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Thread: Nutrition ...... endurance hossss

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    Default Nutrition ...... endurance hossss

    Uni assignment can lay press it

    1.0 Introduction

    The endurance horse must maintain a moderate speed over a long distance, conditioning for this at elite level can take three years. The correct balance on feeding is vital for the horse to perform at the highest level and maintain an appropriate pace to place well at the end of the competition (Clayton, 1991; Kohnke, 1992).

    The ideal horse for the job has been found to be the Arabian or an Arabian cross (kohnke, 1992), due to their small stature, light weight; small size with little body fat, small bone and lean muscles that are indicative of a horse with a high aerobic capacity (Clayton, 1991) Frape, 2004, concurs with the last statement by stating that the endurance horse requires a predominance of muscle fibres that are capable of slow contraction (slow twitch, high oxidative fibres) but resistance to fatigue. All these factors collectively make the horse predisposed to being able to complete an endurance event successfully.
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    Before considering the diet the horse requires for the job other aspects of the competition and training must be well thought-out, the preferred metabolic pathway for the nutrients to be supplied, the energy pathway used, also the timing of the competition and how long it lasts.




    2.0 Optimum nutrition to support the endurance horse in training and competition

    2.1 Energy pathway
    There are two energy pathways within the body, aerobic and anaerobic. Aerobic respiration is the use of energy from organic nutrients in the presence of oxygen whereas anaerobic respiration meaning without oxygen (Warren Evans, 1992; Lewis, 1995). Endurance is predominantly an aerobic sport (Clayton, 1991).

    Aerobic respiration relies on the body’s ability to get oxygen from the atmosphere to the muscle cells within the body efficiently so that it can be used to utilize the energy in food using the preferred metabolic pathway. Whether there is sufficient oxygen present in the muscle cells will depend on the speed and the extent of training of the individual horse, but if there is not enough oxygen then the pathway will switch to anaerobic, this in turn produces lactate acid which is measurable in the blood stream. The threshold of exercise-induced lactate accumulation is taken to be 4 mmol/l in the plasma (Frape, 2004). Clayton (1991), states that good endurance horses will finish the race with less than 4 mmol/l this then shows that they work below their anaerobic thresholds in competition working using aerobic respiration.

    Clayton, 1991, states that successful endurance horses generally have a resting heart rate that is very low; this can suggest that they have a large, muscular heart that can contract strongly. A study conducted by Young et al. (2005) in young elite and non-elite thoroughbred racehorses, proved the existence of a correlation between the horses athletic performance, heart size and the maximum oxygen uptake lead to increased performance, it can therefore be deduced that the ratings given to a horse by the British Horse-racing Board, represent a reasonably precise account of the horse’s ability, after a relationship between echocardiograph measurements of the left ventricle. Increased mass and wall thickness, promote increased performance through correct training.

    The amount of oxygen taken up by the muscles is referred to as Vo2 max (Young et al., 2002) although Evans & Rose (2006) illustrate that Vo2 max can be limited due to the cardiovascular transportation of oxygen within the blood flow thus potentially limiting performance. Therefore also can be improved by better cardiovascular transportation of oxygen, this can be achieved through correct training and nutrition management. Vo2 max is a measure of function of the cardio-respiratory system alongside representing the maximal muscle function aerobically (Kearns et al., 2002) thus a measure of the maximum aerobic capacity can be identified (Hodgson & Rose, 1994). This information is an important factor in the management of the endurance horse.

    2.2 Metabolic pathway
    The main productive function in the horse is work, the driving forces behind types of equine performance is the conversion of chemically bound energy from food into mechanical energy from which muscular movement can be gained (Pagan, 1998). This energy is derived from the dephosphorylation of adenosine triphosphate (ATP) to adenosine diphosphate (ADP). In order for muscular moment to continue, ADP must be rephosphorylated to ATP at a rate equal to the rate of ATP use (Lewis, 1995). The quickest way to form ATP is by the use of another compound, creatine phosphate (CP), however the muscle contains only a small amount of CP and ATP and this supply is exhausted in a short duration (Pagen, 1998; Frape 2004).

