Tying up some loose ends on rhabdomyolysis
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Catherine Dunnett (14 April 2010 - Issue Number: 16)
Economics of Feeding Horses in Training
While economic efficiency within any business is important to maintain profitability, there has been a particular focus on cost saving recently within the racing industry as a result of the underlying economic climate.
Catherine Dunnett
(05 February 2010 - Issue Number: 15)
Economics of Feeding Horses in Training
While economic efficiency within any business is important to maintain profitability, there has been a particular focus on cost saving recently within the racing industry as a result of the underlying economic climate.
Feeding is an area where economies can be made, but for the best effect any cost savings should not compromise the quality of the ration to the detriment of health or performance. Equally however, we should not shy away from a critical evaluation of our feeding management on a regular basis, especially if there is an element of sticking to the same way of feeding just because 'it's always been done like that'.
Catherine Dunnett (European Trainer - issue 28 - Winter 2009)
Will hemp change the way we feed horses?
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Dr Catherine Dunnett (14 October 2009 - Issue Number: 14)
Hemp for horses
Hemp has been synonymous with horse bedding for many years, as its fibrous properties give these products good cushioning and absorptive properties. Latterly, hemp has become popular as a food ingredient for people, being associated with well-known brands such as ‘The Food Doctor’ and ‘Ryvita’. It has also been investigated as a feed ingredient for farm animals including laying hens and dairy cows.
Hemp is primarily an oilseed crop like soya, linseed and rapeseed and it is the grain or seed that contains the majority of nutritional value. In comparison to other oilseed crops, hemp produces a very high yield and therefore it is not surprising that in recent years it has become a good economic crop for farmers in some parts of the world.
Catherine Dunnett (European Trainer - issue 27 - Autumn 2009)
Digestive Aids - what is available to racehorses?
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Dr Catherine Dunnett (16 July 2009 - Issue Number: 13)
Amino Acid Supplements - the important element of protein
Dr Catherine Dunnett (20 January 2009 - Issue Number: 11)
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)
Picky Eaters - a common problem in horses in training
Poor appetite in horses in training is not uncommon, whether this is a transient problem following racing, or, more regularly, during training in particular horses.
Dr Catherine Dunnett (European Trainer - issue 24 - Winter 2008)
Picky Eaters - a common problem in horses in training
Poor appetite in horses in training is not uncommon, whether this is a transient problem following racing, or, more regularly, during training in particular horses. In some situations, ‘failure to clean up’ may simply be explained by horses being offered more feed than they require and so they are being overfed, whilst in other instances, where it is accompanied with poor condition, the causes may be more complicated. Certainly, physiological mechanisms exist in horses to match energy and nutrient intake to daily requirements and these systems form the basis for self regulation of feed intake in horses in the wild or at grass.
Catherine Dunnett (14 October 2008 - Issue Number: 10)
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)
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.
KER Nutrition Conference - management of gastrointestinal and metabolic diseases
Kentucky Equine Research (KER) has maintained a prominent international presence in the nutrition research community for the past 20 years. Research trials have been conducted at the company’s research farm since the late 1980s, and results of this research have been published in numerous peer-reviewed journals and proceedings of scientific conferences.
Mark Llewellyn (European Trainer - issue 22 - Summer 2008)
Kentucky Equine Research (KER) has maintained a prominent international presence in the nutrition research community for the past 20 years. Research trials have been conducted at the company’s research farm since the late 1980s, and results of this research have been published in numerous peer-reviewed journals and proceedings of scientific conferences.
More importantly, findings from these studies have been put to use in the formulation of feeds for KER’s global network of feed manufacturers. The KER Nutrition Conference, held on the 16th and 17th of April in Lexington, Kentucky was attended by 130 guests, including feed manufacturers, sales representatives, veterinarians, nutritionists, and academics from 16 countries.
This year’s conference focused on the management of gastrointestinal and metabolic diseases. Founder and President Dr. Joe Pagan began by introducing Dr. Larry Lawrence, senior nutritionist at KER, who presented an in-depth review of the development of the gastrointestinal system. Dr. Lawrence addressed the changes that occur as a foetus grows within the womb and as the foal matures and begins to digest a diet of forages and concentrates.
A thorough explanation of the physical, enzymatic, and fermentative changes that occur to the gastrointestinal tract during gestation and growth gave conference attendees a better understanding of the importance of proper feeding. Colic, the most pervasive disease of the gastrointestinal tract in horses, was the next topic of discussion.
Dr. Nathaniel White, the Jean Ellen Shehan Professor and Director at Virginia Tech’s Marion duPont Scott Equine Medical Center and a world-renowned expert on equine gastrointestinal disorders, reviewed the prevalence of colic in today’s equine population.
He mentioned several risk factors: breed and gender predilection, dietary management, and other environmental and management practices. Additional risk factors such as previous colic episodes, parasitism, cribbing, gestation, transport, and anesthesia were touched on as well. In addition, he chronicled measures to prevent the syndrome. In a related lecture given later in the day, Dr. White addressed standard treatment protocols for colic including decompression of the stomach or intestine, use of systemic analgesics, strategies to promote gut motility and hydration, and treatment of impactions.
