utrition plays a major role in optimising performance in the event horse. Speed, strength, stamina, temperament along with delayed onset of fatigue and improved post exercise recovery times can all be directly influenced by diet.
The main component of any horse’s diet should be forage. Forage intake should be at least 1.5% of bodyweight per day ie 7.5 kg a day for a 500 kg horse, with an absolute minimum of 1% BW, to ensure good intestinal health. In addition, for the performance horse, each kilogram of forage holds 6-8 kg of water and electrolytes in the gut. This represents a ‘reservoir’ that can be drawn on as body fluid levels drop during sweating.
Many riders reduce or remove forage before the cross-country phase. Removing forage 3 to 5 hours prior to hard exercise may be advantageous due to a reduction in non functional gut weight and in cardiovascular load during exercise. However several studies have found that feeding small amounts of hay prior to exercise was not associated with poor or reduced performance.
On the other hand, feeding concentrates 3 to 5 hours before hard work is recommended, thus allowing ample time for metabolites to return to resting values following meal consumption and providing adequate fuel reserves for work.
Feeding forage and grain based concentrate two hours following an intense or long duration bout of exercise is essential in restoring glycogen pools in the liver and muscle.
Meeting Energy Demands
The single factor most likely to affect performance is lack of energy, due to either inadequate fitness training for the level of competition or dietary limitations. The amount of energy required depends on: the type, speed and amount of work, condition of the horse and skill of the rider and the environmental conditions.
Event horses obtain energy in two ways:
1. During low intensity work, muscles convert glucose to energy using oxygen – this is called aerobic work. Aerobic work can be sustained for long periods, such as the cross country phase in eventing.
2. During high intensity exercise, the muscles use energy so quickly that aerobic energy supply is exceeded and glucose must be converted to energy without using oxygen. This is called anaerobic work. Anaerobic work can only be sustained for a very short period and results in lactic acid production. Anaerobic energy serves to ‘top up’ aerobic supply.
As a rule of thumb in the fit horse, anaerobic work begins to kick in when speed reaches approximately 10 metres per second and heart rate climbs to around 160 to 180 beats per minute.
Delaying onset to fatigue
During low-intensity, prolonged work (ie aerobic), fatigue occurs due to depletion of energy and overheating. In high intensity work (anaerobic), fatigue is caused by lactic acid build up and energy depletion. Feeding to increase aerobic and anaerobic energy can delay the onset of fatigue. Falling glucose levels, rising lactic acid levels and heat stress all reduce muscle function. However, certain feeding strategies can increase blood and muscle glucose and reduce heat production.
Exercising horses need adequate amounts of energy in order to maintain bodyweight while having sufficient energy to perform to the level of work asked of them. Energy can be obtained from fibre, starch and oil. High intake of starch rich or high carbohydrate concentrates can potentially cause metabolic problems such as gastric ulcers or tying up. Choose a feed that has been specifically formulated for the performance horse that is high in both oils and super fibres and low in starch. Energy requirements will be met while metabolic disorders can be kept to a minimum.
Several studies have shown muscle glucose can be increased by dietary manipulation. When the amount of fermentable polysaccharides (eg raw grains) to the large intestine is minimised, glucose availability is maximised for the performance horse. Ideally choose a concentrate that incorporates a processed or a cooked form of starch eg steam flaked grains. Feeds containing cooked cerealsare recommended for horses that require more than 3 kg of concentrate per day, those prone to ‘tying up’ and to reduce heat load.
To optimise on digestion and reduce the risk of digestive disorders keep meals to 2.5 kg or less. Most high level performance horses will need at least 5 kg of concentrate per day but this will depend largely on the individual. If you find that your horse is maintaining sufficient body condition and you are having to feed below the recommended feeding guidelines it may be advisable to top dress with a performance balancer. Performance balancers provide the key nutrients essential to performance without the excess calories, aiding in reducing onset of fatigue and improving post exercise recovery times.
Oils & Fats
High oil feeds offers enormous benefits for temperament (critical for the dressage phase), heat load and performance. Oil provides a cool and steady supply of energy – allowing the horse to preserve blood glucose levels. This ‘glucose-sparing’ effect delays the onset of fatigue, so that although horses cannot increase their top speed, they can maintain it for longer. Oils are also an excellent way to increase the weight of a horse. They are primarily digested in the small intestine and contain approximately 2-3 times more energy than the same weight of raw grain. Introduce the oil to the diet gradually over a 3-6 week period. Because of the abundance of Omega 6 in diets, it is important to provide an Omega 3 supplement. A recent veterinary review article indicated that Omega 3 oils may be beneficial for treating colitis and enteritis, and in preventing arthritis, laminitis, small airway disease associated with stabling and dermatitis. All oils provide energy, only Omega 3 oils reduce inflammation. Cod liver oil and flaxseed/linseed oils are high in Omega 3.
Protein is both an over emphasised and misunderstood nutrient. Although it is an essential element of the high level performance horse’s diet, its quality is often overlooked and the focus has been more on its quantity. Excess protein in the diet of the performance horse will be broken down and utilised as an energy source providing both an inefficient and expensive energy pathway. This process leads to excess urine production, excess ammonia in the stable, inefficient heat removal and irritability.
Horses which are travelling, working in hot or humid conditions and in hard training, may require additional electrolytes. The effects of dehydration can cause tying up, longer post exercise recovery times, increased onset to fatigue and muscular problems. Supplementation of electrolytes may be required according to workload and ambient conditions.
Hard training and competing cause muscle damage due to lactic acid and/or over exertion. Intense exercise is a catabolic process. Supplying the correct balance of carbohydrate, specific essential amino acids and anti-oxidants after an intense workout, the catabolic state can be switched to an anabolic (rebuilding of tissue) state, enabling muscles to recover and respond more quickly to training and competition.
In feeding the event horse a balanced diet is key in reducing onset to fatigue and improving post exercise recovery while the challenge of meeting energy demands for both stamina and speed and keeping an even temperament can be met through the use of alternative energy sources, such as fibres and oils. Using cooked wholesome ingredients will ensure optimised digestion and good feed utilisation and will minimise digestive related disorders. Supplements such as oils, chaffs and electrolytes will always play an important role in the diet of the high level performance horse.
Dr. Jenny H Stewart BVSc BSc PhD MRCVS Dip BEP AAIM