    So for prolonged exercise there are other ways in which ATP is resynthesized; Oxidative phosphorylation, where by carbohydrates, fats and proteins are broken down into energy (ATP) with a supply of oxygen, an aerobic reaction. There is also gycolysis, where by glucose or glycogen is broken down into pyruvate in the muscle cell without the use of oxygen, this is an anaerobic reaction as it does not require the presence of oxygen (Pagan, 1998; Frape, 2004). The pyruvate can be further broken down as can fatty acids but this demands the presence of oxygen, this will only take place in the mitochondria and through that is known as β – oxidation of fatty acids and the Tricarboxylic cycle (TCA) cycle (Frape, 2004).

    It has already been concluded that the endurance horse uses predominantly aerobic respiration, and therefore the aerobic pathway to gain the energy needed for sustained exercise. If for a short period the energy pathway switched into anaerobic and the metabolic into just glycolysis, during say a hill climb and only short intervals. It was seen that that good endurance horses will finish the race with less than 4 mmol/l of lactate in the blood plasma therefore the pyruvate is broken down on switching back to aerobic and the anaerobic pathway is not of predominate use. Fatigue in the endurance horse is more likely to come from glycogen depletion rather than from lactic acid accumulation (Pagan, 1998; Clayton, 1991).

    In carbohydrate metabolism, first glycolysis takes place within the cell cytoplasm, one glucose molecules is split into two fragments with three carbon atoms, each of these then goes on to be converted in pyruvic acid by a chain of reactions. Then will continue into the TCA as acetyl-CoA, the TCA take place within the mitochondria of the cell, this requires oxygen to the organelles and that carbon dioxide is removed to the blood stream. The acetyl-CoA will then enter the cycle and move round, in a series of dehydrogense reations, and moves round two times to produce a net yeild of 38 ATP molecules (Lewis, 1995; Frape, 2004).

    In the endurance horse fatty acids will be metabolised as this can yield twice as much energy compared with carbohydrates. First the molecule undergoes β – oxidisation to split into acetyl-CoA, which can then enter the TCA. When larger quantities of fatty acids are dissimilated in β - oxidisation to acetyl-CoA, the cycle turn must accelerate. In extended work of the trained endurance horse there will be no difficulty in breaking down fatty acids to carbon dioxide as there is sufficient oxygen taken in by respiration (Frape, 2004).

    The maintenance of the heart rate and keeping the horse working aerobically (around 120-150 beats/min) also lies with the rider, taking into account that the horse will set out excited and fast, so warm up before hand, during the race assess the weather conditions, heat, humidity as well as terrain and altitude with can affect the energy expenditure and adjustments made accordingly to keep the horse from becoming fatigued (Clayton, 1991).

    At a slow pace type I fibres are primarily recruited and energy generation is completely aerobic, at this speed the main supply is fat. Fat stores are plentiful and they can be mobilized and metabolized fast enough to meet the demand. As speed increases from walk to trot to canter type I fibres cannot contract fast enough therefore type IIA are recruited as well. These are also aerobic but require a combination of glycogen and fat for energy release. Glycogen can be metabolized aerobically 2 times as fast as fat can for ATP generation, so as speed increases fat is too slow a fuel for energy generation, but as endurance horses tend to maintain a constant speed at a trot or slow canter in places fat is going to be a predominate fuel source. The greatest store of fuel within the equine body is within the adipose tissue, 40,000grams in a 450kg horse compared to within the muscle 3,150-4,095 of glycogen, showing that fat is the most available fuel, if working correctly so it can be utilised (Pagan, 1998).



    2.3 Nutrition
    Once the horse is in training for competition it is older than four so duel demand for energy in growth as well as exercise is not necessary. Therefore it is only needed to be considered to feed for exercise and repair. Energy will be obtained from carbohydrates, proteins and fats within the horse’s diet (Kohnke, 1992).

