Horses involved in endurance riding require appropriate fitness training, careful management, and balanced nutrition to support stamina and recovery.

Endurance racing may involve horses covering up to 100 miles or 160 kilometres in a single day. This poses challenges with maintaining energy, hydration and soundness.

During intense training and competition, endurance horses can have 60% higher energy demands compared to horses at maintenance.

Meeting this demand with gut-friendly calorie sources is key to supporting health and well-being. Feeding high-quality forages, digestible fibre sources, and adding fat to the diet are great ways to meet the needs of endurance horses.

Heavily exercising horses of all disciplines are at higher risk of digestive issues such as gastric ulcers and hindgut acidosis.

You can reduce the risk of gut problems by feeding a low-grain, forage-based diet that satisfies your horse’s natural drive to consume high-fibre plant material. Limiting stress and supporting exercise recovery can also help keep your equine athlete healthy.

For help with optimizing your endurance horse’s feeding program, submit their information online to receive a free diet evaluation.

What is Endurance Riding?

The first endurance competition ever hosted was the Tevis Cup in 1955. This race is a 100 mile (160 km) long ride from Nevada to California completed in 24 hours.

Traditionally, the Tevis Cup was a relatively slow ride with an average speed of 8.4 km/hr (5.2 mph). However, recent winners of the World Equestrian Games 100-mile ride in Kentucky have competed with an average speed of over 20 km/hr (12.4 mph).

Most breeds can be used for endurance races. Arabian or Arabian crosses are best adapted to low-intensity long-distance exercise due to their muscle fibre composition and oxidative capacity. [1]

Physiology of Endurance Racing

Endurance refers to the physical and mental capacity to withstand fatigue. Endurance racing is a test of aerobic fitness as these horses cover long distances at a trot, interspersed by some walk and canter.

Endurance horses are generally able to supply enough oxygen to their tissues to support aerobic metabolism throughout the race. In comparison, horses in sprinting disciplines rely on anaerobic processes that can make energy without oxygen.

Aerobic metabolism produces less lactic acid compared to anaerobic metabolism and horses are therefore able to sustain this level of exercise for prolonged periods of time. [1]

However, completing an endurance race is a challenge as horses must be trained to persevere over long distances. Fatigue during long-distance exercise can arise from several factors including:

  • Low energy supply
  • Lactic acid production
  • Electrolyte imbalance and fluid loss
  • Central fatigue

Finishing a 100 km endurance ride requires the horse to have adequate energy supply before and during the race. Horses also need to maintain fluid and electrolyte balance.

Factors Affecting Performance

It takes a lot to prepare your horse to compete successfully in endurance competitions.

In the following section, we explore some of the factors that affect the performance of endurance horses.

Energy Levels

Horses store energy in the form of glycogen in muscle and liver and as fat in adipose tissue. To a lesser extent, amino acids (from protein breakdown) can also be used for energy.

Glycogen is a branched structure of glucose (sugar) molecules bound together. During exercise, glycogen and fat are broken down to make energy in the form of ATP (adenosine triphosphate). This powers muscle contraction and other processes involved in exercise.

Glycogen provides a rapidly available source of energy. However, glycogen stores can be depleted by 50 – 75% in a low-speed endurance ride. This means the horse will need to rely on stored fat, amino acids, and dietary sugar to extract energy.

Fatigue arises when blood glucose levels are low and amino acid breakdown is accelerated.

Body Weight and Condition

The body weight and condition of your horse significantly impact performance and ability to finish the race. An ideal body condition score for endurance horses is 4 – 4.5 on the 9-point Henneke scale.

Thin, under-conditioned horses have lower energy reserves to support them through the ride and may fatigue early. Horses with a low body condition are more likely to be eliminated from a race early due to metabolic problems.

In a study of horses in the Tevis Cup, all horses starting the race with a body condition score of less than 3 failed to complete the course. [32]

Over-conditioned horses carry excess weight, which puts them at a disadvantage because they require more energy to move at a consistent speed. Excess fat also has an insulating effect which makes it more difficult to dissipate heat.

In one study, the total body fat composition of horses that finished a 150-mile ride was 6.5% whereas non-finishers averaged 11% total fat. [31]

Hydration

Bodyweight also includes gut fill and water reserves, which are significant considerations for performance in endurance events.

