Electrolyte Balance – vital to the proper functioning of a racehorse's system

Words - Dr. Cath Dunnett

Electrolytes are essential components of the racehorse’s diet as they are vital to the proper functioning of the body’s basic physiological processes, such as nerve conduction, muscle contraction, fluid balance and skeletal integrity. The major electrolytes, sodium, potassium, chloride, calcium and magnesium are widely distributed within the body, but can be more concentrated in particular organs and tissues. For example, the level of potassium is very high in red blood cells but quite low in plasma, and the level of calcium in blood is low, but comparatively very high in bone and in muscle cells. The body has in-built mechanisms that work to maintain the correct electrolyte balance within the tissues, fluids and cells. These modify the absorption of electrolytes in the gut, or their excretion by the kidneys. These mechanisms are not foolproof however, and electrolyte loss through sweat can be a major issue for Thoroughbreds. The sweat of the equine athlete, unlike its human counterpart, is hypertonic; meaning that horse sweat contains higher levels of electrolytes than the circulating blood plasma. Consequently, the horse loses comparatively large quantities of electrolytes through sweating.

Although the electrolyte composition of equine sweat varies between individuals, on average a litre would contain about 3.5g of sodium, 6g of chloride, 1.2g of potassium and 0.1g of calcium. From this we can see that the majority of the electrolyte lost is in the form of sodium and chloride or ‘salt’. The amount of sweat produced on a daily basis and therefore the quantity of electrolytes lost differs from horse to horse and depends on a number of factors. As sweating is primarily a cooling mechanism, how hard a horse is working, i.e. the duration and intensity of exercise and both the temperature and humidity of the environment are all significant. Horses can easily produce 10 litres of sweat per hour when working hard in hot humid conditions. Stressful situations can also cause greatly increased sweating.

For example, during transport horses can lose a significant amount of electrolyte through sweating and the opportunity for replenishing this loss through the diet may be less as feeding frequency is reduced. Use of electrolyte supplements either in the form of powders or pastes is advocated before, during and after travel, especially over long distances. A number of air freight transport companies advise trainers to use a powdered electrolyte supplement added to the feed on a regular basis given for the 3 days prior to travel. As this helps offset much of the loss normally incurred during transport and subsequently the horses arrive at their destination in better shape. Electrolyte supplementation is a valuable attribute in the ongoing battle to reduce in-flight dehydration.

Electrolytes lost from the body in sweat must be replenished through the diet. All feeds, including forages, have a natural electrolyte content and in concentrate feeds this is usually enhanced by the addition of ‘salt’, which is sodium chloride. Forages such as grass, hay, haylage or alfalfa (lucerne) naturally contain a large amount of potassium, as can be seen from the table 1 below. In fact, 5kg of hay for example, would provide in the region of 75g of potassium, which largely meets the potassium needs of a horse in training. It is therefore questionable whether an electrolyte supplement needs to routinely contain very much potassium unless forage intake is low. Calcium is another important electrolyte, but it is lost in sweat in only very small amounts and its availability in the diet tends to be very good.

Calcium is particularly abundant in alfalfa with each kilogram of the forage providing nearly 1.5g of calcium. A kilo of alfalfa alone would therefore go a long way towards replacing the likely calcium loss through sweating. In addition, the calcium found in alfalfa is very ‘available’ to the horse in comparison to other sources, such as limestone. Calcium gluconate is another very available source of calcium, however, it has a relatively low calcium content compared to limestone (9% vs. 38%) and so much more needs to be fed to achieve an equivalent calcium intake. Interestingly, there is great variation between individual horses in their ability to absorb calcium, however, scientific studies carried out at Edinburgh Vet School showed that this variability was considerably less when a natural calcium source in the form of alfalfa was fed.

By far the most important electrolytes to add to the feed are sodium and chloride or ‘salt’. The levels of sodium and chloride found in forage are quite low and due to manufacturing constraints only limited amounts of salt can be added to traditional racing feeds. A typical Racehorse Cube fed at a daily intake of 5kg (11lbs) would provide only about 20g of sodium and 30g of chloride. As can be seen from table 2 this is a fair way short of meeting the daily requirements for these particular electrolytes by a racehorse in hard work.

It is therefore very important that supplemental sodium and chloride is fed. Ordinary table salt is by far the simplest and most economical electrolyte supplement, but the downside is the issue of palatability as the addition of larger quantities of salt to the daily feed can cause problems with horses ‘eating up’. As an alternative salt could be added to the water, but only when a choice of water with and without salt is offered. Salt should not be added to the water if it puts a horse off from drinking, as dehydration will become a problem.

Inadequate water intake can also contribute to impaction colic. Saltlicks are another alternative, although intake can be very variable and we rely on the horse’s innate ability to realise its own salt requirements, which is questionable. So addition to the feed is by far the best route for adding salt or electrolyte supplements to the diet. Splitting the daily intake between two or three feeds can reduce problems with palatability.

