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Racing power - supporting muscular effort through nutrition

Dr Catherine Dunnett (European Trainer - issue 19 - Autumn 2007)

The powerhouse for a horse in training is found in its large muscle mass. Whilst genetic makeup within the Thoroughbred breed has a large impact on a horse’s innate racing ability, dietary factors will also influence subsequent performance. There are many elements found in a racehorse’s diet that will help to support muscle function. Hydrolysable carbohydrate (sugar and starch), assisted by fermentable fibre, will help to maintain important muscle stores of glycogen (a carbohydrate fuel).

Dietary electrolytes, which are integrally involved in muscle contraction, are essential to offset electrolyte loss in sweat. Key dietary antioxidants such as vitamins E and C and also antioxidant co-factors, such as copper, manganese, zinc and selenium, are also important as part of the body’s antioxidant team which strives to reduce the formation of free radicals or reactive oxygen species, and to limit their damaging effects on the body. Free radical damage has previously been implicated in the process of exercise induced muscle damage.

GLYCOGEN STORES MUST BE REPLENISHED FOLLOWING EXERCISE

One of the most important functions of the diet is to replenish the horse’s energy stores in muscle on an ongoing basis. A racing ration needs to support the synthesis of glycogen to maintain the store of this important fuel, which is used in increasing amounts during exercise. Glycogen, which consists of a large branched chain of glucose units, is stored in both skeletal muscle and the liver and it represents one of the largest potential energy stores in the body. Horses being natural athletes, have a relatively large muscle glycogen store when compared to other species. As the glycogen content of horse muscle is influenced by the proportion of different muscle fibre types present, this means that there is a genetic influence on the overall glycogen content. Fast twitch fibres (Type IIb), which are found in increased numbers in talented sprinting horses, store relatively more glycogen than the slower type I and type IIa fibres. However, both diet and training can influence the level of glycogen stored in muscle. Exercise training for example has been reported to increase muscle glycogen content by 30-60% in horses. Logically, diet should have a significant effect on the storage of muscle glycogen as it provides the building blocks for glycogen synthesis. Glycogen can be synthesised efficiently from dietary starch, which is another polymer of glucose found in cereals. Glycogen can also be produced from certain glycogenic amino acids, released from the protein content of feed. In addition, propionic acid, which is a significant volatile fatty acid produced in the horse’s hindgut during the fermentation process, can also ultimately be converted to muscle glycogen.

In terms of the day to day diet, starch is by far the most direct and most efficient precursor for glycogen and so it is therefore not surprising that cereals, which are high in starch, have been the mainstay of racing diets for many years. In recent years we have seen the introduction of racing feeds that are lower in starch and sugar than traditional racing rations, with a greater emphasis being placed on digestible fibre and oil as energy sources. Whilst there are many health benefits attributable to this type of diet, the effect of changing the level of starch in the diet on muscle glycogen should always be considered.

MUSCLE GLYCOGEN - AN IMPORTANT FUEL BUT NOT THE KEY FACTOR IN FATIGUE

Muscle glycogen is a major source of energy (ATP) to working muscle during intense exercise, which is characteristic of racing. The amount of muscle glycogen used during training or racing will depend on its rate of utilisation, which in turn is affected by the speed and duration of the exercise undertaken. In general terms, the higher the speed, the faster muscle glycogen is broken down and used.

The duration of fast exercise is normally curtailed, which limits the overall amount of glycogen used. During slower work, although the rate of glycogen utilisation is much lower, exercise can usually be continued for a much longer time allowing more glycogen to be utilised overall (see figure 1). Total muscle glycogen content can be reduced by about 30% during a single bout of maximal exercise in horses. However, as muscle is a mix of different fibre types, the depletion of glycogen in individual fibres may be greater than this depending on the pattern of fibre recruitment during the exercise. Studies, however, have shown that even the IIB muscle fibres, which use glycogen at the fastest rate, are not totally depleted of glycogen following racing.

This supports the notion that although glycogen is an important fuel source for racehorses, glycogen depletion is not the most important factor in fatigue. However, exercise studies do suggest that power output and exercise performance can be decreased in horses where muscle glycogen has failed to be adequately replaced following a previous race or piece of hard work. This was the conclusion drawn by Lacombe and co-workers (2001) who reported that horses with replete muscle glycogen stores were able to run for longer periods during a maximal exercise test compared to horses whose muscle glycogen level remained low following a previous exercise bout. Whilst there are always horses that will buck the trend, this research emphasises the need to allow a suitable period of time between races, but also between bouts of fast work and subsequent racing to allow muscle glycogen stores to be replenished.

In contrast to human athletes, muscle glycogen replenishment in horses is relatively slow. Following racing or a hard work, research suggests that muscle glycogen can take up to 72 hours to return to pre-exercise levels when a traditional high cereal racing ration is fed. Certainly research carried out in the past 3 years would suggest that a high glycemic racing ration would be better placed to support glycogen replenishment more quickly following racing or hard work. There are many factors that affect the glycemic response to feed, which in simple terms describes the relative rise in blood glucose following feeding.

The starch and sugar content of a feed, however, is one of the most significant factors affecting glycemic response. Feeds that are high in starch and sugar e.g. a high cereal-containing mix produce a greater glycemic response compared with feeds that are very low in starch and sugar e.g. a forage only ration. Rate of glycogen synthesis following a glycogen depleting exercise bout was significantly higher in horses fed a high glycemic diet compared to those fed a very low glycemic control diet (Lacombe et al 2004, Lacombe et al 2006). In addition, absolute glycogen concentration in muscle was significantly higher both 48 and 72 hours following exercise in the high glycemic group compared to the control horses and muscle glycogen concentration had returned to pre-exercise levels following 72 hours. The benefit of a high glycemic diet for glycogen repletion does, however, appear to be time dependent. Jose-Cunelleras (et al 2006) reported a minimal difference in glycogen repletion in the first 24 hours following a glycogen depleting exercise bout between horses that were fed a high glycemic feed compared with a group where feed was withheld for 8 hours and another group of horses where only hay was fed.

A recent study also concluded that the route of administration of carbohydrate given post-exercise significantly affects the rate of glycogen replenishment. Horses that were given an intravenous infusion of glucose following exercise exhibited significantly greater glycogen storage rates and glycogen concentration in the first 6 hours following exercise compared to horses fed a similar quantity of glucose orally. In fact, the repletion of glycogen in response to oral glucose was minimal over this time period compared to the unsupplemented control horses (Geor et al 2007). Whilst it is difficult to draw direct comparisons with feeding practices used in racing, it is worth appreciating the possible differences in the rate of glycogen repletion when very high glycemic feeds are fed compared to very low glycemic feeds. The reality in many training yards I would suspect lies somewhere between these two extremes.

LOW GLYCEMIC DIETS CAN OFFER RACEHORSES MANY BENEFITS

There are many health-related benefits to feeding a ration that is lower in starch and sugar. However, one should be mindful of muscle glycogen when considering horses that are consistently fed a low glycemic diet. Specifically horses may be fed this type of ration because they are behaviourally more manageable, or because a specific condition such as the muscular disease recurrent exertional rhabdomyolysis (tying up) (RER) is present. A low starch diet is actively encouraged for horses that suffer from RER. McKenzie (et al 2003) reported that plasma creatine kinase activity (CK), elevations of which can indicate muscle damage, was significantly reduced following exercise in RER horses fed a low starch high fat diet versus a high starch low fat diet. In addition, lower resting heart rates have also been reported in horses fed a low starch high fat diet compared to the reverse.

A lower resting heart rate may be beneficial especially in RER horses where it reflects a calmer horse as stress has been implicated as a trigger factor for the condition. The current thinking on feed for horses with RER continues to be a low starch and sugar diet supplemented with oil. It is also important that the diet is well balanced, especially with respect to calcium and phosphorus. Adequate electrolyte provision is equally important, as is the intake of antioxidants such as vitamin E and other related trace minerals such as selenium. Any potential individual limitation in mineral or electrolyte absorption and retention should be investigated further with veterinary assistance in order that individualised adjustments can be made to the diet.

A SUPPORTING ROLE FOR PROTEIN IN MUSCLE RECOVERY

Whilst we are all no doubt aware that the amino acids that make up protein are important for muscle development and repair, protein and its constituent amino acids have received very little attention in horses in terms of their potential to limit exercise induced muscle damage and aid muscle recovery. In human athletes, co-consumption of a protein and carbohydrate drink during and after exercise appears to limit exercise induced muscle damage, ultimately allowing faster recovery (Baty et al 2007; Saunders et al 2004). Recent introduction of ingredients containing partially hydrolysed protein may improve absorption of these amino acids and peptides possibly offering further benefit. Finally, some nutraceutical ingredients including carnitine and creatine have been hailed as being beneficial to muscle function and recovery in human athletes. Creatine, which has been studied in the horse, has failed to offer any great advantage, largely due to its poor absorption. Likewise, carnitine has been reported to improve muscle blood flow during exercise in humans, helping to reduce muscle damage. However, this aspect has not as yet been investigated in horses and previous dietary studies with carnitine were not unequivocal about the ability of oral carnitine to increase muscle carnitine content.

