The Role Vitamins Play in the Diet
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 optimized for performance. Horses are, generally speaking, quite tolerant of sub-clinical deficiency or excess with regards to vitamins, and the margin of acceptable intake to prevent health issues is therefore relatively wide in most cases. However, maintenance of health is a separate issue compared to optimal performance, which is the ultimate target for horses in training.
Catherine Dunnett (14 October 2008 - Issue Number: 10)
Feed contaminants - how big a risk are they?
or all professionals associated with the training and competition of horses under the rules and regulations of racing, the choice of which feed products to use has never been greater, and the range appears to grow on a daily basis. This is especially true of the plethora of dietary supplements (otherwise known officially as complementary feeds) available.
Dr Catherine Dunnett and Dr Mark Dunnett (10 July 2008)
By Dr Catherine Dunnett and Dr Mark Dunnett
For all professionals associated with the training and competition of horses under the rules and regulations of racing, the choice of which feed products to use has never been greater, and the range appears to grow on a daily basis. This is especially true of the plethora of dietary supplements (otherwise known officially as complementary feeds) available.
Feeds and other contemporary nutritional supplements are not pure products in the same manner that veterinary pharmaceuticals are and thus they will, in a traditional sense, contain foreign substances, even though this is commonly only at trace levels that will have no discernible effect on the horse. Numerous harmful or undesirable substances can potentially contaminate the equine diet, whether manufactured feeds and supplements, or grazing and preserved forages.
These dietary contaminants can be divided into groups including heavy metals, non-metallic toxic elements, pesticides, mycotoxins, plant toxins, and pharmacologically/physiologically active substances that are considered prohibited or foreign substances within the horse under racing rules and regulations. There is some crossover between plant toxins and prohibited substances, but it is the latter category that concerns us within this article. Prohibited (foreign) substances Under the framework of the International Federation of Horseracing Authority's International Agreement on Breeding, Racing and Wagering, Article 6, a prohibited substance is described as - "…substances capable of giving a horse an advantage or being disadvantaged in a race, contrary to the horse's inherent merits." Article 6 further defines prohibited substances as- "
Substances capable at any time of acting on one or more of the following mammalian body systems:
• the nervous system
• the cardiovascular system
• the respiratory system
• the digestive system
• the urinary system
• the reproductive system
• the musculoskeletal system
• the blood system
• the immune system, except for licensed vaccines against infectious agents
• the endocrine system
• Endocrine secretions and their synthetic counterparts
• Masking agents
In broad and simple terms, a prohibited substance can be described as any substance (usually but not exclusively drugs/medicines) that has been given to a horse in its feed, or by any other means, that can exert an effect upon the horse. Certain factors make the presence of prohibited substances as contaminants in the production of equine feedstuffs almost inevitable.
Analytical techniques employed are increasingly sophisticated and sensitive and this latter fact serves to increase the likelihood of the detection of contaminants at levels that have been historically unattainable. Furthermore, the increasing diversity of dietary supplements leads to the introduction of unusual components into the equine diet. This is particularly the case with products that contain herbs or plant derivatives or extracts.
Additionally, there is increased sourcing of feedstuff raw materials from previously unaccessed regions of the world where quality control measures may be below the desirable standard and where novel crop infesting plants may be found. Contamination in compounded equine feeds and raw materials is varied, but the major sources can be categorized as follows:
Endogenous, natural feed constituents
Salicylates, DMSO Ubiquitous environmental contaminants
Arsenic Transport contamination of raw materials Caffeine, theobromine Manufacturing cross-contamination
Antibiotics Crop contamination by invasive plants
Morphine, atropine Racing yard feed contamination
Veterinary medication
The most commonly encountered prohibited substances in equine feedstuffs include salicylates, dimethylsulphoxide (DMSO), caffeine and theobromine, morphine, hyoscine, atropine and hordenine. There are however, a considerable number of pharmacologically active compounds potentially present in manufactured feeds, grazing and preserved forages that will be viewed as prohibited substances. Examples of these are listed in the table below, however the list is indicative rather than exhaustive. Prohibited substances potentially present in feedstuffs and grazing:
Prohibited substance
Feedstuff
Salicylic acid Alfalfa (Lucerne), willow Dimethylsulphoxide (DMSO) Alfalfa, others Caffeine Coffee Theobromine Cocoa Theophylline Coffee, Cocoa Morphine Poppy Codeine Poppy Hordenine Germinating barley, Phalaris grasses Hyoscine Belladonna plant species Atropine Belladonna plant species Lupanine Lupin seed Bufotenine Phalaris grasses Valerenic acid Valerian Dicoumarol Spoiled sweet clover Borneol Carrots, wood shavings Camphor Rosemary Unlike in the US, in Europe it is common practice for feeds and supplements to be tested by their manufacturers for potential contamination with prohibited substances before being released for sale. This practice is particularly evident for those products marketed to the performance sector. Typically, the service offered by laboratories such as HFL Ltd in the UK and the Laboratoire Des Courses Hippique (LCH) in France screens for the presence of commonly recognized feed contaminants which includes: Contaminant ARCI Classification† Morphine UK/France 1 Hyoscine UK/France 3 Atropine UK/France 3 Hordenine UK/France Not stated* Caffeine UK/France 2 Theobromine UK/France 4 Theophylline France 3 Bufotenine France Not classified/not actioned Methylbufotenine France Not stated* Dimethyltryptamine France Not stated* ? ARCI classification defines the regarded severity of a positive post-race test with these contaminants which will affect the severity imposed, with class 1 being the most severe.*Presumably, these would be regarded as being akin with bufotenine as they can all be associated with Phalaris grasses. Such pre-sales laboratory analysis is not common for US feed manufacturers.
