after a period of dietary intervention. The study evidences the effect on the hindgut of including an enzyme supplement, ERME (Enzyme Rich Malt Extract). The table below shows changes in nine bacterial groups before and after supplementation. 

Along with changes in bacterial abundance, which were relatively small, came more significant changes within the metabolome. The small molecules found in the metabolome are primarily acids, alcohols and ketones. Of particular interest, and where statistical significance was found, were changes in acetic acid and propionic acid evidencing an effect on the digestive process. 

Whilst production of fatty acids is desired and a natural outcome of fermentation, further work is needed to determine what is an optimum level of fatty acid production. This study of horses in training is an interesting insight into an area of growing interest. 

Effects on Performance & Large Intestine Function…

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The Balancing Act

By Catherine Rudenko

Key considerations when reviewing what you feed and if you should supplement

With so many feeds and supplements on the market, the feed room can soon take on the appearance of an alchemist’s cupboard. Feeding is of course an artform but one that should be based on sound science. In order to make an informed decision, there are some key questions to ask yourself and your supplier when choosing what ingredients will form your secret to success. 

Question #1: What is it? 

Get an overview of the products’ intended use and what category of horse they are most suited for. Not every horse in the yard will require supplementing. Whilst one could argue all horses would benefit from any supplement at some level, the real question is do they need it? Where there is a concern or clinical issue, a specific supplement is more likely warranted and is more likely to have an impact. A blanket approach for supplements is really only appropriate where the horses all have the same need (e.g., use of electrolytes).  

Question #2: Is it effective? 

There are many good reasons to use supplements with an ever-increasing body of research building as to how certain foods, plants or substances can influence both health and performance. Does the feed or supplement you are considering have any evidence in the form of scientific or clinical studies? Whilst the finished product may not—in a branded sense—be researched, the active components or ingredients should be. Ideally, we look for equine-specific research, but often other species are referenced, including humans; and this gives confidence that there is a sound line of thinking behind the use of such ingredients. 

Having established if there is evidence, the next important question is, does the feed or supplement deliver that ingredient at an effective level? For example, if research shows 10g of glucosamine to be effective in terms of absorption and reaching the joint, does your supplement or feed—when fed at the recommended rate—deliver that amount? 

There is of course the cocktail effect to consider, whereby mixing of multiple ingredients to target a problem can reduce the amount of each individual ingredient needed. This is where the product itself is ideally then tested to confirm that the cocktail is indeed effective. 

Question #3: How does it fit with my current feeding and supplement program? 

All too often a feed or supplement is considered in isolation which can lead to over-supplementing through duplication. Feeds and supplements can contain common materials, (i.e., on occasion there is no need to further supplement or that you can reduce the dose rate of a supplement). 

Before taking on any supplement, in addition to your current program, you first need to have a good understanding of what is currently being consumed on a per day basis. …

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How has horses' feed changed? Thoroughbred Nutrition Past & Present

By Catherine Rudenko

Feeding practices for racehorses have changed as nutritional research advances and food is no longer just fuel but a tool for enhancing performance and providing that winning edge. 

Whilst feeding is dominantly considered the content of the feed bucket, which by weight forms the largest part of the horse’s diet, changes in forage quality have also played a role in the changing face of thoroughbred nutrition. The content of the feed bucket, which is becoming increasingly elaborate with a multitude of supplements to consider, the forages—both long and short chop and even the bedding chosen—all play a part in what is ‘the feed program’. Comparing feed ingredients of the past against the present provides some interesting insights as to how the industry has changed and will continue to change.

Comparing key profiles of the past and present 

The base of any diet is forage, being the most fundamental need of the horse alongside water. Forage quality and form has changed over the years particularly since haylage entered the market and growers began to focus specifically on equine. The traditional diet of hay and oats, perhaps combined with mash as needed, provided a significantly different dietary intake to that now seen for horses fed a high-grade haylage and fortified complete feed. 

