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Trainer Magazine - the horse racing magazine for the training and development of the thoroughbred racehorse. Europe and North America.

To beet or not to beet? - Will beetroot become part of the racehorse’s diet?

BROWSING the supermarket shelves today you may have noticed that beetroot can now be found in the juice section – it has become very popular in this form. A resurgence of interest in beetroot is largely due to new information available on its health benefits and some scientific research reporting a potential benefit for exercise performance. In the last two years, I have come across two trainers that have incorporated beetroot juice into their horses’ diets. In this article, I will outline the reputed beneficial effects of beetroot for human athletes and discuss its relevance for horses in training. Beetroot (Beta vulgaris) is a root vegetable from the same family as sugar beet, the latter of which is commonly used in equine diets. Beetroot grows well in Europe and is also commonly grown in North and South America. The nutritional profile of beetroot is good and includes a relatively high protein and fibre content, coupled with low oil; starch and sugar (see Table 1). Characterised by an intense red colour, beetroot contains a number of antioxidant pigments including polyphenols, such as resveretrol and quercetin. The main red pigment in beetroot is known to be betanin, a glucoside that is used as a natural food colouring agent. Betanin is also recognised as a natural antioxidant, which may in itself bring health benefits. However, when beetroot is eaten in significant amounts, this red pigment can lead to a pink colouring of both urine and faeces in people, although whether this phenomenon (known as beeturia) occurs in horses is currently unknown. By far the most interesting and potentially exciting effect of beetroot lies in its naturally high nitrate content. Nitrates (NO3) belongs to a family of compounds that contain nitrogen and oxygen. They are found in varying amounts in plants and vegetables and certain vegetables such as beetroot are regarded as being a very rich source, whilst others such as carrots only have a moderate to low level (Table 2). Researchers have suggested that the health benefits attributed to a high vegetable- containing diet in people may actually be largely due to a parallel increase in nitrate intake. Specific research on beetroot has reported a beneficial effect on blood pressure and also on exercise tolerance. In people, the nitrate from beetroot is absorbed in the stomach and small intestine into the blood. A proportion of this circulating nitrate is then concentrated in the salivary glands. Once in saliva, the nitrate is broken down by bacteria in the mouth to form nitrite. Nitrite is then absorbed, or broken down further to nitric oxide once in contact with stomach acids. Absorbed nitrite then can also be broken down to nitric oxide in the circulation following the consumption of beetroot. Nitric oxide has a wide range of physiological effects within the body, but specifically is believed to bring about a reduction in blood pressure, as nitric oxide opens up or dilates blood vessels allowing blood to flow more easily. Consuming beetroot immediately before exercise or supplementing chronically for 3-15 days in humans has also been reported to improve the economy of sub-maximal exercise by allowing energy to be generated more efficiently with less oxygen used (~10% less). Run time to fatigue during maximal exercise has also been improved in humans by 15-20% following beetroot supplementation. There has not been any research on the effects of beetroot in horses, but clearly if these findings were repeated, beetroot may well be a beneficial addition to horses’ diets. However, the story is not so straightforward and simple, as there are major differences in both the diet between humans and horses and also in the structure and function of their respective digestive tracts, which will influence the outcome. Firstly, as herbivores, a horse’s intake of nitrate from its diet is potentially much higher than that of a human. Typically an average diet in people will deliver 60-120mg of nitrate per day. The published improvement in exercise capacity was delivered following an acute intake of a concentrated beetroot shot of 70- 120mls providing about 300mg of nitrate about 2-2.5 hours before exercise. The nitrate content of typical ingredients that feature in the diet of a horse in training is shown in Table 3. It can immediately be seen that some components such as alfalfa have comparably high nitrate content. Given that horses in training may be consuming 5-8kg of forage per day, their nitrate intake compared to people may be much higher. However, at this stage we have no idea what the optimum intake of nitrate is for a horse given its greater bodyweight, blood volume, etc., and some species specific research would certainly be needed before any conclusions are drawn. Nitrate overload Some serious words of caution are also needed dampen our enthusiasm for nitrates, as this is a classic case of more is not always better. Excessive intake of nitrate can lead to a very high circulating level of nitrite, which can induce toxic effects such as methemoglobinemia. In this toxic state, the high nitrite oxidises the iron that forms part of the haemoglobin molecule in blood to form methaemoglobin, which is unable to carry oxygen. This is a clear disadvantage to horses in training. It is the bacteria that reside within the digestive tract that mediate the conversion of dietary nitrate to nitrite. In humans, babies are more susceptible to methemoglobinemia (blue baby syndrome) and adults are not normally at risk except where nitrate intake is exceptionally high. In contrast, ruminants and horses have a well developed fermentation chamber with bacteria capable of converting nitrate to nitrite. Horses, however, have a lower risk of nitrate intoxication than ruminants, as the conversion of nitrate to nitrite is reportedly lower (25%) and the hindgut is anatomically located after the main site of nitrate absorption (stomach and small intestine). Care should be taken to avoid cereals or forage that has been very heavily dressed with nitrogenous fertilisers. Some weeds such as Johnson grass, pigweeds, Jimson weed, Fireweed, and lamb’s quarter can accumulate nitrates and the level is also affected by environment including weather. Despite these potential negative issues, establishing the optimal nitrate intake for horses in training is an exciting challenge but one that requires a significant level of fundamental research. Beetroot may yet offer a new and exciting feed ingredient for horses in training and I will certainly be looking out for the beetroot story in humans to unfold in order to assess its potential application for horses.

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NUTRITIONWebmaster31 August 2012Beetroot, Digestion, Feeding Horses, EUT39
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