He then discussed proper nutrition of the horse after an episode of colic. A review of enteral (traditional) and parenteral (intravenous) nutrition followed. The speaker noted that although enteral nutrition is preferred, parenteral nutrition can provide long-term nutritional support, and stated that horses have been kept on complete parenteral nutrition for up to a month and have been able to maintain or gain weight. Dr. Frank Andrews, section chief of the department of large animal clinical sciences at the University of Tennessee College of Veterinary Medicine, spoke about the diagnosis and treatment of gastric and colonic ulcers in horses.
Gastric ulcers have been studied for several years and their prevalence among horses is well documented. Though colonic ulcers occur less frequently than gastric ulcers, Dr. Andrews listed several nonspecific signs including mild intermittent or recurring colic, lethargy, and partial anorexia that may hint at a problem.
As the problem worsens, so do the signs with complete anorexia, fever, diarrhoea and associated dehydration, and weight loss is common. Dr. Peter Huntington, the director of nutrition for KER’s Australasian branch, spoke to conference attendees about recent advances in laminitis research.
Despite the fact that a complete understanding of laminitis and its complex pathophysiologic processes remains elusive, laminitis seems to occur as a consequence of inflammatory, vascular, and enzymatic interactions. Dr. Huntington explained that a trend in laminitis research involves interest in metabolic or endocrine events that lead to laminitis. In regard to prevention, Huntington pointed out that genetic research could identify at-risk horses, and therapies such as intracecal buffering are helpful in preventing the shifts in cecal pH that can lead to laminitis.
In closing the first day of presentations, Dr. Joe Pagan spoke about gastrointestinal health, the foundation of which, he made clear, is good-quality forage. He identified four primary factors that affect forage quality: plant species, stage of maturity at time of grazing or baling, latitudinal effects (tropical versus temperate forages), and inhibitory substances that reduce digestibility of fibre and minerals.
The buffering capacity of certain forages is a burgeoning area of interest among equine nutritionists. Pagan explained that certain feeds and forages can counteract changes in gastric pH, thereby playing an important role in the prevention of gastric ulcers in horses. This ability to resist changes in pH is called buffering capacity.
Alfalfa hay has been shown to be effective in reducing the severity of gastric ulcers by providing superior buffering capacity when compared to grass hay. The second day of the conference featured several topics related to metabolic conditions. Dr. Anna Firshman, a large animal internist at Oregon State University, began the day with a thorough overview of insulin resistance, a problem that has been receiving much attention recently as it is thought to be closely associated with other diseases such as equine metabolic syndrome, equine Cushing’s disease, laminitis, hyperlipedemia, and osteochondritis.
Firshman reviewed the mechanisms of glucose transport in muscle and fat, and then described the tests that are currently available to assess insulin resistance in horses. Firshman concluded that though tests may become useful clinical means to assess the degree of insulin resistance and responses to treatments, there is no one ideal test that is both practical and accurate. Dr. Frank Andrews then settled onto the stage for a second presentation.
He presented a detailed outline of the metabolic-related conditions that most commonly affect horses: equine Cushing’s disease and equine metabolic syndrome. For each condition, he methodically outlined the clinical signs, diagnosis, course of treatment, and management goals.
For equine Cushing’s disease, Andrews stated that diagnostic tests, when coupled with clinical signs, will confirm the presence of advanced disease but may not be sensitive enough to detect early stages of the disease. KER has been instrumental in developing ideal growth curves for equine athletes. Dr. Clarissa Brown-Douglas reviewed the research compiled by KER over the last two decades, stressing the importance of properly feeding young, growing horses.
To fuel maximum growth, breeders often feed young horses large amounts of grain. However, rapid growth achieved by overfeeding energy has been implicated in developmental orthopedic disease (DOD). The source of energy may be important for many young horses. Those that experience an exaggerated and sustained increase in circulating glucose or insulin in response to a grain meal might be predisposed to osteochondritis dissecans (OCD).
Research conducted by KER suggests that hyperinsulinemia may influence the incidence of OCD. Based on the results of this research, young horses should be fed concentrates that produce low glycemic responses such as feeds in which energy is provided by fat and fermentable fibre sources (beet pulp and soy hulls). Once the audience had an understanding of the metabolic disorders that affect horses, Dr. Joe Pagan identified a commonality among them.
All of the problems are either triggered or aggravated by excessive starch and sugar intake. After a brief review of carbohydrates in horse feeds, Pagan gave general feeding recommendations for each disorder, noting that high-fat, low-starch feeds are appropriate for certain disorders such as tying-up but may not be recommended for others such as equine metabolic syndrome.