To some extent this may reflect a reduced risk of contamination of feed with naturally occurring contaminants such as these above, due to less importation and transportation of raw materials. Natural feed constituents Salicylates and dimethylsulphoxide (DMSO) are present in numerous feed ingredients and pasture species. Salicylates are particularly abundant in grazing and forage legumes, such as clover and alfalfa respectively, and in willow-containing herbal supplements.
Plant salicylates are metabolized in the body to salicylic acid, a mild pain killer (analgesic) and anti-inflammatory. Salicylic acid is a metabolite of Aspirin. DMSO occurs at high levels in alfalfa and is also a weak analgesic and anti-inflammatory. DMSO can be used to enable other drugs to penetrate the skin. Owing to their widespread occurrence and pharmacological properties, international racing jurisdictions have established thresholds for their presence in post-competition urine and blood samples. In itself it is unlikely that feed-related salicylate load will cause testing thresholds to be exceeded and feed products are not tested to identify the presence of these substances.
Hordenine and bufotenine are recognized as occasional contaminants of equine feedstuffs. Both substances are constituents in Phalaris grass species (Reed Canary grass), and hordenine also occurs in germinating barley and other cereal grains.
Hordenine and bufotenine affect the central nervous system (CNS) of horses and are thus are regarded as prohibited substances under racing rules. They have both been detected in post-race urine samples across the US, Europe and Australia Feed crop contaminants Morphine and codeine present a less common but significant feed contamination issue. Their presence in post-race samples is a breach of prohibited substance rules as they can exert a significant stimulatory effect in the CNS of horses even at low doses.
During the last decade post-race urine samples have tested positive for opiates in the US, Australia, the UK and Ireland. Whilst the route of contamination has not always been established, feed contamination with material from opium poppies (Papaver somniferum ssp. somniferum), wild poppies (P. somniferum ssp setigerum) or ornamental poppies (P. Orientale) is likely due to the use of contaminated raw materials. The alkaloids hyoscine (scopolamine) and atropine are also known contaminants of horse feed that derive from contamination of growing cereal crops by Solanaceous plants including Deadly Nightshade, Henbane and Jimson Weed. Deadly Nightshade (Atropa belladonna) contains predominantly atropine, whereas Henbane (Hyoscyamous niger) contains primarily hyoscine. Owing to their potent pharmacological effects within the central nervous system and cardiovascular system, the presence of hyoscine or atropine in post-competition urine samples is regarded as a breach of the rules relating to prohibited substances.
Manufacturing and shipping contamination
Caffeine and theobromine are recognized contaminants of feeds and numerous instances of feed contamination and post-race positives occurred globally during the 1980s and 1990s. In the past, cocoa husk was used as a bulking agent in feed manufacture however, more recently its presence in feeds is believed to have arisen from contamination from other feed residues, such as biscuit meal or from contamination of raw materials, usually grains, during transport.
We are all aware of caffeine as a constituent of coffee and tea, whereas its chemically similar cousin theobromine is found naturally in tea and cocoa (chocolate). When ingested, both substances can act as stimulants to the heart, lungs and brain, and may also exert some degree of diuretic action (increased urination). As a consequence of the prevalence of caffeine and theobromine in the feed production chain and the difficulty in removing them, racing's regulatory authorities worldwide have largely implemented a threshold for theobromine in post-race urine samples. In the recent past in the US mepyramine, an antihistamine, has been identified in post-race samples and its appearance on these occasions was attributed to contaminated vitamin preparations.
Procaine, a local anaesthetic, has also been implicated in post-race positives on a number of occasions where on further investigation the source was discovered to be horse feed cross-contaminated at the mill with pig feed containing the antibiotic procaine penicillin. Environmental contamination Arsenic is a prohibited substance under equine competition rules, but as it is a ubiquitous environmental substance, a threshold level has been established for its presence in post-competition samples.
