Trainer Magazine

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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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