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Forage - So much more than just a filler

Too often thought of as just a filler or occupational therapy to while away the time between hard feeds, forage is worth so much more than that. Simply feeding an inadequate quantity of forage, or choosing forage that has an inappropriate nutrient profile, or is of poor quality can have a negative impact both on health and performance in racehorses.

Dr Catherine Dunnett (01 July 2007 - Issue Number: 4)

By Dr Catherine Dunnett

Too often thought of as just a ‘filler’, or occupational therapy to while away the time between hard feeds, forage is worth so much more than that. Simply feeding an inadequate quantity of forage, or choosing forage that has an inappropriate nutrient profile, or is of poor quality can have a negative impact both on health and performance in racehorses.

Inappropriate choice of forage and its feeding can easily lead trainers down the slippery slope towards loose droppings and loss of condition. Forage can also have a significant impact on the incidence and severity of both gastric ulcers and respiratory disease, including inflammatory airway disease (IAD) and recurrent airway obstruction (RAO).

When choosing forage the main elements to consider are
• Good palatability to ensure adequate intake

 • Adequate digestibility to reduce gut fill

 • Fitness to feed to maintain respiratory health

 • A profile of nutrients to complement concentrate feeds

FORAGE CAN ONLY BE GOOD WHEN PALATABLE 

Palatability is a key issue, as even the best forage from a quality and nutritional standpoint is rendered useless if the horses do not eat sufficient quantities on a daily basis. Palatability is a somewhat neglected area of equine research and so we largely have to draw on practical experience to tell us what our horses like and what they don’t. Some horses appear to prefer softer types of hay, whilst others prefer more coarse stemmy material. Many horses readily consume Haylage, whilst some trainers report that other horses prefer traditional hay. Apart from the physical characteristics, the sugar content of hay or haylage may affect its palatability. Forage made from high sugar yielding Ryegrass is likely to have a higher residual sugar content compared with that made from more fibrous and mature Timothy grass.

Some interesting research carried out a few years ago by Thorne et al (2005), provided some practical insight into how forage intake could be increased in the reluctant equine consumer. This work reported that the amount of time spent foraging (which will increase saliva production), was increased when multiple forms of forage were offered to horses at the same time. From a practical viewpoint this can be easily applied in a training yard and it should help to increase the amount of forage consumed. For example, good clean hay could be offered together with some haylage, and a suitable container of alfalfa based chaff or dried grass all at the same time.

A Healthy Intake 

Racehorses in training often eat below what would be considered to be the bare minimum amount of forage to maintain gastrointestinal health. Whilst sometimes this is due to the amount of forage offered being restricted, in other instances it is because the horses are limiting their own intake. This may be due to either their being over faced with concentrate feed, or due to unpalatable forage being fed. Establishing a good daily intake of forage during the early stages of training and then maintaining the level through the season is important. Typically the absolute minimum amount of forage fed should be about 1% or 1.2-1.5% of bodyweight for hay or haylage, respectively. This equates to 11lb of hay or a rounded 15.5lbs of haylage for an average sized horse (1100lbs). The weight of haylage fed needs to be greater than that of hay due to the higher water content of the latter.

 Intake of haylage needed to achieve a similar dry matter intake to 11lbs of hay

Moisture Dry Matter Weight of forage Percentage Increase above hay Hay (Average) 15% 85% 11lbs  Haylage 1 30% 70% 13lbs 20% Haylage 2 45% 55% 16.5lbs 50%
The dry matter of haylage needs to be consistent to allow a regular intake of fibre and reduce the likelihood of digestive disturbance or loose droppings. Ideally trainers should be aware of any significant change in dry matter, so that they can adjust the intake accordingly.

Forage intake is restricted in racehorses to firstly ensure that a horse consumes adequate concentrate feed to meet their energy needs and requirement for vitamins and minerals within the limit of their appetite. Secondly, the amount of forage fed is restricted in order to minimise ‘gut fill’ or weight of fibre and associated water in the hindgut, as this will restrict their speed on the racetrack.

BUT… inadequate amounts of forage in a horses’ diet has such a negative effect on health that the minimum amount fed must be kept above recognised ‘safe limits’. Choosing an early cut forage that is less mature and with more digestible fibre means that the ‘gut fill’ effect is lessened. In addition, horses can always be fed more forage during training with the daily quantity being reduced (within the safe limits) in the few days before racing where this is practical.

FITNESS TO FEED 

Quality of forage, in terms of its mould, yeast and mycotoxin load, can have a major impact on respiratory health. A recent Australian report (Malikides and Hodgson 2003) highlighted the cost of inflammatory airway disease (IAD) in horses in training, in terms of loss of training time and of potential earnings, together with the associated cost of veterinary treatment. They estimated from their study group that in Australian racing up to 33% of horses in training can have lower airway inflammation, yet show no overt clinical signs.

Type and therefore quality of forage, as well as the quality of ventilation were singled out as the most significant risk factors in the development of IAD.
Forage is potentially a concentrated source of bacteria, mould spores and even harvest mites. Hay that has heated during storage, or that has been bailed with a high moisture content is likely to provide a greater load of these undesirable agents that can harbour substances that promote airway inflammation, such as endotoxin.

Purchasing good quality and clean forage from a respiratory perspective will certainly reduce the pressure placed on young racehorses’ respiratory systems. However, how does one achieve this?

• Microbiological Analysis – the price paid for a microbiological analysis of a prospective batch of hay is a worthwhile cost when the consequences of poor hay are considered.

Assuming the analysis is favourable, purchasing a larger batch for storage gives further peace of mind and spreads the cost further, providing of course that the storage conditions are appropriate.

Interpretation of the microbiology results as CFU/g (colony forming units/gram) for moulds, yeasts and Thermophillic actinomycetes is not difficult. As a rule of thumb the lower the CFU count the better. Whilst a very low mould or yeast count (<10-100) should not usually cause concern, more consideration of the merits of a batch of forage should be triggered by a CFU count that reaches 1000-10,000. Certainly if any Aspergillis species of mould are identified the alarm bells should be ringing. Aspergillis Fumagatus has particular association with respiratory disease including ‘Farmers Lung’ in humans.

Storage

A suitably sized storage area will allow storage of a good-sized batch of your chosen forage giving consistency through the season. It makes financial sense for the welfare of racehorses to make adequate provision for a good-sized storage area. Third party storage is also sometimes an option where this is not available on site.

Forage merchant or farmer?

A good working relationship with one or more farmers or forage merchants is essential to be able to consistently buy good hay. They need to know what you want to buy and you need to be able to rely on them to provide a high quality product through the season.

Forage merchant Robert Durrant stands by the principle that “A good forage merchant should be able to supply a trainer with the same high standard of hay for much if not all of the season”.
He adds that in his opinion “American hay English hay or haylage are all good options when they have been made well and the quality is high, but the quality of the American hays are consistently more reliable.”

NUTRITIONAL CONSIDERATIONS 

The nutritional contribution made by forage should complement that made by the concentrate feed. Most racing rations are high in energy, high in protein and low in fibre. Therefore a suitable forage needs to be contrastingly high in digestible fibre with a limited level of energy and protein. However, where you have sourced early cut hay or haylage that is more digestible and higher in energy and protein, the concentrate feed intake should be adjusted to account for this. This will help to avoid the issue of over feeding of energy or protein. An excess of energy can result in undesired weight gain or over exuberance, whilst an excessive intake of protein at the very least increases the excretion of ammonia, which is a respiratory irritant. Whilst it is important to know the calcium and phosphorus content of forage, the trace mineral content is less significant as the concentrate feed will meet the majority of the horse’s requirement. The exception to this, however is where a batch of forage is identified as having a severe excess of one particular element, e.g. Iron which can reduce the absorption of copper.

Much emphasis is placed on finding an optimum concentrate feed and associated supplements, to enhance the diet of horses in training. The same emphasis should ideally be placed on a trainer’s choice of forage. Forage can so easily make or break the best thought out feeding plan.

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Nutritional Ergogenic aids for horses - boosting performance

Dr Catherine Dunnett (01 July 2007 - Issue Number: 4)

By Dr Catherine Dunnett

DEFINITION
Ergogenic is defined as ‘work producing’. An ergogenic aid is therefore some system, process, device or substance than can boost athletic performance in some fashion, such as speed, strength or stamina. Broadly speaking there are five categories of ergogenic aids: biomechanical, physiological, pharmaceutical, psychological, and nutritional.
From an athletic perspective ergogenic aids may - enhance the biochemical and therefore physiological capacity of a particular body system leading to improved performance,  alleviate the psychological constraints that can limit performance   accelerate recovery from training and competition.

 This article will focus upon the use of nutritional supplements that are marketed or currently being researched for their efficacy in improving athletic performance in horses.

HOW DO THEY WORK?

In principle nutritional ergogenic aids can enhance exercise performance in horses in a variety ways, depending on the nature of the particular supplement. For example an ergogenic aid might -

Enhance the lean mass of a horse by reducing body fat content whilst maintaining muscle mass, leading to an improved power to weight ratio  Improve the ability to counter lactic acid production or accumulation – producing a slower fatigue process in muscle  Increase muscle mass – resulting in increased power or strength  Increase the transport of oxygen around the body  Improve the efficiency of utilisation of body fuels such as fat, glucose and glycogen  Increase the storage of fuels within the body  Enhance the storage and utilisation of high-energy phosphates used in the early stages of fast exercise

WHAT’S ON THE MARKET?