Once a horse has been diagnosed with a metabolic disease, an equine nutritionist and veterinarian should team up to formulate a suitable diet. Maintaining appropriate body condition is usually a trick for those who own horses diagnosed with a metabolic condition. These horses are often too thin or too fat. Dr. Laurie Lawrence, a professor at the University of Kentucky, addressed energy balance and methods to increase or decrease body condition.
She presented reasonable timelines for weight gain and emphasised management programs that allow ample time for weight gain so horses are not fed extremely high levels of concentrate. Lawrence also noted that as a horse is adapted to a diet with increased feed intake, there may be a fairly immediate increase in body weight due to changes in gut fill and/or gastrointestinal tissue mass, followed by a period of slower body weight change. Change in condition score will frequently lag behind change in body weight. Lawrence classified obese horses into two groups: those that have become fat temporarily because of a change in management or food availability, and those that have been fat for a long time.
Adjusting the body weight of the first group, Lawrence explained, is usually much less complicated than reducing the body weight of the latter group, and she gave a step-by-step approach to helping these horses lose weight. Kathryn Watts of Rocky Mountain Research and Consulting in Colorado gave the final presentation of the conference. She explained differences in the nonstructural carbohydrate (NSC) content in various forages, and how stage of growth and environmental factors might significantly alter the amount of NSC present. Watts advised that all of the most commonly recommended varieties of grass have the potential to contain high levels of NSC under certain conditions, but stands of these grasses can be managed for lower NSC concentration.
This year’s Kentucky Equine Research Nutrition Conference offered valuable information about gastrointestinal and metabolic problems affecting horses today. For those individuals unable to attend the KER conference, proceedings are available by logging on to www.shop.ker.com. This 150-page booklet contains a detailed paper for each of the lectures presented. As part of its dedication to world-class nutrition, KER has been recruited to help formulate and distribute feeds for the equine athletes of several international competitions.
In 2004, KER was named the official nutritionist of the United States Equestrian Federation. In this capacity, KER nutritionists use their knowledge to sort out nutritional challenges encountered by the world’s most elite equine athletes, those that represent the United States in international competition. For more information on KER, visit www.ker.com.
Feed Contaminants - how big a risk are they?
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.
Dr Catherine Dunnett & Dr Mark Dunnett (European Trainer - issue 22 - Summer 2008)
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 discernable 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 substances under racing rules and regulations.
There is some cross-over between plant toxins and prohibited substances, but it is the latter category that concerns us within this article. Prohibited substances Under the rules of racing commonly applied across Europe, a prohibited substance is defined as - a substance originating externally, whether or not it is endogenous to the horse, which falls into one of the following categories :
1. Substances capable at any time of acting on one or more mammalian body systems
2. Endocrine secretions and their synthetic counterparts
3. Masking agents Substance includes the metabolites of the substance and the isomers of the substance and metabolites. 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 categorised 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 In the UK, the Horseracing Forensic Laboratory (HFL) offers an equine feed testing service that screens for the presence of six commonly recognised contaminants, whereas in France a similar service provided by the Laboratoire Des Courses Hippique (LCH) includes an additional four contaminants in its testing procedure: Morphine UK/France Hyoscine UK/France Atropine UK/France Hordenine UK/France Caffeine UK/France Theobromine UK/France Theophylline France Bufotenine France Methylbufotenine France Dimethyltryptamine France 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 metabolised 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 recognised 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 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. Feed contamination with material from opium poppies (Papaver somniferum ssp. somniferum), wild poppies (P. somniferum ssp setigerum) or Oriental poppies (P. Orientale), resulting in post-race urine samples testing positive for opiates occurred in Australia in the 1990s and the UK and Ireland in 2002.
The spate of morphine positives in the UK and Ireland arose through the importation of contaminated raw materials; however it is possible that a home-grown problem could evolve in the near future as recent research has shown that the opium poppy grows quite widely in the wild in Ireland. 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 recognised 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 ultimately 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 maximise 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 recognised 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 the regulatory laboratories will be screening for these substances on a pan-European basis. 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 horse's 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 defence 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 offence, 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. Chris Gordon, Chair of the Feed Committee at the British Equestrian Trade Association (BETA), states that, BETA is at an advanced stage of discussion with individual feed manufacturers, the National Trainers Federation and the British Horseracing Authority in seeking to establish a Code of Practice for the production of feeds intended to be used in racing. It is anticipated that this will take the form of an appendix to existing accreditation through the UFAS feed safety system. Furthermore, in conjunction with our French and Irish counterparts, the CNEF and the Irish Grain and Feed Association (IGFA) and the European Horseracing Scientific Liaison Committee (EHSLC) we are attempting to establish a harmonised approach to feed testing for common contaminants across the major European horseracing jurisdictions. Within this framework we are hoping to establish common reporting levels or thresholds.
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.
Dr Catherine Dunnett (01 December 2007 - Issue Number: 6)
By Dr Catherine Dunnett
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.
From a practical viewpoint, I would say that the ability of a racing diet to support muscle glycogen synthesis remains important. 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.
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.