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NUTRITION
Feeding to support immunity A horse’s immune system is an exciting yet difficult area of research. Dr Catherine Dunnett takes a closer look into the potential ingredients that may offer highly beneficial support to horses in training Can diet affect immune status during training? The immune system in horses is complex and relies upon many functional elements to deliver a comprehensive defence against infection and disease. Foals are born with some natural immunity, which passes from mare to foal during gestation. Mare’s milk, particularly colostrum, also provides a further boost to early immunity through the presence of antibodies IgG, IgA and IgE and potentially some other components such as fructooligosaccharides, which are found in human breast milk. The horse’s immune system continues to develop through life, as exposure to different infectious agents leaves a legacy in terms of a ‘learned’ immune response. A well-tuned immune system in horses in training will ensure that many potential pathogens are prevented from gaining a foothold and causing infection or disease, whilst others are dealt with efficiently to minimise the effects of infection and to enhance the rate of recovery. It has been suspected for many years that both intense training and frequent travel can adversely affect the capabilities of the immune system, and the early stages of training seem to be particularly problematic in this respect. This is perhaps not surprising and, to draw an analogy, anyone with small children will appreciate the effect on health of their introduction to
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nursery or school. This situation is not unlike the initial stages of training where many relatively immunologically naive yearlings are thrust into a close environment and placed under some degree of physiological stress. Traditionally, feeding horses in training has primarily been about providing a balanced diet, in terms of nutrients including vitamins and minerals, with the emphasis being on providing an adequate intake of nutrients whilst avoiding excessive intake. Recently, however, the impetus in human nutrition has developed further to place greater emphasis on optimising the diet in order to maximise quality of life and resistance to disease. These goals are of great value to horses and additionally also offer the promise of ensuring that genetic performance potential is fulfilled. Immunity is of particular concern for racehorses, as it is for human athletes, as many days of training are lost through illness and no doubt many races have been lost due to horses performing below their ability due to sub clinical health issues. As a result, there continues to be great interest in the ability of both mainstream nutrients and functional foods, or nutraceuticals, to support the immune system. Dietary immunomodulation The impact of diet on immunity in horses is