Race Horses

Challenges Race Horses Face

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Metabolism and Energy Production in Race Horses

Race Horses are extraordinary athletes and can perform physical abilities (running) that exceed most other animals of a similar size. The superior athletic ability of the horse is attributed to the horse’s high aerobic capacity, large intramuscular stores of energy, an ability to increase the oxygen carrying capacity of the blood, the efficiency of their gate and their ability to thermo- regulate and keep themselves cool when exercising. This article describes how metabolism and energy storage are achieved in the horse.

Following feeding, horses digest food into its different components. Carbohydrates (barley, oats etc.) are broken down into simple sugars such as glucose. Proteins are broken down into their individual amino acids (building blocks of proteins). Fats are broken down to fatty acids, some fatty acids are called polyunsaturated fatty acids (PUFAs).

After feeding of a horse, the rise in blood sugar initiates insulin release from the pancreas. Insulin allows glucose to leave the bloodstream and enter muscle or adipose (fat) tissue (among other body tissues), thereby returning blood glucose concentrations to baseline. Fibre (e.g., forages such as hay and pasture) are fermented by the good bacteria in the large intestine to produce volatile fatty acids (VFAs), namely acetate, propionate, and butyrate. Once absorbed, propionate is converted to glucose in the liver, while butyrate is converted to acetate. Acetate can then be metabolized to ATP by a variety of tissues or can be incorporated into fat synthesis.

Once inside cells the glucose can either be broken down, which results in the creation of ATP. ATP is the energy or “battery” of the body and enables muscles to contract. When at rest, excess levels of glucose are stored as glycogen (chains containing many thousand glucose molecules) for use during exercise.

Ninety percent of the body’s glycogen stores are in muscle and 10% are in the liver. When glycogen stores have run out the body then starts to metabolise fat to create energy and when fat reserves have been used up the body starts to metabolise protein to create energy.

During horse fasting, as blood glucose concentrations decline, a hormone called glucagon is released from the pancreas. Glucagon promotes the breakdown of glycogen stores in the liver to increase the blood glucose levels which can then be used for energy generation is whichever tissues require it. Glucagon also releases fats from fat stores, so fat can be used as an energy source. PUFAs are an excellent source of energy when they are oxidised. Finally, amino acids can be broken down to provide energy or glucose. Breakdown of protein and amino acids is the last resort and least preferred form of energy production, because it is not very energy efficient and produces ammonia in the process, which than must be detoxified to urea in the liver and excreted in the urine. The metabolism of protein to create energy results in loss of muscle mass and power and is therefore not desirable.

During horse exercise a hormone called adrenaline (the fight or flight hormone) is released into the circulation from the adrenal gland. Adrenalin releases free fatty acids from fat tissue, so that skeletal muscle can use them as fuel. Adrenaline also initiates the metabolism of skeletal muscle glycogen stores to glucose for energy (ATP) production. At all levels of work intensity, both carbohydrate (muscle glycogen, blood glucose) and fat are made available as fuels to the muscle. However, at lower levels of work intensity, proportionally more energy is derived from fat oxidation. At higher levels of intensity, more energy is derived from carbohydrate metabolism. Protein and amino acids can be used for energy sources during exercise, though as mentioned above their overall contribution to fuel production is minimal. Once glycogen stores become depleted fatigue and a decline in performance occur.

Depending on equestrian discipline and level of competition, the horse’s diet can be adjusted to maximise preferential feed reserves.  Endurance racing horses would require a higher fat diet to help increase the fatty acid stores that will be the main source of energy used during training and competition. On the other hand, the racehorse, while still using fatty acids to train, also needs higher levels of glycogen during a race over a few furlongs. The event horse and dressage horse have requirements that are somewhere between those of a race horse and those of an endurance horse.

