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The Positive and Negative Effects of Oil in Equine Nutrition

NUTRITIONWeb Master

Published in European Trainer, January - March 2018, issue 60.

Oil is a regular addition to modern racing diets, either by feeding a high oil-containing racing feed or through extra addition of liquid vegetable oil. Research over the years has shown that oil is palatable to horses and digested very well, and that there is little difference in digestibility between the main types of vegetable-based oils used.

Oil that is integral to feed ingredients, such as that found in rice bran, linseed, naked oats, soya, etc., may have a marginally lower digestibility, as this will depend on how digestible the encapsulating matrix is to the horse. However, in the main both free oil and integral oil is well tolerated and digested in horses.  

In a natural environment, horses can easily consume between 2-3% of their body weight as dry matter from pasture. Oil has always been a natural part of the horse's diet, as grass contains about 2-3%, which may seem low but can provide the equivalent of 200-400mls of oil per day. Other forages, such as hay, haylage, and chaff, will also contain oil at a similar level on a dry matter basis.  

Horses can tolerate up to 20-25% of their total energy intake coming from oil, and this has been exploited successfully....

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Is EIPH beyond the scope of dietary change?

NUTRITIONWeb Master
  Is EIPH beyond the scope of Dietary Change?       Exercise induced pulmonary haemorrhage has been a concern to trainers for a very long time. The historic record of EIPH in horses such as ‘Bleeding Childers’, a son of the Darley Arabian, a founder of the modern thoroughbred, shows that ‘bleeding’ as it is commonly known is an age-old problem. The prevalence of EIPH during high intensity exercise,  such as racing, is relatively high, but influenced greatly by how it is diagnosed. For example, the prevalence of EIPH is quite low when the appearance of blood from the nostrils (epistaxis) is used as the diagnostic criteria. Unsurprisingly, it is much higher when more rigorous investigative techniques such as endoscopy or bronchioalveolar lavage are used.  Additionally, the prevalence increases when horses are repeatedly examined. In clinical terms, it has been suggested that if you look hard enough diagnostically, and often enough, almost all horses will show a degree of EIPH with racing at some time.  A large Australian study has also reported that there is a proven heritability or genetic element to this condition.       Notwithstanding this, EIPH presents a major concern for horses in training, as it often leads to loss in training days and may impact on race performance, although this seems to be dependent on the degree or grade of EIPH involved. A period of absence from the racecourse can also be a requirement of some racing jurisdictions, e.g. the British Horseracing Authority in the UK, following epistaxis, where blood is seen visually from one or both nostrils. Public perception is also relevant, especially when the public mood puts racing under tighter scrutiny in terms of animal welfare. There is also a mood for change with regards to the previously widespread use of pre-race medications, such as furosemide, (which has been widely used to treat EIPH) in countries such as the USA.  The Arabian Racing Organisation has recently announced that it will become ‘Lasix-free’ in the USA, which has been widely welcomed by trainers worldwide.        In some racing jurisdictions, nasal strips can be used which support the tissues of the nasal cavity helping to keep the upper airway fully open during exercise. There is evidence to suggest that nasal strips reduce upper airway resistance. Some prominent veterinarians and exercise physiologists have proposed that there is sufficient scientific evidence to support their use in the management of EIPH. However, despite being a non-invasive tool their use is not currently allowed in all racing jurisdictions including in the UK.       Whilst there is always a drive to discover new medications that will effectively control or treat EIPH within the rules of racing, diet and other complementary practices have always been of parallel interest to trainers.       The central paradigm to EIPH is that the membrane layer that exists between the alveolar air and the blood vessels is miniscule, representing a physiological cliff edge. This membrane must be sufficiently thin to allow efficient gas exchange, but this makes it very vulnerable to physical damage when under increased physiological stress, e.g. during hard work and racing when a massive increase in gaseous exchange is required.        From previous published research, EIPH seems to be a progressive disease, with time in racing being a significant factor. A current theory is that there is a progressive narrowing of the pulmonary veins, as a result of strengthening of these vessel walls due to smooth muscle expansion or hypertrophy, as well as collagen deposition in the vessels themselves.  Interestingly, in human studies where pulmonary hypertension (high blood pressure in the vessels supplying the lungs) exists, medics have also described calcium deposits or plaques in the pulmonary vessels, which would contribute to a loss of elasticity. This was also investigated in horses in a Canadian study of 108 racing horses that had died or were euthanized. In this study, the authors found a high presence of calcium deposition within the tunica media (muscular middle layer) of the pulmonary arteries.        My interest of course is due to the dietary implication of this theory and it may be an example of barking up the wrong ‘vitamin tree’. Vitamin K has featured for many years in supplements seeking to nutritionally address the issue of EIPH in the miss-held belief that inappropriate clotting is involved in its mechanism. Vitamin K has a well-defined role in clotting and largely synthetic forms of vitamin K (menadione) have been employed in equine nutrition to ‘solve’ this non-issue. However, vitamin K also has a central role to play in calcium homeostasis by activating GLA proteins in the body, including osteocalcin and matrix GLA protein.  