Additionally, arsenic levels in the racing environment can be increased by contamination from the use of pesticidal arsenic compounds, the most commonly encountered being wood preservatives used to treat construction timber and fencing materials. Cross-contamination Many veterinary drugs used therapeutically in a racing environment are formulated as powders so they can be administered mixed in with normal feeds.
Although this is a convenient method in contrast to a reliance on injections for example, it can present a significant risk of dietary contamination to horses other than the animal under treatment if shared feeding equipment is not kept scrupulously clean. Dusts from some drug formulations can contaminate and linger on surfaces in feed rooms, mangers or stables.
Certain drug formulations including isoxsuprine, clenbuterol and flunixin, can present a particular problem in this regard. Dietary supplements Racing is first and foremost a business, with the end-point being to maximize race wins and prize money and hence hopefully to increase future income from training fees. It is consequently understandable that any legitimate dietary approach which might benefit race performance and training capacity, or reduce the incidence of illness and injury, and accelerate recovery both from racing and ill health, might at the very least be evaluated.
This search for an ‘edge' is common to business and sport. Indeed, the perceived beneficial effects of dietary supplements in human sports have been to some extent translated to equine sports including racing. The increased availability of dietary supplements for horses can often be supported by sophisticated technical marketing and detailed scientific research.
But, whatever the motivation for the use of such products might be, whether backed by rigorous evidence of efficacy or not, the reality is that complementary feedstuffs are also potentially at risk of contamination. Although there has been no comprehensive survey of contamination in equine feed supplements, three such surveys have been conducted on human sports supplements, the results of which indicated that up to 20% of supplements tested contained prohibited substances (under IOC rules), principally anabolic steroids including nandrolone and testosterone.
As the levels of contaminants found were generally low and variable it was assumed that their presence arose through poor manufacturing practice on the part of the manufacturer or the ingredient supplier(s). Undeclared stimulants, such as caffeine and ephedrine, have also been identified in human sports supplements and these findings suggest deliberate adulteration to improve efficacy.
A recent doping case suggests that equine supplement contamination may become an issue for the feed and supplement industry and regulatory authorities, but on this occasion this post-race positive for the presence of the anabolic nandrolone seems to have arisen through the use of a human sports supplement in the horse, rather than a contaminated equine product. The use of dietary supplements in racing is becoming commonplace.
Products containing herbal or other plant based or nutraceutical ingredients are increasingly popular, possibly through a belief that these are not drugs and thus do not infringe the rules relating to prohibited substances. A useful example here would be products containing Devil's Claw powder or extracts. Devil's Claw is a plant related to Sesame and is native to southern Africa. It has recognized pain-relieving and anti-inflammatory properties in people and has been offered as an alternative to established over-the-counter pain relief medicines, such as Aspirin, paracetamol and ibuprofen, for many years, and is currently undergoing clinical trials.
Widespread promotion of Devil's Claw, as an herbal alternative to phenylbutazone for horses, began at a time when the continued approval for the use of this veterinary pain-relieving drug was in doubt. It is worth pointing out that the French racing laboratory, Laboratoire Des Courses Hippiques, have recently published methods for the detection of harpagosides, the active components in Devil's Claw, in equine post-race samples, and thus is it reasonable to assume that US regulatory laboratories may be screening for these substances.
The irony here is that, when viewed within the strictures of the rules and regulations of racing, if a supplement, or more accurately one or more of its constituents, has efficacy, by extrapolation it must affect one of the horses' body systems and is therefore prohibited, whether or not the laboratory is able to test for it. Trainer protection We should not be complacent on this issue and it would be prudent for trainers, wherever practical, to retain representative samples of all batches of feeds and supplements that they use, indeed the regulatory authorities proffer just such advice. This is certainly a worthwhile exercise, as in the event of a failed post-race test a defense of feed contamination will be strengthened by such physical evidence, which can be subjected to analytical scrutiny.
In practice, a successful demonstration of contaminated feed or supplement will not exonerate the horse's connections from a regulatory offense, but may well be a persuasive argument in mitigation concerning subsequent sanctions. In addition, being fully aware of the ingredients within feeds or supplements and of the nature and extent of any pre-sale quality assurance analysis by a manufacturer for the common contaminants (prohibited substances) should afford trainers some further protection and allow them to make informed purchases.
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.
Dr Catherine Dunnett (14 February 2008 - Issue Number: 7)
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.
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
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.
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
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.
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.
Dr Catherine Dunnett (European Trainer - issue 20 - Winter 2007)
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.
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.
Nutritional Ergogenic aids for horses - boosting performance
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.
Dr Catherine Dunnett (01 July 2007 - Issue Number: 4)
By Dr Catherine Dunnett
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.
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
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 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
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.
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)
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.
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.