A vast array of supplements are promoted as being effective ergogenic aids to the training and racing of horses. The table below offers an overview of the global ergogenic aids ‘catalogue’ but is by no means intended to be an exhaustive list.
 Ergogenic effects in horses and humans for dietary supplements marketed for use in performance horses

Proven* beneficial effect in horses Proven* beneficial effect in humans but not horses

No unequivocal ergogenic effect in either species   ß-hydroxy-ß-methylbutyrate (HMB) Creatine Gamma-oryzanol  Carnitine Dimethylglycine (DMG)  Trimethylglycine (TMG)  Ribose  Chromium  Stabilised oxygen  Ubiquinone (Co-enzyme Q10)  Branched chain amino acids (BCAA)  Prohormones

* Based on data produced from scientific trials, rather than anecdotal evidence.
 Creatine

This success largely stems from the fact that, unusually, it is a supplement that works! Admittedly, its effectiveness varies across different sporting disciplines. It has proven especially beneficial in sporting activities of comparatively short duration, such as the athletic disciplines of sprinting and jumping, but also in sports that require very high levels of power production as in rowing, swimming and track-based cycling.

Creatine accomplishes this performance enhancement, firstly by elevating the levels of high-energy phosphates, ATP (adenosine triphosphate) and PCr (phosphocreatine), stored in muscles. Secondly, creatine can enhance the effect of training; i.e. it boosts the responsiveness of the muscles to stimuli generated by training. This is often observed as increased muscle mass that arises from elevated production of the major muscle protein myosin and from enhanced levels of localised growth factors.

The benefits of creatine supplementation in training and competition have not passed the equine world by, and a number of products are marketed specifically for horses. Unfortunately however, despite the positive claims made for these equine products they are not supported by scientific evidence. Indeed the opposite is the case. Sewell and co-workers in the UK and Essen-Gustavssen’s group in Sweden have conducted three rigorous placebo-controlled studies in horses.

No positive effects of creatine supplementation on performance were found when parameters including time-to-fatigue, high-energy phosphate depletion and lactic acid production were measured. The underlying cause for lack of efficacy in horses is due to poor absorption of creatine from the equine gut, leading to inadequate levels being attained in the muscles.

Even if a strategy could be devised to deliver creatine effectively to the muscle, some researchers are of the opinion that there would still be no effect. They form this view on the basis that in comparison with humans the horses is an elite athlete wherein the level of creatine in equine muscle is at or very near to the physiological upper limit.
Carnitine

Carnitine is another well-known dietary supplement widely marketed as an ergogenic aid in human sports nutrition and within the equine industry. The role of carnitine in exercise in humans and horses has been researched for almost 20 years. The biological actions of carnitine that make it central to exercise include:

Directly: transport of fats into muscle mitochondria where they can be used aerobically (oxidised) to generate ATP

Indirectly: increase aerobic utilisation of glucose to produce ATP

Indirectly: reduce lactic acid production (acidosis)

Some research does indicate a positive effect of carnitine supplementation on exercise performance in human athletes, however there are other studies that seem to indicate the opposite.

Conflicting research results have also been found for horses. Studies carried out by Foster and Harris in Newmarket during the 1990s showed that dietary supplementation could increase carnitine levels circulating in the blood, but did not appear to affect the levels in the muscles.

In 2002 Rivero and his fellow researchers at the University of Cordoba conducted a placebo-controlled study into the effect of carnitine supplementation in 2-year-old horses when used in conjunction with an intensive 5 week long training programme. Improved muscle characteristics were seen in the carnitine-supplemented group of horses, including a 35% increase in the proportion of fast-contracting (type IIA) muscle fibres, a 40% increase in the number of capillaries supplying blood to the muscle and an 11% increase in the level of glycogen stored in the muscle. After a let down period of 10 weeks most of these improvements were reversed. It was concluded that carnitine supplementation enhanced the training effect on muscles and that this could improve performance.

Despite the large number of studies conducted over the years the balance of evidence does not yet allow a consensus to be reached on whether carnitine improves performance in horses (and humans) or not. Of course this does not rule out a beneficial effect, and Rivero’s study would seem to be encouraging.

Gamma-Oryzanol

Gamma-oryzanol is not as the name implies a single substance, but is a mixture of chemicals, mainly ferulic acid esters, derived from rice bran. It has been popularised as a potent anabolic agent, i.e. a substance that promotes muscle growth leading to increased strength and speed. Gamma-oryzanol has been employed in equine and human athletes in the belief that it elicits increased testosterone production and stimulation of growth hormone. To date there is no published research describing the effects of gamma-oryzanol on exercise performance in horses, so in an effort to judge its potential efficacy we have to draw upon comparative studies in humans and other animals.

Efficacy for gamma-oryzanol is debatable, as it is poorly absorbed from the digestive tract. What is more when given to rats, contrary to popular belief, it is reported to actually suppress endogenous growth hormone and testosterone production. Research carried out in humans fed 0.5g per day of gamma-oryzanol showed no improvement in performance, nor indeed any change in the levels of testosterone, growth hormone, or other anabolic hormones even after 9 weeks of supplementation. Thus in summary, no scientific evidence exists to support the anabolic effects ascribed to gamma-oryzanol.

Dimethylglycine (DMG) and trimethylglycine (TMG)

Both DMG and its precursor TMG cannot be regarded as new supplements having been researched briefly in the late 1980s with a single research report being published.
Rose and colleagues at the University of Sydney’s veterinary department looked into the potential benefit of DMG on heart and lung function, and lactic acid production in Thoroughbreds during exercise. In this placebo-controlled trial DMG was fed twice daily to a group of thoroughbred horses that underwent a standardised exercise test at varying intensities before and after supplementation with DMG or the placebo. On completion of the trial it was concluded that DMG produced no measurable improvement in any of the parameters, and that it exerts no beneficial effects on heart and lung function or lactic acid production during exercise. Warren and co-workers following experimental evaluation of TMG as an ergogenic aid came to a similarly negative conclusion.

ß-Hydroxy-ß-methylbutyrate (HMB)

HMB is one of the few ergogenic aids available for use in performance horses that is supported by at least some credible science. Significantly, research developing and validating the use of HMG in horses (and farm animals) was instigated and carried forward over a number of years at Iowa State University, USA, and the concept and methodology are protected by US patents. HMB is a metabolite of leucine, one of the so-called branched-chain amino acids (BCAAs), that are themselves often touted as ergogenic aids, although there is no convincing evidence to support such a claim.

Research seems to indicate that HMB supplementation when employed in conjunction with an effective training regime can benefit equine performance in a number of ways:
 Enhance muscle development and increase lean muscle mass and strength by reducing the proportion of energy needed for exercise that is derived from protein and increasing the proportion derived from fat.  Reduce muscle damage (catabolism) during and after exercise and accelerate muscle repair. Some research suggests that HMB is a structural constituent of muscle cells that is destroyed under the physiological stress of exercise.   Increase aerobic capacity (oxygen utilisation) in performance horses by increasing both haemoglobin and the proportion of red blood cells in the blood (haematocrit).

When HMB use was evaluated in practice under real racing and training conditions it appeared to reduce muscle damage, and to improve oxygen use by the muscles and overall performance.

NEW DEVELOPMENTS

Ribose

Ribose is a potential new dietary ergogenic aid that began to be studied in 2002. It is a sugar that is the central component of ATP. As ATP stores are depleted during intense exercise in horses, it was thought that supplementing the horses’ diet with ribose might lessen the loss of ATP during exercise and enhance its regeneration during recovery. Kavazis and his colleagues at the University of Florida conducted two placebo-controlled studies in Thoroughbreds. In these studies ribose was fed twice daily as a top dressing for two weeks to a group of trained horses. The data from these two studies was contradictory and thus no conclusions can be easily drawn. However, two studies in humans have shown no positive effect of ribose supplementation on exercise performance. The balance of available evidence therefore suggests that ribose provides no ergogenic benefit in performance horses.

Bioavailable stabilised oxygen

It is suggested that this bioavailable oxygen is absorbed from the stomach and intestine into the blood stream, however these tissues have not evolved for this purpose unlike the lungs. Even if we assume that all the oxygen from e.g. (100 mL) was taken up into the blood, the added benefit would be very small; 100 mL is roughly equivalent to 20 litres of oxygen. In comparison, an average horse exercising at racing speeds breathes in more than 2000 litres of air (420 litres of oxygen) every minute and the muscles use 75 litres of oxygen over the same period. We should also remember that for a normal healthy horse the blood is 98% saturated with oxygen.

 WHERE NEXT?