During a 160-kilometre race, endurance horses can lose 3-7% of their weight, mostly from loss of fluids. [33]

The large intestine serves as a major water reservoir, helping to offset the loss of fluids and electrolytes in sweat. The intestinal water reservoir can represent 8 to 10% of the horse’s body weight, holding up to 50 L of water. [33]

While horses need to be adequately hydrated to compete at a high level, giving your horse too much water can actually decrease performance by increasing the weight a horse has to carry.

Fatigue

Fatigue arises from central (neurological) or peripheral (physiological) causes. Amino acid catabolism and low glucose levels are common reasons for central fatigue. [1]

As exercise progresses in long rides, amino acids are broken down for energy. In particular, when branched-chain amino acids (BCAAs) are used for energy by muscle, the concentrations of BCAAs in the blood first increase and then decrease.

BCAAs compete with the amino acid tryptophan for entry into the brain at the blood-brain barrier. When BCAA levels are low, more tryptophan can enter the brain. This increases serotonin production, which is a neurotransmitter that elicits fatigue. [35]

Peripheral fatigue – such as an inability to sustain muscle contraction – arises from electrolyte and fluid imbalances, low energy supply and lactic acid accumulation.

Health Concerns

As the pace of endurance races has increased, higher rates of health and safety issues have led to elimination from the races.

Horses are evaluated by a veterinarian before, during and after the race to assess whether they are able to compete or continue in the competition. The most common reasons for elimination from a race include:

  • Lameness
  • Dehydration
  • Metabolic disorders

Colic is another common reason for elimination from a race and is the leading cause of death in endurance horses.

Nutritional Needs

The nutritional requirements of horses competing in long-distance races are different from the requirements of show jumpers or sprint-based disciplines, such as barrel racing.

Endurance horses in heavy exercise have 60% higher energy requirements compared to horses at maintenance and 36% higher protein requirements.[2]

Elite endurance horses that maintain higher speeds are classified under very heavy exercise by the NRC. For these horses, the energy requirement is 89% above maintenance and the protein requirement is 60% higher. [3]

However, the estimated intake only increases by 25% for heavily exercised horses. [3] This means that the nutritional density of the diet must be increased to provide more calories and protein while only increasing the dry matter content of the diet by 25%.

Regardless of exercise level, all horses should consume a diet composed of approximately 80% forage (hay or haylage) and they should consume a minimum of 2% of their body weight in forage per day.

One of the greatest challenges when feeding endurance horses is providing enough feed to meet macronutrient requirements without sacrificing forage intake.

It should be noted that several studies show horses can consume up to 3% of their body weight in hay (dry matter). [38] Therefore, depending on the quality of the forage, it may be possible to meet their energy and protein needs from forage alone.

However, even if energy and protein needs are met on a forage-only diet, there are likely to be significant gaps in micronutrients including vitamins and minerals.

7-Step Guide to Feeding Endurance Horses

What should you be feeding your endurance horse to maximize their performance before a race and support their recovery post-race?

Follow these seven steps to feeding and caring for your horse to prepare for long-distance riding.

1) Assess your Horse’s Health

Before beginning race training, consult with your veterinarian and farrier to assess your horse’s health and baseline status.

Endurance horses should be examined for:

  • Heart problems such as arrhythmias
  • Respiratory issues such as inflammatory airway disease
  • Musculoskeletal concerns
  • Foot balance issues

Horses should be in lean condition (4 – 4.5 out of 9 on the body condition score) and should be up to date with their vaccination schedule, dental checks, and deworming program.

You should also consider whether your tack is appropriate for long-distance riding. Endurance riding puts a lot of strain on the horse and ill-fitting tack can lead to musculoskeletal and behavioural issues.

2) Feed High-Quality Forage

High-quality forage should be the primary energy source for all endurance horses and should make up a minimum of 80% of the diet to support gut health.

Choosing a high-quality forage means looking for grass hay with minimal seedheads and soft stems or green, leafy alfalfa with soft stems. A hay analysis is always recommended to know the nutrient profile of your forage and appropriately balance the diet.

Unlike grains, forage has a low glycaemic effect, meaning it does not result in large blood glucose and insulin fluctuations. Instead, forage is digested slowly in the hindgut providing a more sustained source of energy as the horse races. [2]

Forage fermentation in the hindgut produces volatile fatty acids (VFAs), which are absorbed and easily converted into energy in the muscles and liver. [2] VFAs can provide up to 42% of the horse’s energy requirements.

