How the digestion of nutrients may improve horses’ overall condition

By John Hunter

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

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

Beetroot juice supplementation

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

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

Vitamin B12

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

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

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

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

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

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

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

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THIS ARTICLE FIRST APPEARED IN - EUROPEAN TRAINER - ISSUE 40

To beet or not to beet? - Will beetroot become part of the racehorse’s diet?

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Digestive Aids - what is available to racehorses?

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(European Trainer - issue 26 - Summer 2009)

Amino Acid Supplements - the important element of protein

Horses in training are traditionally fed a diet that is high in protein, but it is the amino acid content of the protein-rich ingredients that is the important component.

Dr Catherine Dunnett (European Trainer - issue 24 - Winter 2008)

The role vitamins play in the diet of a racehorse

Vitamins are a key part of the diet for racehorses and although the clinical signs associated with an overt deficiency or excess of one vitamin or another are rare, we should not presume that the level of vitamins provided in the diet is optimised for performance.

Catherine Dunnett (Trainer Magazine - issue 23 - Autumn 2008)

Oiling the Wheels - using oil as a supplement in the diet of racehorses

Historically, oil has not featured highly in the diets of horses in training, or indeed those of other horses. The natural oil content of pasture and other forages is quite low at between 2-3% on a dry matter basis, yet despite this, horses digest oil extremely well. Oil added to the racehorses’ diet is tolerated well, with no major palatability problems having been reported. There are many advantages to feeding an oil supplemented diet to horses in training. For feed manufacturers, the addition of increasing amounts of oil in a feed formulation allows the addition of energy or ‘calories,’ without any contribution towards the starch and protein content of the feed.

This means that lower starch feeds can be produced, whilst maintaining the total energy content of the feed. This type of diet can help prevent the digestive system from being overwhelmed by the presence of starch in the diet. Additionally, beneficial effects of this type of diet on behaviour have also been reported and horses that are prone to tying up may also gain. Oil supplementation can also potentially bring other beneficial effects e.g. on coat condition and on respiratory health or mobility and performance. However these additional desirable effects are likely to depend not only on the quantity of oil within the daily ration, but also on the nature of the oil included.

OIL - MORE ENERGY THAN MOST INGREDIENTS IN FEED

The energy or calorie content of oil is higher than any other ingredient commonly used in the manufacture of racing feeds, as seen from the Table 1 below. In a direct comparison with oats, vegetable oil such as corn oil provides about 70% more energy for a given weight. From a trainer’s perspective, top dressing oil onto an existing ration allows an increase in the energy density of the feed i.e. more calories for the same volume of feed. This is particularly useful for fussy feeders helping to keep their meal sizes relatively small. Ingredient Energy (MJ/kg) Corn Oil 38 Oats 12.5 Racing Mix 13 Hay 7.5

Table 1 - Estimated energy content of different components of a racing diet. Oil is usually added into the diet in oz or ml rather than in kilograms. So for a more practical comparison, a coffee mug of oil, which is equivalent to about 250ml (225g), would provide about 9 MJ of energy, which is equivalent to about ¾ of a flat scoop of oats (750g). There are many types of oil besides corn and soya that have been fed to horses over the years. Vegetable oils derived from rapeseed or canola, sunflower, safflower, coconut and even peanut have been previously fed. Fish oils such as tuna oil, salmon oil and cod liver oil have also been used. Cod liver oil should, however, be used sparingly due to the high fat soluble vitamin content.

Other high oil containing ingredients that are commonly used in racing feeds, or in some cases to top-dress racing diets, include rice bran, linseed meal, full fat soya and naked oats (see Table 2). Whilst the oil content of all of these ingredients is relatively high, the starch content varies quite significantly. In terms of oil delivery and starch content, linseed meal would clearly be a good choice for oil supplementation where a low starch containing diet was desired. Ingredient % Oil Content % Starch Content Ricebran 16-20 15-27 Linseed Meal 37 5.5 Full Fat Soya 20 4.5 Naked Oats 10 53 Table 2 - Percentage oil and starch content of typical components of a racing ration * Information taken either from actual analysis or from Premier Atlas Ingredients Matrix

EFFECTS ON BEHAVIOUR

There has been some suggestion in the scientific literature in recent years that feeding a ration that is high in oil and fibre and low in starch can have a beneficial effect on behaviour, in terms of reducing excitability. Studies on Thoroughbreds with recurrent exertional rhabdomyolysis (RER) reported decreased excitability and nervousness, as well as lower resting heart rates, when they were fed a low starch high oil containing diet, compared with an isocaloric diet that was low in oil and high in starch. This effect, however, is likely to have been mostly due to the reduction in starch intake from cereal, rather than the oil content per se. The use of increased amounts of oil in the diet does, however, facilitate the reduction in starch content without leaving an ‘energy gap.’

