Small but mighty - the role of antioxidants for horses in training

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Small but mighty The role of antioxidants for horses in trainingAntioxidants are substances that slow down damage to organisms created by the presence of oxygen. The need for antioxidants is always there, in all species, increasing as exercise intensity and duration increase. Is there merit in specifically supplementing antioxidants to enhance performance? The nature of antioxidantsThere are many forms of antioxidants naturally present within the body and supplied through the diet. One key feature of antioxidants is that they are ‘team players’. No one antioxidant alone can maintain the system, and some will only function in the presence of another antioxidant. The role of an antioxidant is to keep reactive oxygen species (ROS) or free-radicals created in the presence of oxygen at an optimum level. Oxygen is required for life, it is always present, but as an element, it is highly reactive and so can also have an adverse effect on the body. The reactivity of oxygen in the body produces ROS which cause damage to cellular components such as DNA, proteins and lipids of cell membranes. Some ROS also have useful cellular functions, and so the purpose of antioxidants is not to eliminate ROS altogether but to maintain a healthy balance. In general, antioxidants operate in two ways: either preventing the formation of an ROS or removing it before it can cause damage to a cell component.Sources of antioxidantsThere are multiple sources of antioxidants including vitamins, enzymes and nutrient derivatives. Other nutrients such as minerals, whilst not having antioxidant properties, are also involved as their presence is required for the functioning of antioxidant enzymes. Two key examples are zinc and selenium.Antioxidant ExamplesVitamin CVitamin ESuperoxide dismutase Glutathione peroxidaseLipoic acidGlutathioneUbiquinol (co-enyzme Q10)Oxidative stress Photo: horse exercising?As with many body systems, the ideal healthy balance can often go awry. When the level of ROS present overwhelms the capacity of antioxidants present, the body experiences oxidative stress. There are three main reasons for a horse in training experiencing oxidative stress:Increased exposure to oxidants from the environmentAn imbalance or shortage in supply of antioxidantsIncreased production of ROS within the body from increased oxygen metabolism during exerciseOxidative stress is of concern as it can exaggerate inflammatory response and may be detrimental to the normal healing of affected tissues. Oxidative stress during strenuous exercise, such as galloping or endurance, is typically associated with muscle membrane leakage and microtrauma to the muscle. Oxidative stress is now understood to play a role in previously unexplained poor performance.Dietary antioxidants photo: horse eating?Given the demands of training and the regularity of intense exercise and racing itself, the use of dietary antioxidants is an important consideration. As antioxidants are generally best considered as a cocktail, it is necessary to give consideration to provision of nutrients and their derivatives across the total daily diet. The majority of racing feeds will be formulated to provide a good cocktail of basic antioxidants or their supporting minerals. All feeds will contain vitamin E, selenium and zinc for example. Some, but not all, feeds will also provide vitamin C. The source of these nutrients may also differ; for example, some feeds will contain chelated zinc or organic selenium, which offer improved availability. The source of vitamin E will also vary—the majority being provided as synthetic vitamin E; but some will include natural sources of vitamin E, which is more effective. Once a good base diet is in place, consideration for strategic use of individual antioxidants may then be warranted to further enhance the capacity of the body to mitigate the effects of ROS on the muscle. Three popular and commonly used antioxidants are vitamin E, vitamin C and more recently coenzyme Q10.Vitamin EAs a lipid-soluble antioxidant, vitamin E provides defence against ROS in cells, playing an important role in maintaining integrity of cell membranes. Vitamin E is the most commonly supplemented antioxidant. There are established recommended daily intakes for vitamin E, typically 1000 IU per day for a horse in training; however, further supplementation beyond the basic nutritional requirement can yield benefits. Modern race horse feeds are well fortified—the majority providing upwards of 300 IU/kg, resulting in an average daily intake of over 2000 IU/day.Intakes of above the base rate have been investigated for their effect on CK (creatine kinase) and AST (aspartate aminotransferase)—two markers of muscle damage. One such study used endurance horses whereby intakes ranged from 1150 IU up to 4750 IU per day. Elevated intakes of vitamin E correlated with lower levels of CK and AST suggest that vitamin E can affect muscle membrane permeability and injury to muscle during exercise. As a guide to improving antioxidant capacity, an intake of up to 5000 IU per day would be appropriate for a horse in training. Vitamin E intake is influenced by the level of fats fed in the diet; and where additional oils are added, further vitamin intake E is required, as vitamin E will be utilised in stabilising the oil itself. Fats fed in a dry format, such as extruded rice bran, are normally fortified with vitamin E for this reason and do not require further supplementation. Vitamin E is available in feeds and supplements in two forms: synthetic or natural. The natural form, d-alpha-tocopherol, is made up of a single isomer (chemical unit). The synthetic form, dl-alpha-tocopherol, is made up of eight different isomers—only one of which is molecularly the equivalent of natural vitamin E. The dose rate required to increase serum vitamin E levels in horses is lower for natural E than synthetic vitamin E. Effect of feeding 5000 IU per day of a synthetic or natural vitamin E form (Nano-E) on serum vitamin EImage Source Kentucky Equine ResearchThe increased bioavailability of natural vitamin E has led to further research in comparing this source against synthetic vitamin E for efficacy against oxidative stress and physical gait changes. The study used 3 diets: a control diet with the standard recommended intake of 1000 IU/day provided by synthetic vitamin E; a higher intake synthetic vitamin E diet of 4000 IU/day; and a high intake of natural vitamin E at 4000 IU/day. The study lasted for six weeks and measured serum levels of vitamin E at various time points along with markers of oxidative stress, CK and AST levels, and gait analysis.The key findings:All diets increased serum vitamin E over time; however, the increase was not significant in the diet, providing only 1000 IU/day of synthetic vitamin E. The greatest difference in serum vitamin E was seen in the natural vitamin E diet where levels increased by 77.25% from day one to the last time point.Oxidative stress was measured through multiple tests including oxidation of lipids (TBARS). Horses supplemented with natural E had lower levels of lipid oxidation markers than both synthetically supplemented horses at the second exercise test, which occurred after six weeks of fitness training.AST levels were lower within the two hours post exercise of natural E supplemented horses compared to synthetic vitamin E horses; however, by 24 hours, the difference was no longer significant. There was no noted significant effect on CK. Gait