Forage consumption also stimulates thirst to promote water intake and helps to prevent dehydration by increasing retention of water and electrolytes in the gut. [10]

Research shows that sodium levels in the blood are higher post-racing in horses fed a high-forage diet compared to those on a low-forage diet. [11]

Note that this improvement in water and electrolyte balances with a high-forage diet will also increase the weight of the horse which can put them at a disadvantage during the race.

3) Add Calorie Sources

Endurance horses have extremely high energy demands when in training and during races. They require slow-release energy sources as fuel for long competitions.

Although forage should be the primary energy source for your horse, additional calories are usually required.

Fibre Sources

Soluble fibre sources such as beet pulp or soy hulls are good options to feed endurance horses. These concentrates provide energy through fermentation in the hindgut but have less bulk than forages.

In one study, horses fed soluble fibre to replace 50% of grass hay were slightly heavier at the start of the race compared to horses consuming just grass hay. This is likely due to a larger water reservoir in the hindgut, meaning these horses did not need to drink as much water during the race. [36]

Other feeds such as partially extruded linseed (flaxseed) and wheat bran have relatively high water holding capacity as well and are good options for endurance horses. [37]

Grains

Grains can also be provided to add energy to the diet, but their use should be limited.

Oats, barley and wheat are high in starch and have a high glycaemic effect, causing a rapid increase in blood glucose and insulin levels. [7][8]

Grains supply quick calories but are not likely to sustain the horse over a long endurance ride. Feeding large quantities of grain is not recommended as this can lead to digestive health issues such as gastric ulcers and hindgut acidosis.

Small quantities of grain may be provided at vet gates throughout races in the form of a palatable mash to provide rapid-release energy. This can support fat breakdown and ensures glucose is available to cross the blood-brain barrier. [6]

Wheat bran is the most appropriate grain to feed in small quantities to endurance horses. Wheat bran has high digestible energy content and produces a lower glycaemic response in comparison to barley, corn, and oats. [7]

Fats and Oils

Fat is an ideal energy source for endurance horses. All fats provide 9 calories per gram, which is double the calories provided by carbohydrates and proteins.

Fat is metabolized aerobically, meaning that oxygen is required to convert fat into energy. Endurance horses typically exercise at below their VO2 max and can supply enough oxygen to their muscle cells to support aerobic metabolism. [1][4]

Feeding fat also has a number of additional benefits: [6][14][15][16]

  • Fat is a cool energy source with slow, sustained release
  • Fat adds little dietary bulk, enabling endurance horses to expend less energy when racing
  • Fat breakdown does not produce lactate, which induces fatigue
  • Feeding fat limits the breakdown of glycogen stores
  • Fat produces less metabolic heat compared to carbohydrate and protein metabolism

Fat must be introduced gradually and increased over a 6-11 week period. This allows the body to adapt by producing more fat-digesting enzymes. [14]

Fat Sources

For endurance horses, 7-15% of the total diet can consist of fat.

Soy, vegetable, canola, flaxseed (linseed), camelina, and corn oils are suitable fats for horses. [1]. Although all fats will provide the same calorie density, the fatty acid profile will differ.

When feeding large volumes of oil, choose balanced sources with high levels of anti-inflammatory omega-3 fatty acids. You may want to supplement with flax oil, fish oil or w-3 oil to boost the content of beneficial omega-3’s.

It is recommended to increase antioxidant supply in the diet when supplementing with fat to combat increased production of free radicals.

Antioxidants such as vitamin E, vitamin C and selenium allow the horse to efficiently metabolize fat. [18] Increase vitamin E by 100 – 150 IU for every 100 ml of vegetable oil. [5]

4) Optimize Protein Levels

Endurance horses have increased protein requirements due to protein breakdown during exercise and to support muscle repair post-workout. [6]

Endurance horses do not always require additional protein supplementation if they are on a high-quality forage. You can submit a hay sample for analysis to know how much protein your horse is getting from hay.

However, even if your horse’s overall protein intake is adequate, there may be certain amino acids that are deficient. Amino acids are the molecules that make up protein.

In equine diets, lysine, methionine and threonine are the three essential amino acids that are most likely to be deficient.

These are considered limiting amino acids because if they are not supplied in the right amounts, they can limit the rate of protein synthesis in the body, potentially impairing muscle recovery, immune function and performance.