The future direction for nutritional ergogenic aids is extremely difficult to predict as any new developments are likely to mirror advances in our detailed understanding of the basic biochemical and physiological processes that underpin exercise performance. In the past, much of the impetus for equine research in this area developed from human sports nutrition and this is likely to continue in the future. A closing comment to put all of this information into context would be that whilst one should always seek a feasible mechanism of action and proof of efficacy for new products, small numbers of horses used in trials and difficulties in measuring ‘performance’ means that science will not always come up with the absolute answer. 

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Nutritional ergogenic aids for horses

Dr Catherine Dunnett (European Trainer - issue 18 - Summer 2007)

No doubt we are all aware of the plethora of dietary supplements that are now available and that are promoted as offering clear and profound benefits to our horses’ health, general well being and performance. In the latter category are the so-called ergogenic aids. So what are they, and do they work? These are the questions that this article aims to address. It should be made clear however, that as nutritional ergogenic aids are quite often not normal constituents of the equine diet and that they function by affecting one or more of the body systems of the horse, then they are by definition prohibited under the rules and regulations of racing. Consequently, this article neither advocates or seeks to legitimise, the use of the supplements discussed specifically, nor the use of nutritional ergogenic aids generally during training or racing.

DEFINITION

Ergogenic is defined as ‘work producing’. An ergogenic aid is therefore some system, process, device or substance than can boost athletic performance in some fashion, such as speed, strength or stamina. Broadly speaking there are five categories of ergogenic aids: biomechanical, physiological, pharmaceutical, psychological, and nutritional.

From an athletic perspective ergogenic aids may - • enhance the biochemical and therefore physiological capacity of a particular body system leading to improved performance • alleviate the psychological constraints that can limit performance • accelerate recovery from training and competition This article will focus upon the use of nutritional supplements that are marketed or currently being researched for their efficacy in improving athletic performance in horses.

HOW DO THEY WORK?

In principle nutritional ergogenic aids can enhance exercise performance in horses in a variety ways, depending on the nature of the particular supplement. For example an ergogenic aid might - • Enhance the lean mass of a horse by reducing body fat content whilst maintaining muscle mass, leading to an improved power to weight ratio • Improve the ability to counter lactic acid production or accumulation - producing a slower fatigue process in muscle • Increase muscle mass - resulting in increased power or strength • Increase the transport of oxygen around the body • Improve the efficiency of utilisation of body fuels such as fat, glucose and glycogen • Increase the storage of fuels within the body • Enhance the storage and utilisation of high-energy phosphates used in the early stages of fast exercise

WHAT’S ON THE MARKET?

A vast array of supplements are promoted as being effective ergogenic aids to the training and racing of horses. The table to the right offers an overview of the global ergogenic aids ‘catalogue’ but is by no means intended to be an exhaustive list.

CREATINE

Many of us will have heard of creatine in the context of nutrition and sport. It has been the great success story, efficaciously and financially, within the sports nutrition sector from the 1990s to the present. In 2004, for example, gross revenue from creatine supplement sales to sports people within North America alone was estimated at $400 million. This success largely stems from the fact that, unusually, it is a supplement that works! Admittedly, its effectiveness varies across different sporting disciplines. It has proven especially beneficial in sporting activities of comparatively short duration, such as the athletic disciplines of sprinting and jumping, but also in sports that require very high levels of power production as in rowing, swimming and track-based cycling. Creatine accomplishes this performance enhancement, firstly by elevating the levels of high-energy phosphates, ATP (adenosine triphosphate) and PCr (phosphocreatine), stored in muscles. Secondly, creatine can enhance the effect of training; i.e. it boosts the responsiveness of the muscles to stimuli generated by training.

This is often observed as increased muscle mass that arises from elevated production of the major muscle protein myosin and from enhanced levels of localised growth factors. The benefits of creatine supplementation in training and competition have not passed the equine world by, and a number of products are marketed specifically for horses. Unfortunately however, despite the positive claims made for these equine products they are not supported by scientific evidence. Indeed the opposite is the case. Sewell and co-workers in the UK and Essen-Gustavssen’s group in Sweden have conducted three rigorous placebo-controlled studies in horses. No positive effects of creatine supplementation on performance were found when parameters including time-to-fatigue, high-energy phosphate depletion and lactic acid production were measured. The underlying cause for lack of efficacy in horses is due to poor absorption of creatine from the equine gut, leading to inadequate levels being attained in the muscles. Even if a strategy could be devised to deliver creatine effectively to the muscle, some researchers are of the opinion that there would still be no effect.

They form this view on the basis that in comparison with humans the horse is an elite athlete wherein the level of creatine in equine muscle is at or very near to the physiological upper limit. CARNITINE Carnitine is another well-known dietary supplement widely marketed as an ergogenic aid in human sports nutrition and within the equine industry.

The role of carnitine in exercise in humans and horses has been researched for almost 20 years. The biological actions of carnitine that make it central to exercise include: Directly: transport of fats into muscle mitochondria where they can be used aerobically (oxidised) to generate ATP Indirectly: increase aerobic utilisation of glucose to produce ATP Indirectly: reduce lactic acid production (acidosis) Some research does indicate a positive effect of carnitine supplementation on exercise performance in human athletes, however there are other studies that seem to indicate the opposite. Conflicting research results have also been found for horses. Studies carried out by Foster and Harris in Newmarket during the 1990s showed that dietary supplementation could increase carnitine levels circulating in the blood, but did not appear to affect the levels in the muscles. In 2002 Rivero and his fellow researchers at the University of Cordoba conducted a placebo-controlled study into the effect of carnitine supplementation in 2-year-old horses when used in conjunction with an intensive 5 week long training programme.

Improved muscle characteristics were seen in the carnitine-supplemented group of horses, including a 35% increase in the proportion of fast-contracting (type IIA) muscle fibres, a 40% increase in the number of capillaries supplying blood to the muscle and an 11% increase in the level of glycogen stored in the muscle. After a let down period of 10 weeks most of these improvements were reversed. It was concluded that carnitine supplementation enhanced the training effect on muscles and that this could improve performance. Despite the large number of studies conducted over the years the balance of evidence does not yet allow a consensus to be reached on whether carnitine improves performance in horses (and humans) or not.

Of course this does not rule out a beneficial effect, and Rivero’s study would seem to be encouraging. GAMMA-ORYZANOL Gamma-oryzanol is not as the name implies a single substance, but is a mixture of chemicals, mainly ferulic acid esters, derived from rice bran. It has been popularised as a potent anabolic agent, i.e. a substance that promotes muscle growth leading to increased strength and speed. Gamma-oryzanol has been employed in equine and human athletes in the belief that it elicits increased testosterone production and stimulation of growth hormone. To date there is no published research describing the effects of gamma-oryzanol on exercise performance in horses, so in an effort to judge its potential efficacy we have to draw upon comparative studies in humans and other animals. Efficacy for gamma-oryzanol is debatable, as it is poorly absorbed from the digestive tract. What is more when given to rats, contrary to popular belief, it is reported to actually suppress endogenous growth hormone and testosterone production. Research carried out in humans fed 0.5g per day of gamma-oryzanol showed no improvement in performance, nor indeed any change in the levels of testosterone, growth hormone, or other anabolic hormones even after 9 weeks of supplementation.

Thus in summary, no scientific evidence exists to support the anabolic effects ascribed to gamma-oryzanol. DIMETHYLGLYCINE (DMG) AND TRIMETHYLGLYCINE (TMG) Both DMG and its precursor TMG cannot be regarded as new supplements having been researched briefly in the late 1980s with a single research report being published. Rose and colleagues at the University of Sydney’s veterinary department looked into the potential benefit of DMG on heart and lung function, and lactic acid production in Thoroughbreds during exercise. In this placebo-controlled trial DMG was fed twice daily to a group of thoroughbred horses that underwent a standardised exercise test at varying intensities before and after supplementation with DMG or the placebo.

On completion of the trial it was concluded that DMG produced no measurable improvement in any of the parameters, and that it exerts no beneficial effects on heart and lung function or lactic acid production during exercise. Warren and co-workers following experimental evaluation of TMG as an ergogenic aid came to a similarly negative conclusion. ß - HYDROXY- ß METHYLBUTYRATE (HMB) HMB is one of the few ergogenic aids available for use in performance horses that is supported by at least some credible science. Significantly, research developing and validating the use of HMG in horses (and farm animals) was instigated and carried forward over a number of years at Iowa State University, USA, and the concept and methodology are protected by US patents. HMB is a metabolite of leucine, one of the so-called branched-chain amino acids (BCAAs), that are themselves often touted as ergogenic aids, although there is no convincing evidence to support such a claim. Research seems to indicate that HMB supplementation when employed in conjunction with an effective training regime can benefit equine performance in a number of ways: • Enhance muscle development and increase lean muscle mass and strength by reducing the proportion of energy needed for exercise that is derived from protein and increasing the proportion derived from fat. • Reduce muscle damage (catabolism) during and after exercise and accelerate muscle repair. Some research suggests that HMB is a structural constituent of muscle cells that is destroyed under the physiological stress of exercise. • Increase aerobic capacity (oxygen utilisation) in performance horses by increasing both haemoglobin and the proportion of red blood cells in the blood (haematocrit). When HMB use was evaluated in practice under real racing and training conditions it appeared to reduce muscle damage, and to improve oxygen use by the muscles and overall performance.