Traditional Diet

• 7kg Oats

• 1kg Mash – comprised of bran, barley, linseed and epsom salt

• 0.5kg Chaff

• Hay 6% protein consumed at 1% of bodyweight

Modern Diet – medium-grade haylage

• 8kg Generic Racing Mix 

• 0.5kg Alfalfa Chaff

• 60ml Linseed Oil

• 60g Salt

• Haylage 10% protein consumed at 1% of bodyweight

Modern Diet – high-grade haylage

• 8kg Generic Racing Mix 

• 0.5kg Alfalfa Chaff

• 60ml Linseed Oil

• 60g Salt

• Haylage 13% protein consumed at 1% of bodyweight

The traditional example diet of straights with bran and hay easily met and exceed the required amount of protein providing 138% of requirement. When looking at the diet as a whole, the total protein content of the diet inclusive of forage equates to 9.7%. In comparison the modern feeding example using a high-grade haylage produces a total diet protein content equivalent to 13.5%. The additional protein whilst beneficial to development, muscle recovery and immune support can become excessive. High intakes of protein against actual need have been noted to affect acid base balance of the blood, effectively lowering blood pH (1). Modern feeds for racing typically contain 13-14% protein which complement forages of a basic to medium-grade protein content very well; however when using a high-grade forage, a lower protein feed may be of benefit. Many brands now provide feeds fortified with vitamins and minerals designed for racing but with a lower protein content. 

Whilst the traditional straight-based feeding could easily meet energy and protein requirements, it had many short-falls relating to calcium and phosphorus balance, overall dietary mineral intake and vitamin intake. Modern feeds correct for imbalances and ensure consistent provision of a higher level of nutrition, helping to counterbalance any variation seen within forage. Whilst forage protein content has changed, the mineral profile and its natural variability has not. 

Another point of difference against modern feeds is the starch content. In the example diet, the ‘bucket feed’ is 39% starch, a value that exceeds most modern racing feeds. Had cracked corn been added or a higher inclusion of boiled barley been present, this level would have increased further. Racing feeds today provided a wide range of starch levels ranging from 10% up to the mid-thirties, with feeds in the ‘middle range’ of 18-25% becoming increasingly popular. There are many advantages to balancing starch with other energy sources including gut health, temperament and reducing risk of tying-up. 

The horse with a digestive anatomy designed for forages has limitations as to how much starch can be effectively processed in the small intestine, where it contributes directly to glucose levels. Undigested starch that moves into the hindgut is a key factor in acidosis and whilst still digested, the pathway is more complex and not as beneficial as when digested in the small intestine. Through regulating starch intake in feeds the body can operate more effectively, and energy provided through fibrous sources ensures adequate energy intake for the work required. 

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All tied up?

By Catherine Rudenko

Tying-up or ER (exertional rhabdomyolysis) is a problem that every yard will encounter at some point in time with reports of 5-7% of the thoroughbred population being affected. ER is the general term used to cover two main forms of tying-up, acute or recurrent. ER by definition relates to the breakdown of striated muscle fibres following exercise. These fibres connect to the bone allowing movement of the skeleton. Damage causes anything from mild stiffness to the inability to move.

With much still unknown about the condition, the focus falls on reducing risk and ongoing management of those affected with recurrent form. The main area for intervention and management relates to feeds and feeding practices, an area that can be directly controlled by the yard and adjusted as needed for the individuals most affected.

Acute Exertional Rhabdomyolysis

The acute form is typically caused through factors external to the muscle rather than their being an intrinsic muscle defect.

Most commonly seen when the horse is adapting to a new level of work and the intensity or duration is too strenuous. Where speed work is concerned, the most likely cause is a depletion of cellular high energy phosphates, the muscles’ energy supply, combined with lactic acidosis. Where endurance work is concerned, depletion of intracellular glycogen—the stored form of glucose often combined with over-heating and electrolyte imbalances—is the common cause.