If more protein is required in the diet, look for high lysine options, such as soybean meal or roasted soybeans. Work with a nutritionist to determine an appropriate feeding rate. You may also want to supplement directly with amino acids to address imbalances in the diet.

Note that feeding excess protein can be detrimental for endurance horses. [6] Excess protein is broken down in the body producing ammonia, which needs to be excreted in the urine. This process makes the horse more prone to dehydration.

Avoid high protein complete feeds (above 14%) as these will likely oversupply protein.

Branched Chain Amino Acids

Endurance horses are sometimes fed supplements containing branched-chain amino acids (BCAAs), which include leucine, isoleucine and valine. [1]

These can be broken down to contribute 3-15% of the energy requirement when racing and help prevent central fatigue. [19]

5) Ensure Vitamin and Minerals Requirements are Met

The prolonged exercise of the endurance discipline results in muscle damage and overall fatigue. These horses have increased requirements for antioxidant nutrients (vitamins E & C and selenium) to support muscle function.

B-vitamin supplementation is also important for sport horses because these micronutrients serve as cofactors for many metabolic processes.

Although B-vitamins are made by microbes in the hindgut, endogenous production is not likely to be sufficient to meet the horse’s horse’s needs during intense exercise.

Mad Barn’s Omneity is a comprehensive vitamin and mineral supplement used by many endurance horses. Omneity provides high levels of vitamin E, a full B-vitamin profile, amino acids, and 100% organic trace minerals for better absorption.

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6) Support Electrolyte Balance

An estimated 7.2% of endurance horses retire during races due to electrolyte imbalances. Electrolyte minerals such as sodium, potassium and magnesium are lost in sweat during exercise. [23]

A horse’s sweat is hypertonic, meaning it is more concentrated with electrolytes compared to their blood.

In comparison, humans and many other mammals have hypotonic sweat, which is less concentrated with electrolytes than blood. As humans sweat, they retain a higher concentration of electrolytes within the body.

Because a horse’s sweat is hypertonic, horses are at higher risk of electrolyte imbalance in hot temperatures or when heavily exercising. The amount of sweat and electrolytes lost depends on the ambient temperature, humidity, and the horse’s diet.

Table 1: Sweat Mineral Composition in Horses [34]

Hypertonic Sweat Loss (mmol/litre)
Sodium 132 – 249
Potassium 28 – 53
Chloride 140 – 301
Calcium 2-9
Magnesium 1-3

Metabolic Alkalosis

In extreme cases, loss of electrolytes through sweat can result in alkaline blood pH and a condition known as metabolic alkalosis. This is extremely detrimental to the horse. [22][24]

Specifically, the loss of chloride ions in sweat cause the kidneys to retain bicarbonate, which increases blood pH. If metabolic alkalosis occurs, this can lead to fatigue and cardiac arrhythmias. [25][26][27]

The signs of alkalosis include: [25]

  • Dehydration
  • Sweating
  • Ataxia (altered gait)
  • Low mood
  • Abdominal pain
  • Lameness
  • Recumbency and lethargy
  • Clinical myopathy (painful, hard muscles)
  • Temperature exceeding 42 degrees Celsius
  • Tachycardia (high heart rate) and tachypnoea (high breathing rate)

Electrolyte Supplementation

Electrolyte supplements are typically provided in powder form and contain varying levels of minerals as well as other vitamins and nutrients to support exercise and hydration status.

Mad Barn’s Performance XL is an electrolyte powder that contains sodium, chloride, potassium, calcium and magnesium in a balanced ratio to replace minerals lost in sweat.

Performance XL also contains vitamins E and C, as well as dextrose and sucrose (sugar) to help horses to recover after strenuous exercise. The formulation for this supplement is based on research in high end performance horses conducted at the University of Guelph.

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How to Feed Electrolytes

These powders can be top-dressed on feed, but it is recommended to dissolve electrolytes in water or a mash feed to encourage water intake. [28] Electrolytes stimulate thirst so always provide your horse with free access to fresh water when feeding these supplements.

Providing access to water also reduces the risk of digestive complications. Research shows that horses given electrolytes without ad libitum water during an endurance ride had higher rates of colic (21%) compared to those given electrolytes with ad libitum water (0%). [28]

Electrolytes can also be administered as a paste, but this format is not recommended. Pastes re very concentrated and draw water into the stomach, potentially contributing to dehydration. Paste-based electrolytes also can contribute to gastric ulcers.