NEW DEVELOPMENTS RIBOSE

Ribose is a potential new dietary ergogenic aid that began to be studied in 2002. It is a sugar that is the central component of ATP. As ATP stores are depleted during intense exercise in horses, it was thought that supplementing the horses’ diet with ribose might lessen the loss of ATP during exercise and enhance its regeneration during recovery. Kavazis and his colleagues at the University of Florida conducted two placebo-controlled studies in Thoroughbreds. In these studies ribose was fed twice daily as a top dressing for two weeks to a group of trained horses. The data from these two studies was contradictory and thus no conclusions can be easily drawn. However, two studies in humans have shown no positive effect of ribose supplementation on exercise performance.The balance of available evidence therefore suggests that ribose provides no ergogenic benefit in performance horses.

BIOAVAILABLE STABILISED OXYGEN

An unusual ergogenic product has recently appeared that purports to be a bioavailable supplementary source of oxygen. In simple terms, it is water that is apparently treated by a sophisticated electrical process so that it becomes a super-saturated solution of oxygen. It’s described as containing about 20,000 times more oxygen than that found in average tap water. As yet, there appears to be no convincing scientific evidence for this type of product, and what is more the explanation of its action does not seem to be physiologically credible. It is suggested that this bioavailable oxygen is absorbed from the stomach and intestine into the blood stream, however these tissues have not evolved for this purpose unlike the lungs. Even if we assume that all the oxygen from e.g. (100 mL) was taken up into the blood, the added benefit would be very small; 100 mL is roughly equivalent to 20 litres of oxygen. In comparison, an average horse exercising at racing speeds breathes in more than 2000 litres of air (420 litres of oxygen) every minute and the muscles use 75 litres of oxygen over the same period. We should also remember that for a normal healthy horse the blood is 98% saturated with oxygen.

WHERE NEXT?

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Forage - so much more than just a filler

Dr Catherine Dunnett (European Trainer - Issue 18 - Summer 2007)

Forage can also have a significant impact on the incidence and severity of both gastric ulcers and respiratory disease, including inflammatory airway disease (IAD) and recurrent airway obstruction (RAO).

When choosing forage the main elements to consider are

• Good palatability to ensure adequate intake • Adequate digestibility to reduce gut fill

• Fitness to feed to maintain respiratory health

• A profile of nutrients to complement concentrate feeds

FORAGE CAN ONLY BE GOOD WHEN PALATABLE

This work reported that the amount of time spent foraging (which will increase saliva production), was increased when multiple forms of forage were offered to horses at the same time. From a practical viewpoint this can be easily applied in a training yard and it should help to increase the amount of forage consumed. For example, good clean hay could be offered together with some haylage, and a suitable container of alfalfa based chaff or dried grass all at the same time.

A Healthy Intake Racehorses in training often eat below what would be considered to be the bare minimum amount of forage to maintain gastrointestinal health. Whilst sometimes this is due to the amount of forage offered being restricted, in other instances it is because the horses are limiting their own intake. This may be due to either their being over faced with concentrate feed, or due to unpalatable forage being fed. Establishing a good daily intake of forage during the early stages of training and then maintaining the level through the season is important. Typically the absolute minimum amount of forage fed should be about 1% or 1.2-1.5% of bodyweight for hay or haylage, respectively.

This equates to 5kg of hay or a rounded 7kg of haylage for an average sized horse (500kg). The weight of haylage fed needs to be greater than that of hay due to the higher water content of the latter. Intake of haylage needed to achieve a similar dry matter intake to 5kg of hay Moisture Dry Matter Weight of forage % Increase above hay Hay (Average) 15% 85% 5kg Haylage 1 30% 70% 6kg 20% Haylage 2 45% 55% 7.5kg 50% The dry matter of haylage needs to be consistent to allow a regular intake of fibre and reduce the likelihood of digestive disturbance or loose droppings.

Ideally trainers should be aware of any significant change in dry matter, so that they can adjust the intake accordingly. Forage intake is restricted in racehorses to firstly ensure that a horse consumes adequate concentrate feed to meet their energy needs and requirement for vitamins and minerals within the limit of their appetite. Secondly, the amount of forage fed is restricted in order to minimise ‘gut fill’ or weight of fibre and associated water in the hindgut, as this will restrict their speed on the racetrack. BUT… inadequate amounts of forage in a horses’ diet has such a negative effect on health that the minimum amount fed must be kept above recognised ‘safe limits’.

Choosing an early cut forage that is less mature and with more digestible fibre means that the ‘gut fill’ effect is lessened. In addition, horses can always be fed more forage during training with the daily quantity being reduced (within the safe limits) in the few days before racing where this is practical.

FITNESS TO FEED

Forage is potentially a concentrated source of bacteria, mould spores and even harvest mites. Hay that has heated during storage, or that has been bailed with a high moisture content is likely to provide a greater load of these undesirable agents that can harbour substances that promote airway inflammation, such as endotoxin. Purchasing good quality and clean forage from a respiratory perspective will certainly reduce the pressure placed on young racehorses’ respiratory systems.

However, how does one achieve this?

• Microbiological Analysis – the price paid for a microbiological analysis of a prospective batch of hay is a worthwhile cost when the consequences of poor hay are considered.

Assuming the analysis is favourable, purchasing a larger batch for storage gives further peace of mind and spreads the cost further, providing of course that the storage conditions are appropriate. Interpretation of the microbiology results as CFU/g (colony forming units/gram) for moulds, yeasts and Thermophillic actinomycetes is not difficult. As a rule of thumb the lower the CFU count the better. Whilst a very low mould or yeast count (<10-100) should not usually cause concern, more consideration of the merits of a batch of forage should be triggered by a CFU count that reaches 1000-10,000. Certainly if any Aspergillis species of mould are identified the alarm bells should be ringing.

Aspergillis Fumagatus has particular association with respiratory disease including ‘Farmers Lung’ in humans.

• Storage –A suitably sized storage area will allow storage of a good-sized batch of your chosen forage giving consistency through the season. It makes financial sense for the welfare of racehorses to make adequate provision for a good-sized storage area. Third party storage is also sometimes an option where this is not available on site.

• Forage merchant or farmer - A good working relationship with one or more farmers or forage merchants is essential to be able to consistently buy good hay. They need to know what you want to buy and you need to be able to rely on them to provide a high quality product through the season. Newmarket based forage merchant Robert Durrant stands by the principle that “A good forage merchant should be able to supply a trainer with the same high standard of hay for much if not all of the season”. He adds that in his opinion “American hay English hay or haylage are all good options when they have been made well and the quality is high, but the quality of the American hays are consistently more reliable.”

PRO’S AND CON’S

Hay from colder climates e.g. UK, Ireland commonly used quality can be variable usually palatable economical Haylage. Usually clean dry matter can be variable Fermentation inhibits mould growth Need to feed more than hay Feed value often higher May need to adjust hard feed Usually palatable Beware of punctured bales Newmarket trainer James Eustace has used big bale haylage for many years he says “I found it increasingly difficult to reliably source good clean English hay. I am very happy with the haylage, as it is pretty consistent and it provides the dust free option that I wanted.”

Hay from warmer climates e.g. USA / Canada usually very clean May need to adjust hard feed Feed value often higher Premium price Usually palatable Newmarket trainer Ed Dunlop appreciates the advantages of using more than one forage source he says, "American hay gives us the consistent good quality that we need and the horses eat it well. Feeding it alongside other forage gives us the flexibility needed for different horses throughout the season." Alfalfa (High temperature dried or sun dried)

Good adjunct to forage (e.g 1-2kg) High intakes can oversupply protein and calcium Can be used as chaff Leaf fragments can add to dust High feed value & digestibility Less gut fill Many of Forage merchant Robert Durrants clients choose sun dried alfalfa as an extra treat for the horses he says “the horses get a large double handful daily as a treat and they love it.”

NUTRITIONAL CONSIDERATIONS

Whilst it is important to know the calcium and phosphorus content of forage, the trace mineral content is less significant as the concentrate feed will meet the majority of the horse’s requirement. The exception to this, however is where a batch of forage is identified as having a severe excess of one particular element, e.g. Iron which can reduce the absorption of copper. Much emphasis is placed on finding an optimum concentrate feed and associated supplements, to enhance the diet of horses in training. The same emphasis should ideally be placed on a trainer’s choice of forage. Forage can so easily make or break the best thought out feeding plan.

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Feeding during early training - how to minimise problems

Most of the current crop of 2yo’s will now have been broken and are in the early stages of training proper in readiness for the forthcoming flat racing season. This period brings with it numerous problems for trainers and their staff, such as horses with high muscle enzymes, episodes of tying up, respiratory infections, various lamenesses and other skeletal problems or simply over exuberance.