analysis before and after exercise showed better movement of horses that were supplemented with natural vitamin E. These horses experienced less of a reduction in their stride duration post exercise, potentially indicating less muscle soreness due to less oxidative stress.As vitamin E is well proven to be an effective antioxidant, it may be tempting to think that ‘more is better’; however, as with all nutrients, there is a safety limit to consider. Current research indicates that supplementing at 10 times the base level—an intake of 10,000 IU/day—may result in poor bone mineralisation and impair beta-carotene (vitamin A) absorption. An intake of 4000-5000 IU/day based on the research above and other studies would appear effective whilst also being well below the presumed safety limit. Vitamin COrdinarily horses can manufacture adequate vitamin C within the body, unlike humans that require direct supplementation. Additional vitamin C is required and often recommended when the body is challenged through disease or periods of stress. Research has shown vitamin C is needed for horses with recurrent airway obstruction, horses following colic surgery and foals during weaning when stalled. The variety of situations in which vitamin C requirements increases is broad, and the demands and stressors of training make vitamin C an attractive supplement.Vitamin C is water soluble and has the advantage of being able to work both inside and outside the cell to combat free-radical damage. Whilst being an antioxidant in its own right, it also has another significant benefit relating to vitamin E. Vitamin C is somewhat ‘self-sacrificing’ and can regenerate spent Vitamin E, reviving it to an active antioxidant. The combination of vitamins E and C is therefore a common and well-established cocktail in certain feeds and antioxidant supplements. The benefits of combined supplementation have been documented in endurance horses racing 80km and also in polo ponies. What is important to note, is that when monitoring plasma levels of vitamin E and C within the polo ponies group, that supplementation was only successful in elevating serum levels in the hard working group when both E and C were supplemented. Those in hard work supplemented with vitamin E only did not see the same benefits. There is no set recommended daily intake for vitamin C as the body can synthesise enough for daily functions. The level of supplementation of vitamin C and the point at which it becomes effective will be in part dependent on other antioxidants present in the diet. Vitamin C is not easily absorbed, and to change blood ascorbate levels requires an intake of at least three grams per day. Research into racing endurance horses was effective at 7g per day fed in combination with 5000 IUof vitamin E. As a guide, based on research into various conditions benefiting from vitamin C, an intake of 5-10g per day would be suitable for a horse in training. Vitamin C supplementation may impact the body’s ability to naturally synthesise vitamin C, and so any period of supplementation of greater than 10 days should not be abruptly halted. If choosing to discontinue high intakes of vitamin C, the feed or supplement should be gradually transitioned downwards.Coenzyme Q10 (ubiquinone)Coenzyme Q10, also known as ubiquinone, is an effective antioxidant and has the ability to regenerate both vitamin E and vitamin C, making it an interesting addition to the diet. Unlike vitamin E and vitamin C, coenzyme Q10 is not a vitamin. It is synthesised in all body tissues, and the name ubiquinol given to this substance in 1975, is derived from the adjective ubiquitous—a nod to the compound’s widespread distribution in nature. Horses, when compared to humans, are naturally lower in coenzyme Q10 as measured in serum. Research in 2013 confirmed that supplementing with coenzyme Q10 could increase serum levels; in this particular study 800mg was given per day for 60 days. Further research looking at serum coenzyme Q10 following steady exercise or intense exercise (breezing) at dose rates of 1.9g per day, and 3.4g confirmed that supplementation raised serum profiles. Further to that confirmation, the serum levels post breezing were not as elevated, demonstrating that coenzyme Q10 was ‘spent’ during intense exercise periods. Coenzyme Q10 is the latest antioxidant to gain more attention and research specific to equines and is proving to be of interest in mitigating oxidative stress.More recently, a liquid form of coenzyme Q10 has been investigated by Kentucky Equine Research (KER) for its effects on a group of horses in training. Much like the conversation around vitamin E sources, the form of coenzyme Q10 also influences bioavailability with the liquid form being more available than the powdered form of crystallised ubiquinone. This study looked at energy production in skeletal muscle enzymes, showing an improvement when supplemented, and blood GGT levels. Gamma-glutamyl transferase (GGT) is an enzyme monitored in blood and is most commonly associated with liver damage; however, GGT is found in many body cells. Research is indicating a link with elevated GGT and poor performance of horses in training attributed to oxidative stress. GGT levels measured during the KER study of nano-Q10 showed that horses with higher serum coenzyme 10 had lower levels of GGT.Work in Ireland has also directly researched the effect in thoroughbreds, looking at a microactive form of Q10 and its effect on antioxidant enzyme presence in skeletal muscle. The most positive finding from this study was an increase in gene encoding of glutathione peroxidase isozymes. Glutathione peroxidase is a key enzyme in antioxidant defence systems. The study confirms that not only is coenzyme Q10 an antioxidant in its own right but that it can support defence systems through indirectly benefiting expression of other antioxidant enzymes. Coenzyme Q10 could perhaps be described as the ultimate team player when considering choosing an additional antioxidant to supplement. ConclusionThe use of a cocktail of dietary antioxidants is well warranted when considering an approach to reducing the effect of oxidative stress on muscles and in general recovery. It is important to understand what level and form of antioxidants are currently provided through your racing feed to establish the base daily intake and build from here upwards. The level of vitamin E, and possibly vitamin C, to consider supplementing will depend on the intake provided by the diet. Coenzyme Q10 is not found in racing feeds, is a straight addition to the diet and is certainly an excellent team player in terms of supporting regeneration of other key antioxidants. Reading ListCurley,C.E., Rooney,M.F., Griffin,M.E., Katz,L.M., Porter,R.K., Hill,E.W. (2018) Dietary supplementation with MicroActive Coenzyme Q10 increases expression of antioxidant genes in Thoroughbred skeletal muscle. Biochimica et Biophysica Acta (BBA) – Bioenergetics (1859) supplement, p45Fagan,M.M., Harris,P., Adams,A., Pzdro,R., Krotky,A., Call,J., Duberstein,K.J. (2020) Form of Vitamin E Supplementation Affects Oxidative and Inflammatory Response in Exercising Horses. Journal of Equine Veterinary Science (91)Geor,J. Harris,P. Coenen,M. (2013) Equine Applied and Clinincal Nutrition. China: ElsevierPagan, JD.(2006) Tocopherol form affects vitamin E. Feedstuffs 78 (2006)Sinatra,S.T., Stanley,N.J., Chopra,R.K., Bhagavan,H.N. (2014) Plasma Coenzyme Q10 and Tocopherols in Thoroughbred Race Horses: Effect of Coenzyme Q10 Supplementation and Exercise. Journal of Equine Veterinary Science (34) 2, p265-269