Matrix GLA protein is responsible for scavenging calcium from areas of unwanted deposition such as blood vessel walls and soft tissue and driving its repatriation back into bone.  ‘Dr Green’ seems to be on the case again, as vitamin K1 (phylloquinone), the predominant natural source of which is actively growing green pasture, holds the key to activation of these GLA proteins in horses. The widely used synthetic vitamin K or menadione does not exhibit this function. It would certainly be interesting to see whether activation of GLA protein is sub-optimal in EIPH-positive horses compared to EIPH-negative horses. Fresh and actively growing grass is of course notably absent from most racing diets, with the exception perhaps of places like New Zealand. It is also noteworthy that vitamin K1 in the normal diet is unstable and is rapidly lost from pasture that is converted to hay or haylage or other harvested forage (see previous European Trainer article, Vitamin K- the forgotten vitamin).         The overarching focus of nutrition in relation to EIPH has been to tackle perceived pinch points, or potential weakness, in the horse’s physiological systems that may contribute to the expression of EIPH. Typical areas for focus have been collagen synthesis, blood clotting, inflammation, respiratory challenge, water balance and haemodynamics. Given that at the current time research scientists do not have a definitive explanation of the mechanism or aetiology for EIPH and there are no treatment options with 100% certainty, it is difficult to see how a simple dietary intervention could prevent EIPH in isolation. However, nutrition offers a relatively benign method to potentially reduce some of the risk factors that may be involved in the expression of EIPH and potentially reduce its severity.         Vitamin C, either in isolation or in combination with other nutrients with antioxidant activity, has also been looked at in relation to airway inflammation and capillary fragility which could be regarded as risk factors for EIPH. Vitamin C is the main water-soluble antioxidant found in lung lining fluid and is also required for a key stage in collagen synthesis, which adds strength to blood vessel walls. Whilst no direct benefit of vitamin C on the instance of EIPH has been reported, there are several studies which suggest an improvement in airway inflammation as a consequence of supplementation. Certainly, as part of a multifaceted approach, normalisation of airway inflammation must surely be beneficial. However, supplementation is not necessarily the answer, as a good racing diet should provide sufficient antioxidants and their co-factors and horses do not have a dietary requirement for vitamin C under normal circumstances. However, clinical need supplementation with a bioavailable form of vitamin C may be a benefit.       Airway inflammation is certainly an issue in horses in training and any measure to normalise this should be beneficial. A low-dust environment, high-quality feed and forage with a microbiological fitness to feed being essential. Feeding haylage or hay, in conjunction with an appropriate proven protocol for steaming will also help to reduce the drivers of airway inflammation to which horses in training can be exposed.        Nitric oxide is a vasodilator through its action in relaxing vascular smooth muscle and it is produced locally by the action of nitric oxide synthase. Some feed supplements have drawn on this action to suggest the benefit of various ingredients that act as precursors or stimulants of nitric oxide synthesis, although, a clinical trial to investigate the effect of inhalation of nitric oxide resulted in a negative effect on EIPH.         Omega 3 fatty acids have been investigated for their ability to increase the fluidity, flexibility or ease of travel of red blood cells through blood vessels, which could potentially reduce resistance to the flow of blood during exercise. Additionally, omega 3 fatty acids are anti-inflammatory in nature compared to their omega 6 counterparts, which may also have some beneficial effect on airway inflammation. There have been three studies now published in horses that suggest that supplementation with long chain fatty acids DHA and EPA can at least reduce the severity of EIPH. The omega 3 fatty acid content of a racehorse’s diet is normally quite low, as pasture represents one of the most significant sources under normal conditions.  Analysis of Ryegrass, Fescue and Orchard grass in Canada has shown that the parent omega 3 fatty acid alpha linolenic acid is quantitatively the most significant fatty acid in pasture.  However, the conversion of linolenic acid to the physiologically more functional DHA and EPA is relatively inefficient at about 5% conversion. Other ingredients such as salmon oil, tuna oil and certain algae can offer a richer source of DHA and EPA, although this must be balanced against the volume of pasture and hence linolenic acid that could be potentially be consumed by a horse at pasture for part of the day.       In summary, it is very unlikely that there are any nutritional panaceas for EIPH at present, or on the horizon. However, there are a few practices and nutritional factors, which collectively under veterinary supervision may help to move horses at risk of EIPH a little further away from the proverbial cliff edge. In addition, the availability of pasture, in terms of omega 3 and vitamin K1 intake, as well as the beneficial effect of a non-stable environment on airway inflammation should perhaps be investigated further in horses at risk of EIPH. However, given the suggested genetic component to this disease the question of desirability perhaps needs to be asked in parallel.        
 