Breakdown of glycogen;

In the presence of sufficient amounts of oxygen, adrenaline causes the breakdown of glycogen into glucose and glucose is then broken down to pyruvate and in the process ATP, carbon dioxide (CO2) and water (H20) are produced. The ATP is used for muscle contraction, the CO2 is removed in the lungs and the H20 is removed in the urine or sweat. If there is insufficient oxygen available to support aerobic metabolism, then glycogen is broken down to glucose and glucose is broken down to lactic acid. The lactic acid is then removed to the liver to be further broken down to glucose. If the rate of production of lactic acid in muscles is greater than the rate at which it can be cleared, pain and burning and a decline in performance occur. Glucose breakdown and lactic acid production are good for speed, but limit distance. Horses that produce the most lactic acid are almost always the fastest e.g. the polo pony or the 5-furlong sprinter. By comparison, the endurance horse produces very little lactic acid, even when exercising a maximum speed to fatigue. Similarly, whilst the 5-furlong Thoroughbred sprinter may have a blood lactate of 30 mmol/l after a race, it may be hard to push the blood lactate concentration of an elite 100-mile endurance horse above 5 mmol/l, even at a flat-out gallop. The difference, the endurance horse may be able to go for 100 miles at 10mph, but will come in way behind the 5 furlong sprinter and vice versa.

Aerobic metabolism is approximately 18 times more efficient than anaerobic metabolism. Consequently, training increases the aerobic capacity of horses, which is the time it takes for energy production to switch from aerobic to anaerobic.


Following digestion and absorption, amino acids are used to make protein, a key component of all tissues, but especially the muscle in an athletic horse. Muscle protein synthesis is activated by amino acids, insulin, certain hormones and by exercise stimuli. The greatest rates of muscle protein synthesis happen during growth, and rates decline as the animal ages. Dietary amino acids that are provided in greater quantities than can be used to make protein are degraded by the body, and the resulting ammonia is converted to urea (a nitrogen-containing molecule) and excreted in the urine. The conversion of ammonia to urea puts considerable “metabolic stress” on the liver.

Dietary modification and supplementation to support performance

Depending on the type of equestrian activity being undertaken there are several ways in which dietary modification and the use of nutritional supplements can support energy production and storage and clearance in horses. The balance between aerobic and anaerobic metabolism depends on the intensity of the exercise. The endurance horse typically travels at speeds (trotting and light canter) that can be maintained almost entirely by aerobic metabolism. On the other hand, all-out sprinting (e.g. Thoroughbred racing) and other forms of heavy exercise, such as the cross-country test in a three-day event, involve a substantial amount of anaerobic metabolism, with accumulation of lactic acid in muscle and blood.


Challenges Races Horses Face:


CHALLENGE: Increased metabolic rate and energy requirements

The metabolism of a horse is such that the metabolic rate can increase from very low at rest to hundreds of times greater at maximal exercise. The liver will turn lactic acid, fatty acids and amino acids into glucose through a variety of different enzymatic reactions. To support such a high requirement for nutrients during exercise the liver must increase its metabolic rate greatly. In increasing the metabolic rate, greater stress is placed on the liver cells, they must metabolise and clear carbohydrates and fat in greater quantities and at greater speeds, they have to break down lactic acid and turn it back into glucose, the have to clear the toxic products of metabolism e.g. ammonia and the liver cells are very susceptible to oxidative damage as a result of the free radicles that are produced during metabolism.


contains a variety of vitamins and amino acids to help the liver to use fats to create energy and glucose and to clear the products of fat metabolism from the liver so that fat does not build up in the liver. LIVERPAK 100 also contains several plant-derived ingredients (rosemary, artichoke and milk thistle) as well as vitamins C and E to protect the liver against damage from the biproducts of metabolism. LIVERPAK 100 also contains propylene glycol which can be readily converted to glucose and used as an immediate energy source.

The milk thistle in LIVERPAK 100 helps to protect liver cells (hepatocytes) against oxidation and inflammation. Rosemary is an excellent anti-oxidant and artichoke leaf extract promotes the clearance of bile from the liver and prevents the build up of fats in the liver. LIVERPAK 100 also contains methionine, choline, carnitine and inositol. Choline and methionine are two key substances that promote fat metabolism especially in the liver. Choline and methionine requirements can spare each other, such that supplementation with one reduces the requirement for the other and vice versa. Methionine is used for the generation of S-adenosylmethionine (SAMe), which in turn is used for the synthesis of choline. SAMe is a very powerful hepato-protectant and protects the liver cells against damage from toxic metabolites.  Methionine is also involved in many pathways including the synthesis of phospholipids, carnitine and creatine. The carnitine contained in LIVERPAK100 is required for the transport of long-chain fatty acids into cells so that the fats can be oxidised and used for energy production.  The inositol in LIVERPAK100 is included to assist with generation of energy from fats.