BENEFICIAL PROPERTIES FOR TYING UP

More recently, stress has been implicated as a trigger for RER in susceptible horses and so the potentially beneficial effects of oil supplemented diets that are also low in starch and high in fibre have been extolled. Accordingly, lower plasma concentrations of creatine kinase (CK) following a standard exercise test have been reported in response to such diets, in comparison to traditional racing type diets that are high in starch and low in fibre and oil. Specialists on RER have successfully advocated the use of such diets for horses in training that are at risk from RER. In addition, there is a strong argument for the use of such diets during pre-training and the early part of actual training. Significant oil supplementation during full training, if the starch content of the diet is also drastically reduced, is more controversial due to the metabolic effects that can be induced and so the potential effect on subsequent exercise performance.

METABOLIC EFFECTS OF OIL SUPPLEMENTATION

Putting this section into context, the metabolic adaptations to oil supplementation have been reported to occur when relatively large quantities of oil are fed, typically where near to 20% of the total dietary energy intake is provided by oil. For a cube or a mix fed at, for example 6kg per day, this would require a 10% declaration of oil for that feed. For comparison most racing feeds would contain oil at the level of inclusion of 5 - 8.5%.

A high level of oil supplementation has been reported latterly to decrease resting muscle glycogen concentration and improve the use of fat as a fuel source during low and moderate intensity exercise (trotting through to slow cantering) through metabolic adaptation at the muscle level. This offers the possibility of sparing muscle glycogen stores during low intensity exercise training, but equally may impede muscle glycogen replenishment following hard work or racing, which may disadvantage (see European Trainer Issue 19 Racing Power - Supporting Muscular Effort through Nutrition). The effect of oil supplementation on high intensity exercise performance such as racing is very controversial. Some studies show little or no effect, whilst others have shown a beneficial effect. As a result the scientific community are divided and so the jury is still very much out in this respect.

OTHER HEALTH BENEFITS OF OIL SUPPLEMENTATION

Dietary oil also provides a source of what are termed essential fatty acids, namely linoleic acid, which belongs to the omega 6 family of fatty acids and α-linolenic acid, which belongs to the rival family the omega 3’s. Most ingredients found in a racehorses’ diet are rich in the omega 6 type of fatty acid with much less omega 3 fatty acid present. The role for dietary omega-3 fatty acids which has been proposed in maintaining joint and skin health, and in supporting immune function, fertility and respiratory health, makes them an attractive nutraceutical ingredient for racehorses. The use of linseed meal has recently increased in proprietary horse feed and supplements. However, although α-linolenic acid is a precursor of the longer chain more bioactive omega 3’s, eicosapentanoic acid (EPA) and docosahexanoic acid (DHA), the efficiency of conversion is quite low.

Therefore nutraceutical ingredients that provide a more concentrated source of either or both EPA and DHA are becoming more widely used. Ingredients such as micro-encapsulated and deodorised fish oils e.g. tuna oil, as well as green lipped mussel, and more recently plant sources of DHA in the form of algae are now more commonly seen in equine products, primarily supplements. Few studies into the efficacy of omega-3 fatty acids have, however, been published in horses. In a preliminary study using ponies with sweet itch, a beneficial effect of linseed on inflammatory skin conditions was proposed. Encouraging results have also been reported for the effect of supplementation with a combination of EPA and DHA on arthritic horses. In humans there is some evidence to support a protective role for omega-3 fatty acids in human asthma, a condition that is not unlike recurrent airway obstruction (RAO) in horses, but the results are not indisputable. A recent supplementation study with omega 3 fatty acids in horses, however, did not significantly alter clinical indicators of pulmonary function, although the leukocyte counts in epithelial lung lining fluid were reduced in the omega-3 supplemented horses. This may suggest an effect of supplementation on pulmonary inflammation.

HOW MUCH IS ENOUGH AND CAN THERE BE TOO MUCH?

The answer to this question is not straightforward as if you are intending to top dress oil onto feeds, the quantity required will largely depend on how much is present in the basal diet already. Certainly, where the oil is being used to increase the energy density of the diet and reduce the inclusion of starch rich ingredients, a level of 250-300ml per day to replace a kilo of oats or other racing feed would not be inappropriate, where the basal diet contained a low level of oil. For horses that struggle to maintain condition, addition of 100-150mls of oil daily into the existing ration is likely to help. One should always remember, however, that oil does not provide any protein or vitamins and minerals and so must be fed in conjunction with a balanced diet, particularly with respect to antioxidant vitamins such as vitamin E. Oil should always be introduced to the diet slowly and the daily amount spread over several meals. In addition, any adverse affect on dropping consistency may be a warning that the level of oil in the total diet is too high and the level should be reduced. As far as the neutraceutical omega 3 fatty acids are concerned, we know much less about the quantities required, but hopefully research will continue in this area to investigate their potentially beneficial effects.

Racing power - supporting muscular effort through nutrition

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.

Nutritional ergogenic aids for horses

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?

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.

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

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

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

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

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

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

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

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

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

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

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

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

The role of protein in the racehorse's diet

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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