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Exercise induced pulmonary haemorrhage has been a concern to trainers for a very long time. The historic record of EIPH in horses such as ‘Bleeding Childers’, a son of the Darley Arabian, a founder of the modern thoroughbred, shows that ‘bleeding’ as it is commonly known is an age-old problem.

The prevalence of EIPH during high intensity exercise,  such as racing, is relatively high, but influenced greatly by how it is diagnosed. For example, the prevalence of EIPH is quite low when the appearance of blood from the nostrils (epistaxis) is used as the diagnostic criteria. Unsurprisingly, it is much higher when more rigorous investigative techniques such as endoscopy or bronchioalveolar lavage are used.  Additionally, the prevalence increases when horses are repeatedly examined. In clinical terms, it has been suggested that if you look hard enough diagnostically, and often enough, almost all horses will show a degree of EIPH with racing at some time.  A large Australian study has also reported that there is a proven heritability or genetic element to this condition.

Notwithstanding this, EIPH presents a major concern for horses in training, as it often leads to loss in training days and may impact on race performance, although this seems to be dependent on the degree or grade of EIPH involved. A period of absence from the racecourse can also be a requirement of some racing jurisdictions, e.g. the British Horseracing Authority in the UK, following epistaxis, where blood is seen visually from one or both nostrils. Public perception is also relevant, especially when the public mood puts racing under tighter scrutiny in terms of animal welfare.

There is also a mood for change with regards to the previously widespread use of pre-race medications such as furosemide (which has been widely used to treat EIPH) in countries such as the USA.  The HH Sheikh Mansoor Bin Zayed Al Nahyan Global Arabian Horse Flat Racing Festival had recently announced that its races in the US will be ‘lasix-free’, which has been widely welcomed by trainers worldwide.

In some racing jurisdictions, nasal strips can be used which support the tissues of the nasal cavity helping to keep the upper airway fully open during exercise.

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Does nutrition factor in injury, repair and recovery?