Catherine Dunnett (European Trainer - issue 17 - Spring 2007)

Whilst such issues have many contributory factors, a good basal diet, with carefully selected extras can help to minimise some of these niggling problems. Overfed horses can become fat or too excitable During breaking, and pre- and early training the emphasis from a nutritional perspective should be on adequate but not excessive energy intake, whilst ensuring that a balanced diet is provided in terms of vitamins, minerals and quality protein. An overfed horse becomes either fat and so difficult to slim down for racing, or badly behaved and excitable, and thus more prone to injure itself or its rider. To avoid excitability, good quality hay or haylage fed in increased amounts will not only help to reduce the reliance on concentrate feeds, but may also reduce ulceration, especially in horses in their first season of race training. There are several concentrate feeds manufactured specifically for horses in early training or during a ‘lay off’ period. These are generally lower in energy than racing feeds, but still ensure an adequate intake of quality protein for young horses and provide a more concentrated source of vitamins and minerals, given that the intake of feed can be quite low at this time. Sometimes a more economical alternative to these tailored feeds would be a good quality low energy mix or cube, manufactured for the mainstream horse market.

However, reassurance should always be sought from the manufacturer concerned on the suitability of the main ingredients, including the protein and fibre sources and vitamin and mineral level for a horse in pre or early training. An further advantage of these two concentrate feed types for this stage of training, is that the energy provided is derived largely from digestible fibre and sometimes oil, with less emphasis on cereal starch. This is potentially beneficial for behaviour, and also for horses with a predisposition for tying-up or ‘set fast’. Not every raised muscle enzyme is a ‘set fast’ Raised blood levels of the muscle enzymes AST (aspartate aminotransferase) and CPK or CK (creatine kinase) are common place during early training. These enzymes are present at much higher levels in muscle cells than other tissues and therefore their leakage into the blood is considered indicative of muscle damage. The complication is that although muscle damage can result from an ongoing metabolic issue such as tying up, it may also occur as the result of transient over exertion. High AST and CK’s in blood are not always an indication of a horse having tied up and some horses that exhibit these blood results in the early stages of training will often work through it as training progresses.

Care should obviously be taken with horses, who show clinical signs of having tied up on one or more occasion. For such horses, diagnosis early in the season is beneficial, as their diets can be scrutinised more closely and key changes implemented that can in many instances reduce the severity or frequency of such attacks. These horses will often benefit from being fed a basal ration that is very low in starch (typically less than 15%) and so equally will need to be high in digestible fibre and oil to ensure adequate energy intake during training. Current research into tying up cannot yet explain why this dietary change helps, but widespread experience suggests that in many instances it does. Stephanie Valberg from the University of Minnesota suggests that it may be due to an effect on stress and the change in diet results in these horses becoming less ‘anxious’. However, trainers have in the past highlighted practical problems with this approach.

Some have reported that long-term palatability may be a problem with this type of diet, as horses seem to instinctively like the sweet, cereal rich coarse mixes and cubes, typical of traditional racing feeds. Measures that can be taken to avoid such problems include: 1. Identify problem horses as early as possible and adjust their ration to prevent them becoming accustomed to traditional racing feeds. 2. Feed 4 or 5 smaller meals per day rather than 3 larger ones. 3. Mixes are often more palatable than cubes 4. Some unmolassed sugar beet can improve palatability Most racing diets need supplementing with salt Electrolyte provision, including sodium, potassium, chloride, calcium and magnesium is an important dietary aspect to evaluate for all horses in the yard, not just those that tie up.

Racing diets generally meet and exceed the requirements of potassium and chloride, which are two of three the main electrolytes lost in sweat. The third, sodium, is in my experience never present in sufficient quantities in proprietary feeds for horses doing more than light work. This may be largely due to manufacturing constraints. However, sodium is easily supplemented by adding ordinary table salt daily to feeds (typically between 25-75g per day depending on work load). Whilst calcium and magnesium intake is usually adequate, the calcium to phosphorus ratio of the diet may not be optimal, especially if feeds are top dressed with oats.

It should also be recognised that, there exists quite marked differences between horses in their ability to absorb electrolytes and for this reason a creatinine clearance test can be useful in the further investigation of problem horses. This test (which involves taking paired blood and urine samples for analysis of the major electrolytes) helps the vet and nutritionist to take account of individual variation in electrolyte absorption and excretion and to modify the diet accordingly. Vitamin E intake can be low in some pre-training diets Vitamin E and selenium content of the diet should also be studied carefully. Racehorses that repeatedly tie up are not necessarily deficient in these two micronutrients, but may have a higher requirement due to increased free radical production. In my experience, selenium is usually present at appropriate levels in most racing rations, however the level of vitamin E provided can often be lacking.

A higher daily intake of 1600-2400iu per day for a typical horse in training has been recommended in the scientific press. The range in vitamin E content of racing feeds is quite wide, typically between 250iu to nearly 500iu per kilogram of feed. So a horse in full work may receive anything between 1500 to 3000iu per day, excluding forage and supplements. However, many trainers rely on the use of non-specialist low energy feeds during early training and these are obviously fed at a much lower level of intake compared to racing feeds for horses in full work. This could therefore result in vitamin E intake during this period being nearer to 1000iu per day. Poor hoof condition is a common gripe for trainers and farriers Poor hoof condition is another common problem that develops in early training and which can often deteriorate as training progresses.

Whilst there are many conformational and biomechanical factors that contribute to poor hoof condition in Thoroughbreds, nutrition is an area that should not be ignored. It is true to say that most of the relevant nutrients such as quality protein, calcium, zinc, methionine and fatty acids are supplied in a typical racing diet. However, the micronutrient that has received most attention in the scientific literature with respect to improving hoof horn quality is biotin. Biotin, a B-group vitamin, is generally provided at a level of intake in most racing feeds that easily meets a horse’s basal requirement. However, the daily intake reported to improve horn quality is typically 10-20 times higher than this.

Biotin has been reported to improve hoof horn quality when fed daily at levels between 10 and 20mg per day. Patience however, is required with biotin supplementation, as benefits are unlikely to become apparent for 6-9 months. But remember that biotin is worth feeding for 12 months of the year – as the horn grown in the early winter will be raced on in the spring and summer. Getting the basics right for respiratory health Development of respiratory disease during early training is also a commonly encountered problem. I always compare a yearling’s first venture into a training or pre training yard to a toddler starting nursery for the first time, which can often involve consecutive colds and associated bugs for the first year or more.

Indeed, the adaptive part the mammalian immune system is strengthened through exposure to different infectious challenges. It is not surprising therefore, that avoiding some form of respiratory disease during pre or early training is an uphill struggle. Numerous nutrients that may support the immune system have been investigated by scientists in man and other species, such as glutamine, antioxidants including vitamin C and E, probiotics, prebiotics, omega 3 fatty acids, adaptogenic herbs, whey protein and others.

The vitamin C level in the fluid surrounding the lungs is reportedly decreased in horses suffering with Recurrent Airway Obstruction and other types of airway inflammation (e.g. bacterial infection), and some vitamin C supplementation can be warranted where a problem is identified. Glutamine is a major fuel source for cells of the immune system and whilst the merits of supplementation in horses have not been proven, a fairly recent study indicated that horses infected with the equine influenza virus exhibited a significant decline in blood glutamine 41 days after exposure. There may well be other nutrients amongst those cited above that could prove useful, however there are few if any products (or ingredients) that have extensive and unequivocal scientific evidence to support claims that they ‘enhance or boost’ the equine immune system. Before turning to nutraceuticals for all the answers, some fundamentals can be addressed.

Good clean bedding is essential, as are well-ventilated stables and clean forage. Whilst American hay has a good reputation for being clean, with very low mould and yeast counts on analysis, many trainers prefer to use English hay for early training and some will use it through the season. Unfortunately, our variable climate means that producing consistently clean hay can be difficult. Whilst haylage is a viable alternative to hay, as the process of fermentation keeps the level of mould and yeast to a minimum, it is not infallible and haylage that has been produced badly, or which has become contaminated is a serious issue.

I would recommend that before committing to a batch of hay or haylage, some basic analysis of moulds and yeasts is money well spent to ensure that potential respiratory challenges from forage are minimised. Total mould and yeast analysis cfu/g from forage sampled from racing stables Total Moulds Total yeasts Thermophilic spores Hay – English Timothy 270 150,000 150,000 150,000 <10 Haylage – English Rye 10 <10 30 * No visible spoilage was seen in any of these forage samples Retention of calcium is reduced in early training Finally a discussion of the problems of pre and early training would not be complete without reference to bone. Many of the problems encountered at this time relate to changes in bone strength and density during training. When a racehorse enters training for the first time their cannon bones have been shown to go through an initial period of demineralisation, which reaches its greatest severity at about 60 days into training (US based study). Remineralisation then occurs as training progresses.

The initial demineralisation phase results partly as part of the remodelling process but also as a result of a change in the nature of the diet (less forage and more cereal), as the horse moves from stud to training or pre training yard. Current thinking follows that adequate calcium content in the diet is especially important during the initial demineralisation phase, as the horse’s ability to retain calcium in the body seems to be reduced. Attention to the calcium to phosphorus ratio of the diet is also vital, especially if top-dressing with cereals. The dietary magnesium content should also be evaluated in this respect as it is sometimes overlooked. Silicon supplementation shows some evidence of efficacy in reducing some injuries in racehorses but its powder form as sodium zeolite has limited its use. A liquid form is now available and although promising, as the intake per day is very low, it does not as yet have a scientifically proven track record.