The horse’s diet can be modified to increase carbohydrate and there for muscle glycogen stores in race horses. LACTESE PLUS acts in a similar way to insulin and promotes glucose uptake and storage in muscle cells. The water-soluble B VITAMINS all play essential roles in the breakdown and metabolism of food as well as various biochemical processes in the body. The B vitamins are also excellent at stimulating appetite and promoting feed intake which is imperative for the equine athlete.


CHALLENGE: Muscle damage and fatigue

Two types of fatigue have been recognised. The first, horse muscle fatigue occurs when muscles run out of energy sources and can no longer create the ATP that is required for them to contract.  ENERGY 1000 contains ATP and DMG, supporting energy release for the racehorse. The second is central fatigue whereby an increase in serotonin levels in the brain contribute to fatigue. Muscles rely on glycogen as a source of energy, and glycogen reserves can be spared by increasing the fat content of muscle so that the fat metabolism spares the glycogen reserves thus enabling muscles to work for longer before fatiguing.

High intensity bursts or long duration exercise results in significant damage to muscle cells. Energy production from metabolism results in free radicles which damage muscle cells. Prolonged exercise results in the depletion of enzymes and vitamins that scavenge and remove these damaging free radicals and oxidation of the fats in the cell walls occurs leading to cell rupture and death. Several cells can be affected including red blood cells and muscle cells.  To further compound the matter, when horses deplete their energy reserves of glycogen and fat in the muscles they start to break down the muscle tissue to use as an energy source. Muscles are composed of amino acids and one third of equine muscle in composed of the branch chain amino acids (BCAA), leucine, isoleucine and valine. Leucine, isoleucine and valine are essential amino acids and cannot be synthesised by the horse and must therefore be supplied in the diet.


BCAA Box & SyringeBCAA contains the three essential BCAAs, leucine, isoleucine and valine to support muscle recovery following exercise. Supplementation with BCAA has been demonstrated to increase the levels of these amino acids in muscle following strenuous exercise. The administration of leucine has been shown to reduce the concentration of amino acids in the blood following exercise, indicating a beneficial reduction in protein breakdown. Additionally, BCAA also contains rosemary a powerful antioxidant to protect muscle cells against oxidative damage and seaweed which acts as a pre-biotic to support intestinal health. Leucine also has a powerful insulin like effect and promotes the uptake of glucose into cells. Several studies have demonstrated that during endurance events horses metabolise a large amount of BCAA to produce energy. BCAA and another amino acid called tryptophan use the same transport system for entering the brain and it has been suggested that as blood and muscle levels of BCAA fall, more tryptophan can enter the brain. Tryptophan is converted to serotonin and increasing levels of brain serotonin may contribute to central fatigue.

AMINOBOOST contains all the essential amino acids required by horses. It may be especially important to supplement amino acids in horses who are poor eaters or who have variable appetites, as many horses do when they are travelling and away from their familiar environment. The functions of amino acids are diverse and insufficient levels of one, may impact levels of another. Supplementation with amino acids in the immediate recovery period has been shown to reduce muscle breakdown and promote recovery following strenuous exercise. Recent studies show that in addition to muscle breakdown, a significant number of amino acids are lost in equine sweat. AMINOBOOST contains creatine, carnitine and ϒ-oryzanol. Creatine is an amino acid that is naturally present in the diet and muscle. Creatine is an important source of energy for aerobic metabolism and has been demonstrated to improve the aerobic capacity of horses following long term supplementation. Creatinine is turned into creatinine phosphate which provides energy for muscle contraction. Carnitine is a component of enzymes that is involved in the utilisation of fatty acids as an energy source. Supplementation with carnitine increases utilisation of fatty acids as an energy source and this spares glycogen and could improve aerobic capacity. ϒ- oryzanol is derived from brown rice bran and has been shown to have a powerful anti-oxidant effect which may protect muscle cells against free radicle damage.


CHALLENGE: Increased antioxidant requirements:

Burst of strenuous anaerobic exercise result in oxidative damage to all cells but especially muscle cells and the cells of the immune system which are particularly susceptible to oxidative damage because of the high fat content of their cell walls. Also, increase requirements for energy place metabolic stress on the liver which must manufacture glucose as a source of energy, either from stored glycogen, fats or proteins. The liver also experiences oxidative stress. The liver also must process and excrete the products of metabolism such as urea and the contents of damaged muscle cells.  Vitamin E and selenium are powerful antioxidants. Vitamin E which is fat soluble is essential for normal nerve and muscle function and is stored in fat. Fit racehorses are often lean and do not have large reserves of fat to store vitamin E.