NUTRITIONWeb Master
  Lost training days through injury or infection are problematic for trainers, both practically and commercially. It is a stark fact that 50% of thoroughbred foals, bred to race, may never reach the racecourse.  In young thoroughbreds, musculoskeletal problems have been cited as the most common reason for failure to race and this appears to continue to be a major issue for horses in training.  An early study carried out in 1985 in the UK reported that lameness was the single biggest contributor to lost days of training, and subsequent research 20 years later found that this was still the case, with stress fractures, which involve normal bone being exposed to abnormal stress, being cited as a significant underlying cause.  Perhaps not surprisingly, two-year-olds were more susceptible to injury than three-year-olds.  Whilst there are of course many other reasons – including muscular issues such as tying up, respiratory problems, and viral infection – why horses may fail to train, in this survey medical issues accounted for only 5% of the total training days lost.         Balance between damage and repair processes are imperative    There are many factors that affect the chance of injury in thoroughbreds in training, including genetic predisposition, conformation, and training surface.  Style and type of training, in terms of frequency and intensity and how this is balanced through recovery protocols, is also likely to be a significant factor in the incidence of injury.  The nature of training means that a balance between damage and repair processes are imperative.  Physiological systems need to be put under stress to trigger a suitable training response, which inevitably involves a degree of micro-damage.  However, inadequate or ineffective recovery protocols can allow micro-damage to accumulate, as the repair processes fails to keep pace.  Vigilance is certainly important, as very early diagnosis and veterinary intervention, or even in some instances prophylaxis, is likely to form a key part in reducing injury rates.           A cursory glance may lead you to think that nutrition can have no significant role in either prevention of injury or disease or indeed recovery.  However, when we stop to consider the typical physiological and biochemical processes involved in injury or disease including inflammation, cell differentiation, immune response -- for example in bone and cartilage turnover -- it is perhaps easier to appreciate why good nutrition should provide an important part of the strategy to reduce training days lost to injury or infection.         Strong immune system is important to support recovery and repair    Good clean forage, whether hay or haylage, has dual importance.  Firstly mould, bacteria, and dust, or respirable particles, are a major contributory factor in the development of respiratory disease and so simple steps such as analysis of hay prior to use, or steaming hay, can help.  Secondly, adequate forage in the diet is important to maintain a healthy microbial balance in the hindgut and to offset the negative impact of starch that may escape digestion in the small intestine. The gut is probably one of the most important organs with respect to immunity, as 70% of the cells of the immune system reside here. The horse’s immune system is not, however, just involved in prevention and recovery from disease, but is intimately involved in repair processes throughout the body.  For example, following muscle damage, local immune cells infiltrate muscle to help remove the damaged muscle cells and then other immune cells including T-cells interact with stem cells, which are like cell templates, stimulating them to become new muscle cells. Development and repair processes are dependent on a well-functioning immune system, and studies in rodents suggest that these processes may be less efficient when immune function is compromised.           The immune system in horses in training is placed under pressure during training and over-training, which is an immune-mediated process, and can increase the potential for infection or injury.           A well-balanced diet in terms of an appropriate ratio between forage and concentrate, optimum good quality protein for delivery of important amino acids, and an optimum and not excessive intake of a wide range of micronutrients and vitamins, is important to support the immune system.  Nutrients that have been highlighted as particularly important include the amino acids arginine and glutamine, as well as omega-3 fatty acids and a variety of antioxidants.  There are also secondary measures that can be taken to support the immune system via the digestive tract. Some of these are adequate forage intake, managed starch intake, and small meals.  Probiotic ingredients, such as live yeasts, or prebiotics such as mannan-oligosaccharides, may also be beneficial.         Low glutamine status may reflect an immune system under stress    Glutamine is an amino acid, which is naturally present in the diet, but is conditionally essential.  This means that increased dietary intake of glutamine may be beneficial under certain circumstances such as infection, stress, or hard training.  Glutamine is an important energy source, in place of glucose, for cells of the digestive tract and the immune system.  Reduced availability of glutamine during times of increased requirement may compromise the immune system.  In humans, a reduction in the level of glutamine in plasma is associated with a decrease in the ability of lymphocytes (white blood cells) to multiply themselves in response to an invading pathogen.  In horses, plasma glutamine is severely depleted during viral infection but can be boosted through supplementation of the diet.  European feed legislation, however, prevents the addition of the amino acid L-glutamine to horse feeds or supplements.  Glutamine-rich peptides, or protein sources such as whey, which is rich in glutamine, can be used in its place. Human studies suggest that there may be a role for glutamine during training, as glutamine status is reduced with prolonged intensive training, where the over-training syndrome is a risk.              Omega’s balance immunity and inflammation    Omega-3 fatty acids are also of interest, having a reputed beneficial effect on the immune system and an anti-inflammatory effect, which is of relevance for the general damage and repair processes, as well as for respiratory health.  The omega-3 content of a racehorse’s diet can be relatively low, as the omega-6 family of fatty acids prevail in ingredients like cereals, soya, and most vegetable oils.  Interestingly, the omega-3 fatty acid content of grass is considerably higher, so access to pasture will improve the ratio between omega-3 and omega-6 fatty acids in the diet.  This has been shown in beef cattle and the milk of dairy cattle that are pasture-fed.  Alfalfa and hydroponic grass should also boost the omega-3 content of the diet.  Alpha linolenic acid  is the most prevalent omega-3 from plant sources and is reduced considerably in mature forage.   Linseed is also a rich source of alpha linolenic acid, and canola oil has a higher omega 3:6 ratio compared to soya or corn oil.  The physiologically active longer chain omega-3 fatty acids, such as docosahexanoic acid (DHA), are synthesised from alpha linolenic acid, although this process is a relatively inefficient conversion.  Ingredients such as salmon oil or algae, rich in DHA, have been used to directly supplement the equine diet with DHA.           With injury comes inflammation, which may last a few hours, a few days, or even a few weeks, and this is a normal and essential part of the start of the healing process, as it triggers a cascade of reactions that promotes healing.  Whilst it is acknowledged that excess or prolonged inflammation is undesirable, uncontrolled use of nutrients with anti-inflammatory action may equally not always be beneficial.          Dr Green offers skeletal support    Lameness remains the single most common cause of loss of days to training for young racehorses. Whilst muscle fatigue is part and parcel of training and racing, it is worth reflecting that many injuries occur when muscles are tired and being pushed too far beyond their comfort zone.         Retaining bone density, as well as maintaining a positive balance between damage and repair processes, is key in retaining skeletal integrity. Skeletal foundations have been laid in utero and during the rapid growing phase in horses, much of which is largely out of a trainer’s control.  The trainer’s target is to provide a diet that maintains the integrity of the skeletal system, to retain bone density, and to promote healing once training commences.           When yearlings first move into racing yards, they usually experience a significant change in their diet that has consequences for bone metabolism.  This comes at a time when they may still be growing and the skeletal system is put under considerable strain.  Whilst at stud farms, the largely grass-based diet fosters good calcium absorption from the digestive tract, as well as the retention of calcium within bone and reduced urinary losses.  However, once in race training, the absence of pasture, reduction in forage, and increase in high cereal-containing concentrates is characteristically paralleled by a reduction in bone density seen in horses in early training.  In the past, this has been attributed to a lower dietary cation-to-anion basis of the diet, which indirectly affects calcium balance through concomitant hormonal action on absorption, resorption, and excretion of calcium.   This has commonly been addressed by adding more calcium in the diet.  However, there is perhaps a rationale for limiting the intake of cereals and maximising forage intake to support the skeletal and other body systems.           Whilst the intake of calcium and phosphorus are important during training, other nutrients such as vitamin D have a vital role to play in proper absorption of calcium and phosphorus, as well as acting as the gatekeeper for the resorption of calcium from bone.  Equally, another of Dr Green’s gifts is vitamin K1, which through its effect in activating osteocalcin and matrix GLA protein firstly directs calcium to bone and then helps cement the mineral within the structure of bone to sure-up bone density. Silica is another feed ingredient that has been promoted to support bone density and integrity during training.         Curiously, pasture – an ingredient that seems to offer such benefits to horses in training – is not always available as part of the in-training diet, which perhaps should trigger some pause for thought. Whilst nutrition is certainly not the answer in isolation to reducing injury rates in racehorses, a balanced progressive diet can offer several elements of support as part of a well-structured training regime.