When to Feed Electrolytes

Electrolytes can be provided before, during and after a race to prevent issues such as alkalosis.

Before the race

Endurance horses are often electrolyte-loaded in the days leading up to a race to prevent alkalosis. However, this may not be beneficial.

It is recommended to give electrolytes two hours pre-race. [24]

During the race

Endurance horses are fed small palatable meals during the race to provide calories and support mineral balance. These meals typically include some grains, fibre, fat, and electrolytes.

Electrolytes can also be supplemented in water during a race. [26]

After the race

Mineral imbalances are greatest 30-minutes post-racing and the risk of alkalosis persists 12-24 hours post-competing. It is essential to supplement electrolytes after completion of the race to replenish levels of minerals lost in sweat and urine. [24]

7) Support Hydration

In addition to providing your horse with adequate electrolyte supplementation, it is also important to ensure they are getting enough water. Dehydration is not only a health concern, but is also correlated with poor race performance. [26][28]

Racing endurance horses lose 1 to 15 litres of water per hour through sweat and heat evaporation. By the end of a race, a horse may have a deficit of 40 litres of water (4 – 7% bodyweight).

During races, vet gates should offer a choice of fresh water and electrolyte- or sugar-supplemented water. Research shows that horses offered only electrolyte-enriched water drink less than horses offered a variety of water types.

To increase water consumption and palatability, consider adding flavouring with apple juice or molasses. Water that is added to feeds to make a mash can also help support hydration.

Another strategy is to feed soaked hay pre- and post-racing. Soaked hay should be fed with caution as it is heavy, reducing the horse’s power-to-weight ratio, and can cause bowel issues. [30]

You should also monitor your horse’s water intake to ensure they are not drinking too much water. Unlimited water access while racing can result in osmotic shock related to changes in blood volume.

Example Feeding Program for Endurance Horses

The table below highlights the difference in nutrient requirements for a typical horse at maintenance compared to an endurance horse in hard work.

Table 2: NRC dietary requirements at maintenance vs. heavy exercise for a 500 kg (1100 lb) horse [3]

Workload Intake
(% bodyweight)
Protein Requirement
(grams/day)
Energy Requirement
(mcal/day)
Maintenance 2 630 16.6
Heavy exercise 2.5 861 26.6

 
These increased needs can be met by providing high-quality forage, additional fibre sources, and oil supplements.

The following sample feeding plan uses a mixed hay with 10% protein content, fed alongside beet pulp and w-3 oil. Added salt and electrolytes are provided as well as a vitamin and mineral supplement to meet all NRC nutrient requirements.

Table 3: Example diet for an endurance horse weighing 500 kg (1100 lb) in heavy exercise

Feed Endurance Horse Diet
(Amount / Day)
Mixed hay (10% crude protein) 13 kg (28.5 lb)
Beet pulp 1 kg (2.2 lb) (dry weight)
w-3 Oil 210 ml (7 oz)
Performance XL: Electrolytes 60 g (2 scoops)
Salt 30 g (2 tbsps)
Omneity Premix 120 g (4 scoops)
Diet Analysis
Digestible Energy (% of Req) 101%
Protein (% of Req) 142%
NSC (% Diet) 9.1%
Fat (% Diet) 4.3%

 

Summary

Endurance horses perform best when fed a forage-based diet with high energy and nutrient density. Their body condition should be closely monitored to ensure they are not carrying too little or too much body fat.

These horses may be fed small grain-based meals during a race, but should avoid excess grain consumption. Grains have a high glycemic response and quickly spike blood sugar.

Instead, fat is preferred as an energy source because it has a low glycaemic response and provides slow-release energy. You can gradually increase fat in your horse’s diet to 7-12% total intake over 6-11 weeks.

Care must be taken to balance the endurance horse’s diet and supply adequate vitamins, minerals and protein to promote racing success.

However, too much protein can negatively impact performance. Protein levels in balancers and feeds should not exceed 10-12%. Avoid feeding alfalfa hay on its own as this legume forage has high protein content.

Preventing dehydration and alkalosis are key challenges in the racing endurance horse. Horses can lose up to 7% bodyweight during long-distances races – primarily due to dehydration.

Supplement with electrolytes dissolved in a mash or water and always give your horse access to fresh, clean water.

For help with formulating a diet for your endurance horse, submit your horse’s information online and our nutritionists will provide a free diet balancing.

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References

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