RACING E contains vitamins E & C and Selenium that helps to protect cells against oxidative damage that 
occurs when fats in cell walls become oxidised (lipid peroxidation) and cells walls then become leaky or rupture. RACING E also contains methionine, which helps to support the liver in metabolism and lysine which is an essential amino acid required for muscle repair. Racing E is a powder for long term use in horses in training and Power E is a paste which as well as containing vitamin E also contains rosemary another powerful antioxidant. POWER E including Carnitine is also available and can be used in the immediate period following strenuous exercise where antioxidant damage is likely to be especially high. The L-Carnitine will also help to release more energy during strenuous exercise.   It carries long chain fatty acids into mitochondria, where they are converted into energy for muscle contraction.


CHALLENGE: Lactic acid production:

During high intensity exercise, cells in the body and especially muscle do not receive oxygen in sufficient amounts to meet their metabolic demands and consequently metabolism switches from aerobic (in the presence of oxygen) to anaerobic (in the absence of oxygen). In aerobic metabolism glucose is combined with oxygen to release energy and carbon dioxide and water. In anaerobic metabolism glucose is converted to lactic acid in the absence of oxygen and it is only during recovery from exercise that lactic acid is cleared from the body by combining lactic acid with oxygen to produce carbon dioxide and water. A build-up of lactic acid in muscles, leads to a burning sensation, painful muscles and lactic acid in the blood.


LACTESE PLUS contains lipoic acid which is involved in energy metabolism of proteins, carbohydrates and fats. Lipoic acid has physiological functions in blood glucose utilisation and can scavenge several free radicals. Lipoic acid which has been demonstrated to decrease post-exercise lactic acid concentrations in horse and lipoic acid plays a central role in antioxidant production which helps to protect muscles against oxidative damage. Lipoic acid is an important co-enzyme of pyruvate dehydrogenase and facilitates the removal of lactic acid from the muscle and circulation to the liver. In the liver the lactic acid is then turned into glucose via the lactic acid cycle and the glucose is returned to the cells to be used as a source of energy.

LACTESE PLUS contains Thiamine (vitamin B1), Riboflavin (vitamin B2), Pantothenic acid and nicotinic acid which are all essential for the metabolism of carbohydrates, fats and proteins.


CHALLENGE: Increased risk of gastric ulceration:

It is estimated that as many as 50-90% of horses in training may experience gastric ulcers. In the absence of access to continuous grazing, horses are more prone to the development of gastric and duodenal ulcers. Gastric ulcers arise because of the insufficient buffering of stomach acid with bicarbonate in saliva that occurs between feeds. Clinical signs include, poor appetite, poor performance, signs of abdominal pain or colic, teeth grinding and changes in temperament. Management measures such as increasing access to food, feeding little and often and decreasing stress factors are important in managing horses with ulcers.


GASTROFEN offers a non-pharmaceutical solution to assist horses with gastric ulcers. GASTROFEN contains a seaweed extract pre-biotic to encourage the growth of good intestinal bacteria, a probiotic containing beneficial intestinal bacteria, threonine to assist with mucous production and the protection of the intestinal wall and vitamin E which acts as an anti-oxidant for damaged intestinal cells.


CHALLENGE: Intestinal Dysbiosis

Intestinal dysbiosis refers to an imbalance between good bacteria and bad bacteria in the intestine of the horse. A healthy population of good bacteria (called microflora) are required for the efficient digestion of food and the manufacture of short chain fatty acids such as propionate, acetate and butyrate that are converted to energy in the liver. A healthy intestinal microflora also synthesis many of the vitamins required for generating energy from carbohydrates, fats and proteins. A balanced and healthy microflora also stimulates the gastrointestinal immune system and prevents the adhesion of bad pathogenic bacteria to the intestinal wall. Sudden changes in diet from feeding grass to feeding of rapidly fermentable, high carbohydrate diets are common practices in the horse industry and have been associated with digestive and metabolic disorders that can impair the performance of horses. Abrupt changes in diet don’t allow sufficient time for the microflora to adapt to the high carbohydrate diet and thus undigested carbohydrates can enter the large intestine in large quantities leading to hind gut acidosis and predisposing horses to the development of acute or subacute laminitis or colitis. Dysbiosis also leads to suboptimal digestion of carbohydrates and thus reduced energy derived from food. Travelling can also cause intestinal dysbiosis in horses, which has been reported after just two hours of transport.