    The most important components for the endurance horse are good quality forage and water; most horses are trained if possible out of pasture of good quality, needing only small amounts of concentrate. If fed hay to be fed at a rate of 2-2.5% of body weight a day, therefore an elite horse weighing 450kg would need about 10kg of hay daily (Kohnke, 1992; Clayton, 1991). This is quite easy and practical management, especially if out at good pasture, but it must be remembered to check the fields and rotate and move accordingly, so that the horse’s requirements are met is. Adequate intake of fibre from the grazing or hay is essential to maintain efficient and healthy digestive function, especially on high grain or fat diets (Kohnke, 1992). Meyer (1987) supported this concluding that endurance horses should have large amounts of roughage daily as this dilates the large intestinal volume and increases water and electrolytes reserves.

    Grains should be given to the horse daily to maintain weight and performance, these should not be feed exessivly and 2-3kg/day is normally quite adequate for an elite horse in hard training (Clayton, 1991). Fat, such as corn oil can be added to the diet, as it can provide a reservoir of energy for endurance exercise (Kohnke, 1992). Pagan (1998), found that feeding fat to horses resulted in a greater mobilisation and utilisation of fat during long distance exercise, but it was found the horses fed high fat diet and lower muscle and liver glycogen storage therefore it is important to supply adequate starch within the diet also. A horse has to be conditioned to a high fat diet, but once done so volumes of up to 1 litre a day can be supplemented to the feed without risk or metabolic upset, but only about ¼ of a litre is required (Kohnke, 1992). Fat also decreases the amount of energy used for heat production which decreased the horse’s heat load, particularly helpful if in a warm or humid climate. High fat diets have been shown to enhance performance and delay fatigue (Lewis, 1995).

    Protein need in the adult horse is relatively low, and it is not a great energy source, it is also expensive. Up to six times more heat is generated from protein being utilised for energy, this in the endurance horse would not be preferable, studies confirm this in higher protein diets in horses performing long sub-maximal work (Lewis, 1995). Most do well on a diet of around 10% provided in grain, alfalfa or mix hay (Kohnke, 1992).

    Vitamin E and B complex vitamin are required to maximize stamina and muscle function around 1000-2000IU, particularly when increased levels of fat is provided (Kohnke, 1992).

    There is a great deal of sweat loss, electrolyte supplementation is required, three parts sodium chloride to one part potassium chloride is added to feed at rate of 1-4 tablespoons a day, dependant on horse and climate. Free access to water must be given and an additional block of salt also (Clayton, 1991).

    Meyer (1987) stated that horses should be fed at least five hours before a race as this will allow the feed to have passed the ileocaecal orifice, Ralston (1988) supported this in finding that horses failing to complete at 160km races have received mixtures containing less hay and more grains. Water should be freely available at all times, fibre and electrolytes in the feed should encourage the horse to drink and the fibre aid the retention of water in the gut as a reservoir. At rest stops water should be provided and eletrolytes the horse should be trained to drink at every opportunity No feed should be given as it can cause earlier fatigue when ride continues (Clayton, 1991; Kohnke, 1992).

    There are a range of performance enhancing neutraceuticals that can be used, from those such as joint supplements to support the working horse that are allowed under FEI and sporting bodies to ones which are illegal, there are always ongoing debates and substances being added to the lists. Therefore as a competitor or groom to an elite competition horse it is important that the knowledge of what is acceptable is kept up to date.

    2.4 Ergogenic aids
    Ergogenic aids are factors that can increase or improve work production and therefore performance; they must affect some aspect of exercise physiology. Obviously in the competition sense it is preferable that improve an aspect that is limiting to the athlete (Lawrence, 1998).

    Coyle (1984) suggests the ergogenic aids can function in the subsequent ways; they may act as a supplementary fuel source for energy production. They may affect the flux of fuels through the energy pathways. They may delay or minimize the effects of end product accumulation, such as heat or lactic acid and they can affect the nervous system by affecting coordination, recruitment of muscle fibres or psychological effect.