First published in European Trainer issue 58 - July - September 2017

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Lost training days through injury or infection are problematic for trainers, both practically and commercially. It is a stark fact that 50% of thoroughbred foals, bred to race, may never reach the racecourse.

Lost training days through injury or infection are problematic for trainers, both practically and commercially. It is a stark fact that 50% of thoroughbred foals, bred to race, may never reach the racecourse.  In young thoroughbreds, musculoskeletal problems have been cited as the most common reason for failure to race and this appears to continue to be a major issue for horses in training.  

An early study carried out in 1985 in the UK reported that lameness was the single biggest contributor to lost days of training, and subsequent research 20 years later found that this was still the case, with stress fractures, which involve normal bone being exposed to abnormal stress, being cited as a significant underlying cause.  Perhaps not surprisingly, two-year-olds were more susceptible to injury than three-year-olds.  Whilst there are of course many other reasons – including muscular issues such as tying up, respiratory problems, and viral infection – why horses may fail to train, in this survey medical issues accounted for only 5% of the total training days lost.

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The New Superfoods in Equine Nutrition

NUTRITIONWebmaster

Nature’s basket offers a rich source of beneficial nutrients, including phytonutrients.  Horse owners and trainers have always been interested in what these sometimes relatively un-researched ingredients can offer for the health and performance of horses in training.  In this article, I explore three ingredients that have become popular components of supplements and also as stand-alone products.

Equine Metabolic Syndrome

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Trickle feeding - more in tune with nature

NUTRITIONWebmaster

In evolutionary terms, we have been racing horses for a fraction of time compared with the millions of years that these wonderful animals have roamed the earth. The structure and physiology of their digestive system has evolved over this time to reflect their natural feeding patterns, which will have been greatly influenced by availability and quality of food. 

The challenge of feeding globetrotting horses

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European horses will commonly travel to Dubai, Australia, Japan and America - how much notice is given to disruptions to the diet with movement from country to country? Not only can performance be marginalised but colic is a high risk factor. Dr Catherine Dunnett looks into the challenges of feeding globetrotting horses.

How eating aids the skeletal structure

NUTRITIONWebmaster

It has been said that 'equine conformation evaluates the degree of correctness of a horse's bone structure, musculature and its body proportions in relation to each other.' This is undeniable, but there is remarkably little information in published literature regarding the importance of the position of the head, despite the fact that this has a direct effect on balance, posture and subsequent performance.

The horse is documented as a prey species and as such retains, despite domestication, ares of hyper-sensitivity in loins, abdominal tunic, and poll; pain experienced in any of these areas, no matter the cause, gives you a rise to an immediate fright, flight and/or flight response.