The other key factor for an acute episode is dietary energy intake being excessive to the current level of work. The use of high starch feeds to supply energy for horses in training is a common practice with grains, traditionally oats, forming the basis of such feeds. In the early stages of fitness work, an over-supply of energy relative to need, particularly when starch forms a large part of the diet, is a risk factor.

Recurrent Exertional Rhabdomyolysis

This form of ER, where episodes are frequent and often seen even at low levels of exercise, has led to the suggestion that much like humans, there is an inherited intrinsic muscle defect. Such defects would predispose the horse to ER. Documented defects relevant to thoroughbreds include a disorder in muscle contractility or excitation contraction coupling, whereby muscle fibres become over-sensitive and normal function is disrupted.  

Risk factors for ER in horses with the recurrent form include stress or high excitement during exercise, periods of jogging (10-30 minutes), infrequent exercise and over-feeding of energy in a high starch format relative to need.

Dietary Considerations for ER

The amount of energy fed and the type of energy fed are important considerations whether looking to avoid an acute feed related episode or considering the management of a horse with the recurrent form.

Other nutrients often talked about when managing ER include vitamin E, selenium and electrolytes. Historically the inclusion of vitamin E and selenium were considered important for the prevention of further episodes, however there is no evidence to support such use. A case of deficiency in either of these nutrients may well put the horse at a disadvantage and could perhaps create a state where occurrence is more notable; however, with the advent of fortified and balanced complete bagged feeds, such nutrients are normally supplied in more than adequate amounts. Their role as antioxidants which function to ‘mop-up’ damaging free radicals generated through training is where their use can benefit any horse at this level of work. The use of additional vitamin E is also recommended when increasing the fat content of the diet—a common practice when feeding horses with recurrent ER.

Electrolytes do play an important role in normal muscle function, and any deficiency noted in the diet should be corrected. Identifying a need in the diet is more easily done than determining if the individual horse has a problem with absorption or utilisation of the electrolytes. A urinary fractional excretion test (FE) will highlight issues, and subsequent correction through the diet to return the horse to within normal ranges may offer some improvement. However, it is important to note that for horses with recurrent ER, where an intrinsic muscle defect is present, the research to date has shown no electrolyte imbalances or differences between such horses and unaffected horses.

Quantifying ‘Low Starch and High fat’ Feeding

The recommended practice for management of ER is a reduction in starch and an increase in fats. This practice has two ways of benefiting the horse: a reduction in ‘spookiness’ or reactivity and a positive effect on muscle damage as seen by lower CK (creatine kinase) levels following exercise.

Positive effects on lowering CK levels were found when a higher proportion of the energy fed came from diets higher in fats and lower in non-structural carbohydrates (starches and sugars). The effect was noted when fed at 4.5kg/day—an amount easily reached and normally surpassed when feeding horses in training. The beneficial diet provided 20% of energy from fats and only 9% from starches and sugars compared to the more traditional sweet feed diet providing 45% of energy from starches and sugars and less than 5% from fats.

Finding Fats

Top dressing of oils will increase fat in the diet - with a normal intake of up to 100 mls per day. Although the horse can digest higher amounts, palatability usually restricts a higher intake. Pelleted or extruded fat sources are increasingly popular as alternatives to oils for their convenience of feeding and palatability. Straight rice bran and blends of materials such as rice bran, linseed and soya are available from most major feed companies. Oil content will typically range from 18-26% providing 180g-260g of oil per kilogram as fed.  

Racing feeds will also provide oil in the diet; content is quite varied typically from 4-10% providing 40g-100g per kilogram as fed. Hay and haylage also contains oil at a low level, typically 2% providing just 20g per kilogram on a dry matter basis.

Choosing Carbohydrates

Traditional feeding based on oats and other whole grains will have a higher starch content than feeds using a combination of grains and fibres. Levels of starch found in complete feeds and straights have a broad range from as low as 8% in a complete feed, specifically formulated to have a low starch content, and up to in excess of 50% for straights such as barley and naked oats.

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April - June 2019, issue 65 (PRINT)

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