PRO-BIO EQUINE contains a probiotic yeast called Saccharomyces and in horses fed high-starch diets, live yeast supplementation appeared to limit the extent of undesirable changes in the intestinal microbial population. Yeast probiotic has also been shown to benefit the intestinal microbial population after just two hours of travelling. Saccharomyces has also been demonstrated to improve the digestibility of food in horses. PRO-BIO EQUINE also contains threonine which is broken down to form mucin which lines the digestive tract and protects it from damage from stomach acid, harmful bacteria and toxins. The B vitamins included in PRO-BIO EQUINE support the metabolism of carbohydrates, fats and proteins to produce energy and vitamins E and C are potent antioxidants which help to protect the intestinal wall from damage caused by bad bacteria in cases of intestinal dysbiosis. Many horses go off their feed or have interrupted feeding patterns while travelling or racing the B vitamins in PRO-BIO EQUINE help to stimulate appetite so that good tissue levels of carbohydrates, fats and proteins are maintained prior to racing.


CHALLENGE: Increased risk of respiratory disease

Racehorses are at a greater risk of developing respiratory diseases. In addition to infectious diseases, the management of racehorses is such that normal airway mucous clearance is impaired because horses aren’t grazing with their heads down for prolonged periods. Furthermore, long periods of transport to and from race tracks subject horses to increased levels of ammonia in the environment and a raised head position when tied. Horses are also in close contact in a confined space when travelling which increases the risk of infectious disease. Respiratory tract infection is more likely to occur on longer journeys than short. Upper respiratory tract infection that cause a watery discharge from the nose are less common than lower respiratory tract infections that result in increased mucous and inflammatory cells in the trachea (windpipe). The incidence of inflammatory lower airway disease (IAD) is high in race training yards and especially in young horses. One study reported a mean monthly prevalence of around 12% and an incidence of around 10 cases/100 horses/month. The mean duration of each incident is around 8 weeks, and the disease is often recurrent in individuals. The monthly prevalence and incidence of signs of upper respiratory disease are around 5% and 5 cases/100 horses/month indicating that it is less common. While vaccination is a requirement to enter race track facilities many of the bacteria isolated from cases of IAD are not included in the “flu” vaccination therefore vaccination does not protect the horses against these infections. Bacterial and mycoplasma infections are usually more common in younger horses, but an degree of immunity is established as horses get older.  Furthermore, vaccination does not prevent exposure to bacteria and viruses, but it does reduce the incidence and severity of the disease, consequently many horses that have been exposed may not show overt signs of respiratory disease but may be showing signs of poor performance.

Exercise induced pulmonary haemorrhage (EIPH) is a common finding in racehorses. In one epidemiological study the incidence of EIPH varies between trainers but increases with age, season (from winter to autumn months) and the presence of inflammatory airway disease and fungal particles.


respiron equineBoth IAD and EIPH significantly impact performance. RESPIRON contains Echinacea, seaweed, oregano, garlic, rosemary and vitamin C. Echinacea is a potent immune stimulator and supports the local immune system in the horses’ airway to fight infectious diseases. Vitamin C and rosemary are both are excellent antioxidants and it has been demonstrated that vitamin C is required in additional amounts during inflammation. RESPIRON also contains garlic and oregano. Garlic and oregano have antibacterial and antiviral effects and garlic is also a mucolytic which thins mucus, so it can be more easily cleared from the airways.

Exercise induced pulmonary haemorrhage (EIPH) occurs because of stress failure of the pulmonary capillaries resulting from excessive pressures across the wall of the capillary. This could be because of increased positive pressure in the capillary or decreased pressure in the lung alveoli. The incidence and severity of EIPH tends to increase with age. One of the consequences of EIPH is inflammation and increased mucous in the lung because of the presence of blood and severe EIPH can significantly reduce performance. HAEMOFORTE contains bioflavonoids (citrus sinensis) which help to increase the strength of the capillary wall.  Bioflavonoids also enhance or potentiate the antioxidant effect of vitamin C. Rosemary is included in HAEMOFORTE and is also an important antioxidant in limiting the damage or inflammation in the lung caused by the haemorrhage. HAEMOFORTE contains vitamin K3 (menadione) which plays a role in blood clotting. Although impaired blood clotting is not the reason for EIPH to occur, in situations where there may be reduced levels of vitamin K3 (some moulds counteract the effects of vitamin K3), supplementation may be beneficial.