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Nutritional Support for bone - maintaining a strong skeleton

Dr Catherine Dunnett (European Trainer - issue 16 - Winter 2006)

The expression ‘no foot no horse’ should perhaps be extended to cover all the bones of the skeleton, for as far as racehorses are concerned, without strength and durability in this area a trainer’s job is fraught with difficulties. The number of training days lost to lameness in a season is testament to this. A racehorse’s diet should help to maintain the skeletal system during rigorous training. This task is no doubt easier when the skeletal foundations have been firmly laid in utero and during the rapid growing phase.

The formation of cartilage and its subsequent conversion to bone ‘proper’ is one of the key processes to highlight. Long bones develop in the foetus from early bone templates that are composed entirely of cartilage. Conversion of cartilage to bone occurs initially within a central area of ossification (bone formation) within the long bones, known as the diaphysis and then also at each end of the bone (epiphysis). There are various abnormalities that can occur during the development of bones and joints that may involve problems during the localised conversion of cartilage to bone, or with bone lengthening, or changes within the bone after it has formed, once a horse has commenced training. Nutrition is only one of many factors involved in DOD Osteochondrosis (OCD) involves disruption to the normal conversion of cartilage to bone within the areas of ossification. For many years, researchers viewed nutrition as the key to OCD, however, it is now recognised that genetic predisposition, body size and mechanical stress, as well as trauma are all additional factors that must be considered.

Whilst diets that simply oversupply energy have been demonstrated to increase the incidence of OCD, the previously hypothesised causal link with excessive protein intake has not been proven. This suggests that the source of the energy in feed is an important issue. Recent research supports this, as it has been reported that diets with a high glycemic nature, i.e. those with a high starch and sugar content (typical of the more traditional stud and youngstock rations), appear to be more likely to trigger OCD. However, one would suspect that this would be more apparent in genetically susceptible animals. Many mineral imbalances in the diet have also been implicated as causative factors in OCD, but few have any strong evidence to support their role. For example, OCD lesions have been reproduced experimentally in foals maintained on a very high phosphorus intake.

This type of diet could arise inadvertently by feeding straight cereals such as oats, without a suitable balancer or complementary feed such as alfalfa to redress the low calcium to phosphorus ratio in the grain. Less extreme versions of this diet could occur through excessive top dressing of ‘balanced’ coarse mix or cubes with additional cereals such as oats or barley, as is common practice in many yards. A low copper intake, especially during the last trimester of pregnancy, has also been implicated in OCD. Copper has received particular focus due to its functional role in the activity of a key enzyme involved in formation of the collagen cross-links. However, other trace minerals including manganese and zinc may be equally important during this key stage in a foal’s development in utero, as they are necessary co-factors for important enzymes involved in regulating cartilage metabolism. Blood tests that challenge the premise that horses are unaffected by molybdenum levels in grazing In grazing youngsters, a secondary copper deficiency can be caused by excessive molybdenum levels in pasture. In cattle, bacteria in the rumen form complexes between molybdenum and sulphur.

These thiomolybdate complexes will bind copper within the gut and when absorbed will then search out further copper to bind, either circulating in the blood or in association with copper dependent enzymes. This can severely impair the activity of some key enzymes involved in growth processes and cartilage turnover. However, as a horses gut is somewhat different from a cow’s, in that the hindgut (the equivalent of the rumen) is positioned after the small intestine and not before, there is theoretically less opportunity for these thiomolybdates to be absorbed and ‘cause trouble’. At least this is what has been largely accepted from previous studies in horses that focussed on plasma copper levels and copper absorption. However, new blood tests that can be used to measure the activities of key copper dependent enzymes, such as superoxide dismutase (SOD), in conjunction with traditional measurements of plasma copper status and the presence of thiomolybdate complexes suggest that this may not always be the case.

Dr Stewart Telfer of Telsol Ltd, routinely carries out such tests in cattle and has to date analysed about 100 samples in horses suspected of having an issue with molybdenum interactions. He says, “From our work, it is clear that horses do suffer from molybdenum (thiomolybdate) toxicity. The interactions between copper, iron, molybdenum and sulphur will take place in the horse’s gut and in certain situations, not always linked to a high molybdenum intake, will result in the horse suffering from molybdenum (thiomolybdate) toxicity. Dr Telfer however, acknowledges that only relatively small numbers of samples in horses have been tested and the laboratory does not currently have a definitive reference range for horses. Calcium and phosphorus may be mobilized from bone to compensate for ‘acidic diets’ When yearlings first move into training yards, they usually experience a significant change in their diet that has consequences for bone metabolism during this period in their lives when some continued growth occurs and the skeletal system is put under considerable strain. In general terms, a ‘stud diet’ has what’s called a high dietary anion to cation ratio (DCAB).

This is largely due to the high inclusion of ingredients like soya and forages. A ‘full race training diet’ on the other hand tends to have a much lower DCAB (is more acidic) due to the reduction in forage intake and higher inclusion of cereals such as oats. The significance of a low DCAB is that it reduces the efficiency of calcium absorption and retention within the body and may contribute to the reduction in bone density seen in horses in early training. This surely is an argument for limiting the intake of cereals and maximising forage intake during the early stages of training when a high cereal intake is largely unnecessary. Calcium is the most abundant mineral in the horse's body, with the majority being present in the skeletal system. Phosphorus is also found in large amounts in bone in close association with calcium.

A racehorse’s diet should provide an adequate intake of both minerals but also needs to provide a balanced calcium to phosphorus ratio of near to 2:1. Although exercise demands a slight increase in calcium intake above the requirements for maintenance, this is usually satisfied by the generalised increase in feed intake. However, the efficiency with which individual horses absorb calcium varies and should certainly be investigated when a calcium-related issue arises. This can be achieved by examining an individual horse’s calcium and phosphorus status, by looking at the diet and also within the body using a creatinine clearance test. Topdressing – a national pastime When using straight feeds, or when topdressing ‘straights’ onto a ‘balanced’ racing mix or cubes, be aware that certain types of feed are much higher in calcium relative to phosphorus and vice versa (see table). Alfalfa, with its high calcium to phosphorus ratio, makes an ideal partner for cereals, which are low in calcium relative to phosphorus. Conversely, the traditional combination of oats and bran is not ideal, as it combines two feeds, which are low in calcium.

Remember that you can use a supplement or feed balancer to carefully correct any deficiencies or imbalances when feeding straights. Equally excessive addition of oats to a balanced mix or cube can decrease the calcium to phosphorus ratio sufficiently to cause problems. Most commercial mixes or cubes have sufficiently high calcium to phosphorus ratios to practically be able to withstand the addition of 1-2kg of oats daily, however any increase beyond this is unwise without further corrective measures. Feeds High in Calcium &Low in Phosphorus Feeds Low in Calcium & High Phosphorus Alfalfa Oats Sugar Beet Barley Seaweed Maize Wheat Bran Horses have a complex regulatory system, involving certain hormones, for ensuring that the proportion of calcium in the body, relative to that of phosphorus, remains stable and that the level of active or ‘ionised’ calcium in the blood remains within tight limits. If for one reason or another the level of calcium relative to phosphorus in the blood drops, a number of safety systems will be triggered to redress the balance. Bone acts as a reservoir of both calcium and phosphorus, which can be drawn on when necessary. The body's balance of calcium and phosphorus is continually 'corrected' by either conservation or loss of calcium or phosphorus in the urine, via the kidneys or through the skeletal system. Sustained calcium and phosphorus imbalance can, however, contribute to developmental orthopaedic diseases (DOD) in young horses, or lameness and sometimes bone fractures in mature horses. Research shows silicon is a trace mineral worth a second look.

Moving on to a less well-recognised trace mineral as far as bone is concerned, there has been some interesting research carried out into the effects of supplemental silicon in the racehorse’s diet. Silicon is a natural constituent of plants and provides structure and rigidity to some of their cell walls. It therefore forms a natural part of the horse’s diet, however, the availability in horse feed is apparently limited. Silicon plays a role in the development of new bone and is also important for the calcification process. It is therefore a relevant micronutrient for horses in training, as bone is dynamic and is constantly undergoing change, in response to forces placed upon it during the training process.

Research carried out by Dr Brian Nielsen at Michigan State University in the early nineties reported a dramatic decrease in injury rates in quarter horses fed a bioavaiable form of silicon as sodium zeolite A. This program of research has also established that the silicon is available to foals via the milk of supplemented mares. However, thus far the group have not uncovered the mechanism by which the beneficial effects of silicon are brought about. However, the form in which sodium zeolite A is fed (a chalk like powder) and the level of intake used in these studies (about 200g per day for a 500kg horse) makes it impractical to use as a feed supplement unless it can be incorporated within a feed pellet. In conclusion, attention to those factors within the diet that support bone turnover is likely to contribute to a reduction in injuries observed, however, the implementation of appropriate training techniques and use of suitable training surfaces also has a huge impact on the durability of horses in training in comparative terms.

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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 Racehorses… 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.

Ian Lane (European Trainer - issue 15 - Autumn 2006)

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.