By Catherine Rudenko

Antioxidants are substances that slow down damage to organisms created by the presence of oxygen. The need for antioxidants is always there, in all species, increasing as exercise intensity and duration increase. Is there merit in specifically supplementing antioxidants to enhance performance?

• The nature of antioxidants

There are many forms of antioxidants naturally present within the body and supplied through the diet. One key feature of antioxidants is that they are “team players.” No one antioxidant alone can maintain the system, and some will only function in the presence of another antioxidant. The role of an antioxidant is to keep reactive oxygen species (ROS) or free-radicals created in the presence of oxygen at an optimum level. Oxygen is required for life; it is always present, but as an element, it is highly reactive and so can also have an adverse effect on the body. The reactivity of oxygen in the body produces ROS which cause damage to cellular components such as DNA, proteins and lipids of cell membranes. Some ROS also have useful cellular functions, and so the purpose of antioxidants is not to eliminate ROS altogether but to maintain a healthy balance. In general, antioxidants operate in two ways: either preventing the formation of an ROS or removing it before it can cause damage to a cell component.

• Sources of antioxidants

There are multiple sources of antioxidants including vitamins, enzymes and nutrient derivatives. Other nutrients such as minerals, whilst not having antioxidant properties, are also involved as their presence is required for the functioning of antioxidant enzymes. Two key examples are zinc and selenium.

Screenshot 2021-04-23 at 11.21.25.png

Oxidative stress

As with many body systems, the ideal healthy balance can often go awry. When the level of ROS present overwhelms the capacity of antioxidants present, the body experiences oxidative stress. There are three main reasons for a horse in training experiencing oxidative stress:

• Increased exposure to oxidants from the environment

• An imbalance or shortage in supply of antioxidants

• Increased production of ROS within the body from


100120_DERRINSTOWN STUD9 (1).jpg

increased oxygen metabolism during exercise Oxidative stress is of concern as it can exaggerate inflammatory response and may be detrimental to the normal healing of affected tissues. Oxidative stress during strenuous exercise, such as galloping or endurance, is typically associated with muscle membrane leakage and microtrauma to the muscle. Oxidative stress is now understood to play a role in previously unexplained poor performance. …

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