    It is hard to determine whether ergogenic aids actually work or not, there is little research even when animal and human studies are considered as a whole. In studies that have been performed the method can be highly questioned, there is also the problem that there are so many factors to performance on an individual day that it can be hard to pinpoint whether it is the aid affecting the result/performance or another variable. There needs to be a very large sample size and repetitions. The following are reputed to have an ergogenic benefit, B vitamins, antioxidants and haematinics, which are blood builders (Lawrence, 1998).

    Hargreaves, et al., 2002, found that the endurance horses had increased activities of enzymatic antioxidants and muscle cell enzymes which may reflect oxidative damages as they are indicative of muscle cell leakage. Oxidative stress is a damaging imbalance in the oxidative-anti-oxidative system of cells, it could damage DNA and lead to aging and damage of the cell membranes They then suggest after the study was concluded that there be testing of antioxidant supplements administered before and during a race, this could if helping the issue improve the performance and the welfare of the endurance horse.

    There is also the ethical consideration of ergogenic aids as they aim to improve performance. The IOC (International Olympic Committee) doping legislation states that any physiologic substance taken in abnormal quantities with the intention of artificially and unfairly increasing performance should be construed as doping, violating the ethics of sport performance (Harris & Harris, 2001).





    3.0 Conclusion

    Feeding the performance horse is very practically based, but the background knowledge of energy pathways and metabolic pathways must be utilised for both the performance, well being of the horse and for cost effective management.
















    References

    Clayton, H.M. (1991) Conditioning Sport Horses. Canada; Sport Horse Publications

    Coyle, E.F., (1984) Ergogenic aids. Clinical Sports Medicine 3 (3), pp 731

    Frape, D. (2004) Equine Nutrition and Feeding. 3rd Edition. Oxford; Blackwell Publishing
    Hargreaves, B.J., et al., (2002) Antioxidant Status of Horses during Two 80-km Endurance Races. The Journal of Nutrition. 132, pp 1781-1783
    Harris, P.A, & Harris, R.C., (2001) Nutrition ergogenic aids in the horse- uses and abuses. Advances in Equine Nutrition II. Nottingham University Press. pp491-507
    Hodgson, D.R., & Rose, R.J (1994) The Athletic Horse: Principles and Practice of Equine Sport Medicine. Oxford; Elsevier Health Sciences

    Kearns, C.F. (2002) Relationship between body composition, blood volume and maximum oxygen uptake. Equine Exercise Physiology 6, pp 485-490

    Kohnke, J. (1992) Feeding and Nutrition, The making of a champion. Austrialia; Birubi Pacific
    Lawrence, L.M., (1998) The use of nutritional ergogenic aids in horses. Advances in Equine Nutrition. Nottingham University Press. pp191-199
    Lewis, L.D., (1995) Equine Clinical Nutrition, Feeding and Care. London; Williams & Wilkins
    Meyer, H., (1987) Nutrition of the equine athlete. Exercise Physiology 2, pp. 644-673 California; ICEEP Publications.
    Ralston, S.L., (1988) Nutritional management of horses competing in 160km races. The Cornell Veterinarian. Pp53-61
    Rose, R.J & Evans, D.L (2006) Cardiovascular and Respiratory Function in the Athletic Horse. Equine Exercise Physiology 2, pp 1-2

    Warren Evans, J. (1992) Physical Condition of the horse. In: Stull, C.L. Horse Breeding and Management. London, UK: Elsevier. 1992. pp50-60

    Young, et al., (2002) Heart size estimated by echocardiography correlates with maximum oxygen uptake. Equine Exercise Physiology 6, pp 467-471

    Young, et al., (2005) Left ventricular size and systolic function in Thoroughbred racehorses and their relationships to race performance. Journal of Applied Physiology 99, pp 1278-1285

    Oh how I miss you, my symphony, played the song that carried you out.

  2. #2
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    Very interesting, reads well

    Alternatively buy Welsh cob, don't feed it, and still have mucho endurance fun

    Granted we are not up to Golden Horseshoe standard yet though.....if we up the distance I may have to consider feeding

  3. #3
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    Was to be a top competition horse... xxx

    Oh how I miss you, my symphony, played the song that carried you out.

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