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Electrolyte Balance – vital to the proper functioning of a racehorse's system

Catherine Dunnett (European Trainer - issue 14 - Summer 2006)

Electrolytes are essential components of the racehorse’s diet as they are vital to the proper functioning of the body’s basic physiological processes, such as nerve conduction, muscle contraction, fluid balance and skeletal integrity. The major electrolytes, sodium, potassium, chloride, calcium and magnesium are widely distributed within the body, but can be more concentrated in particular organs and tissues. For example, the level of potassium is very high in red blood cells but quite low in plasma, and the level of calcium in blood is low, but comparatively very high in bone and in muscle cells. The body has in-built mechanisms that work to maintain the correct electrolyte balance within the tissues, fluids and cells. These modify the absorption of electrolytes in the gut, or their excretion by the kidneys. These mechanisms are not foolproof however, and electrolyte loss through sweat can be a major issue for Thoroughbreds. The sweat of the equine athlete, unlike its human counterpart, is hypertonic; meaning that horse sweat contains higher levels of electrolytes than the circulating blood plasma. Consequently, the horse loses comparatively large quantities of electrolytes through sweating.

Although the electrolyte composition of equine sweat varies between individuals, on average a litre would contain about 3.5g of sodium, 6g of chloride, 1.2g of potassium and 0.1g of calcium. From this we can see that the majority of the electrolyte lost is in the form of sodium and chloride or ‘salt’. The amount of sweat produced on a daily basis and therefore the quantity of electrolytes lost differs from horse to horse and depends on a number of factors. As sweating is primarily a cooling mechanism, how hard a horse is working, i.e. the duration and intensity of exercise and both the temperature and humidity of the environment are all significant. Horses can easily produce 10 litres of sweat per hour when working hard in hot humid conditions. Stressful situations can also cause greatly increased sweating.

For example, during transport horses can lose a significant amount of electrolyte through sweating and the opportunity for replenishing this loss through the diet may be less as feeding frequency is reduced. Use of electrolyte supplements either in the form of powders or pastes is advocated before, during and after travel, especially over long distances. Jim Paltridge from IRT (UK) Ltd, (International Racehorse Transport), says, "we use a powdered electrolyte supplement added to the feed on a regular basis given for the 3 days prior to travel. We find this helps offset much of the loss normally incurred during transport and subsequently the horses arrive at their destination in better shape. We feel this electrolyte supplementation is a valuable attribute in the ongoing battle to reduce in-flight dehydration".

Electrolytes lost from the body in sweat must be replenished through the diet. All feeds, including forages, have a natural electrolyte content and in concentrate feeds this is usually enhanced by the addition of ‘salt’, which is sodium chloride. Forages such as grass, hay, haylage or alfalfa (lucerne) naturally contain a large amount of potassium, as can be seen from the table 1 below. In fact, 5kg of hay for example, would provide in the region of 75g of potassium, which largely meets the potassium needs of a horse in training. It is therefore questionable whether an electrolyte supplement needs to routinely contain very much potassium unless forage intake is low. Calcium is another important electrolyte, but it is lost in sweat in only very small amounts and its availability in the diet tends to be very good.

Calcium is particularly abundant in alfalfa with each kilogram of the forage providing nearly 1.5g of calcium. A kilo of alfalfa alone would therefore go a long way towards replacing the likely calcium loss through sweating. In addition, the calcium found in alfalfa is very ‘available’ to the horse in comparison to other sources, such as limestone. Calcium gluconate is another very available source of calcium, however, it has a relatively low calcium content compared to limestone (9% vs. 38%) and so much more needs to be fed to achieve an equivalent calcium intake. Interestingly, there is great variation between individual horses in their ability to absorb calcium, however, scientific studies carried out at Edinburgh Vet School showed that this variability was considerably less when a natural calcium source in the form of alfalfa was fed.

By far the most important electrolytes to add to the feed are sodium and chloride or ‘salt’. The levels of sodium and chloride found in forage are quite low and due to manufacturing constraints only limited amounts of salt can be added to traditional racing feeds. A typical Racehorse Cube fed at a daily intake of 5kg (11lbs) would provide only about 20g of sodium and 30g of chloride. As can be seen from table 2 this is a fair way short of meeting the daily requirements for these particular electrolytes by a racehorse in hard work.

It is therefore very important that supplemental sodium and chloride is fed. Ordinary table salt is by far the simplest and most economical electrolyte supplement, but the downside is the issue of palatability as the addition of larger quantities of salt to the daily feed can cause problems with horses ‘eating up’. As an alternative salt could be added to the water, but only when a choice of water with and without salt is offered. Salt should not be added to the water if it puts a horse off from drinking, as dehydration will become a problem.

Inadequate water intake can also contribute to impaction colic. Saltlicks are another alternative, although intake can be vary variable and we rely on the horse’s innate ability to realise its own salt requirements, which is questionable. So addition to the feed is by far the best route for adding salt or electrolyte supplements to the diet. Splitting the daily intake between two or three feeds can reduce problems with palatability.

Mixing salt and Lo Salt can make another simple DIY electrolyte supplement in the proportion of for example 500g to 250g respectively. Salt is sodium chloride (NaCl), whilst Lo Salt contains a mixture of sodium chloride and potassium chloride (KCl). This formulation provides 3g of sodium, 6g of chloride and 1g of potassium per 10g measure. This DIY mixture will replace these electrolytes in the approximate proportions that they are lost in sweat. What are the implications of a racehorse’s diet containing too little or too much of an electrolyte and how can we assess this? An inadequate level of certain electrolytes in the diet in some horses may simply result in reduced performance. In other individuals, it can make them more susceptible to conditions such as rhabdomyolysis (tying up), or synchronous diaphragmatic flutter (thumps), both of which are regularly seen in horses in training. Conversely, an excess electrolyte intake is efficiently dealt with by the kidneys and is ultimately removed from the body via the urine.

Therefore, the most obvious effect of an excessive electrolyte intake is increased drinking and urination. For this reason, the use of water buckets rather than automatic drinkers is preferred, as whilst the latter are far more labour efficient, the ability to assess water intake daily is lost. Excessive electrolyte intake can also be a causative factor in diarrhoea and some forms of colic. There is also some recent evidence in the scientific press that suggests that repeated electrolyte supplementation might aggravate gastric ulcers. However, these early studies used an electrolyte administration protocol typical of that seen during endurance racing, rather than simply a daily or twice daily administration, which is more commonly used in racing.

Supplements that contain forms of electrolyte that dissolve more slowly in the stomach, however, may be less aggressive to the sensitive mucosa. Unfortunately blood levels of sodium, potassium, chloride or calcium are poor indicators of whether dietary intake is sufficient or excessive unless it is very severe. This is because the body has effective systems for regulating the levels of these electrolytes in blood within very tight physiological limits. A creatinine clearance test, which measures the electrolyte content of a paired blood and urine sample is a much more useful indicator of dietary electrolyte adequacy.

There are a large number of commercial electrolyte products available, with a wide range in the breadth of ingredients that they contain. Consequently, they vary enormously in the amount of electrolyte that they deliver per recommended daily dose, as can be seen in table 3. In addition, whilst some glucose or other carbohydrate can help improve palatability, its presence should not compromise the amount of electrolyte that is contained within the supplement. In humans, it is recognised that the uptake of sodium from the gut is improved in the presence of glucose, while this effect in horses has not been firmly established. Electrolyte paste products are also often used either before and or after racing or travel.

These products are useful as they allow rapid electrolyte intake even when feed eaten may be reduced following racing. These electrolyte pastes often provide a more concentrated form of supplement and it is extremely important to ensure that the horse has access to water immediately following their use. Failure to do this may mean that the concentration of electrolytes in the gut actually draws water from the circulating blood, which can exacerbate dehydration. Another disadvantage with paste supplements is that if they are not formulated well, with an appropriate consistency, they can be difficult to dispense from a syringe and the horse may also be able to spit most of the product out after administration.

Some simple rules of thumb for choosing a good electrolyte are that salt should be one of the first ingredients listed on pack, as all ingredients are listed in descending order of inclusion. Additionally, be wary of supplements that taste sweet, as they may contain a lot of carbohydrate filler and little electrolyte. Some electrolyte supplements also contain many superfluous ingredients such as vitamins and trace minerals. The inclusion of these latter ingredients is largely unwarranted and their presence could cause issues with oversupply if the electrolyte is multi-dosed daily. Some electrolyte products specifically marketed towards racing may also contain bicarbonate.

The theory behind its inclusion is sound as ‘milk shaking’, whilst outside the rules of racing, has some scientific validity. However, the limited amount of bicarbonate contained in such electrolyte supplements is unlikely to have the positive effect on performance attributed to the former practice. Other extra ingredients such as pre-biotics may be more useful as they may improve the absorption of some electrolytes. In Summary, electrolyte supplementation in one form or another is essential within a racing diet. Ensuring that you are using a good electrolyte supplement is important and the quantities fed must be flexible and respond to changes in the level of work, degree of sweating and climate.

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The role of protein in the racehorse's diet

Dr Catherine Dunnett (European Trainer - issue 13 - Spring 2006)

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.

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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.

Sue McMullen (European Trainer - issue 7 - Spring 2007)

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.