Mixing salt and Lo Salt can make another simple DIY electrolyte supplement in the proportion of for example 500g to 250g respectively. Salt is sodium chloride (NaCl), whilst Lo Salt contains a mixture of sodium chloride and potassium chloride (KCl). This formulation provides 3g of sodium, 6g of chloride and 1g of potassium per 10g measure. This DIY mixture will replace these electrolytes in the approximate proportions that they are lost in sweat. What are the implications of a racehorse’s diet containing too little or too much of an electrolyte and how can we assess this? An inadequate level of certain electrolytes in the diet in some horses may simply result in reduced performance. In other individuals, it can make them more susceptible to conditions such as rhabdomyolysis (tying up), or synchronous diaphragmatic flutter (thumps), both of which are regularly seen in horses in training. Conversely, an excess electrolyte intake is efficiently dealt with by the kidneys and is ultimately removed from the body via the urine.

Therefore, the most obvious effect of an excessive electrolyte intake is increased drinking and urination. For this reason, the use of water buckets rather than automatic drinkers is preferred, as whilst the latter are far more labour efficient, the ability to assess water intake daily is lost. Excessive electrolyte intake can also be a causative factor in diarrhoea and some forms of colic. There is also some recent evidence in the scientific press that suggests that repeated electrolyte supplementation might aggravate gastric ulcers. However, these early studies used an electrolyte administration protocol typical of that seen during endurance racing, rather than simply a daily or twice daily administration, which is more commonly used in racing.

Supplements that contain forms of electrolyte that dissolve more slowly in the stomach, however, may be less aggressive to the sensitive mucosa. Unfortunately blood levels of sodium, potassium, chloride or calcium are poor indicators of whether dietary intake is sufficient or excessive unless it is very severe. This is because the body has effective systems for regulating the levels of these electrolytes in blood within very tight physiological limits. A creatinine clearance test, which measures the electrolyte content of a paired blood and urine sample is a much more useful indicator of dietary electrolyte adequacy.

There are a large number of commercial electrolyte products available, with a wide range in the breadth of ingredients that they contain. Consequently, they vary enormously in the amount of electrolyte that they deliver per recommended daily dose, as can be seen in table 3. In addition, whilst some glucose or other carbohydrate can help improve palatability, its presence should not compromise the amount of electrolyte that is contained within the supplement. In humans, it is recognised that the uptake of sodium from the gut is improved in the presence of glucose, while this effect in horses has not been firmly established. Electrolyte paste products are also often used either before and or after racing or travel.

These products are useful as they allow rapid electrolyte intake even when feed eaten may be reduced following racing. These electrolyte pastes often provide a more concentrated form of supplement and it is extremely important to ensure that the horse has access to water immediately following their use. Failure to do this may mean that the concentration of electrolytes in the gut actually draws water from the circulating blood, which can exacerbate dehydration. Another disadvantage with paste supplements is that if they are not formulated well, with an appropriate consistency, they can be difficult to dispense from a syringe and the horse may also be able to spit most of the product out after administration.

Some simple rules of thumb for choosing a good electrolyte are that salt should be one of the first ingredients listed on pack, as all ingredients are listed in descending order of inclusion. Additionally, be wary of supplements that taste sweet, as they may contain a lot of carbohydrate filler and little electrolyte. Some electrolyte supplements also contain many superfluous ingredients such as vitamins and trace minerals. The inclusion of these latter ingredients is largely unwarranted and their presence could cause issues with oversupply if the electrolyte is multi-dosed daily. Some electrolyte products specifically marketed towards racing may also contain bicarbonate.

The theory behind its inclusion is sound as ‘milk shaking’, whilst outside the rules of racing, has some scientific validity. However, the limited amount of bicarbonate contained in such electrolyte supplements is unlikely to have the positive effect on performance attributed to the former practice. Other extra ingredients such as pre-biotics may be more useful as they may improve the absorption of some electrolytes. In Summary, electrolyte supplementation in one form or another is essential within a racing diet. Ensuring that you are using a good electrolyte supplement is important and the quantities fed must be flexible and respond to changes in the level of work, degree of sweating and climate.

Clean Water and horses - the importance of this often forgotten essential nutrient

Words - Alan Creighton

The Irish Equine Centre monitors the environment in over 200 racing yards across Europe. That monitoring package includes air quality, feed and fodder quality and storage, stable hygiene testing, and indoor exercise hygiene testing. A further major portion of that environmental monitoring package includes regular water sampling both at source and water directly from buckets or troughs. Water is the number-one nutrient fed to any animal, and it is often overlooked both in nutrient programmes and in the diagnosis of health issues resulting from poor performance of racehorses. We often hear the excuse that “Ah sure, horses drink from dirty puddles and ponds; and they seem fine.” That may be true and even OK for horses on farms, where horses are on a break or at pasture, but it’s OK not for high- level stressed racehorses. Anything that affects the gut flora or metabolism of a racehorse can have a negative effect on performance.

By weight, horses consume up to three times as much water as food per day. If the water contains toxins, high levels of minerals or any other environmental contamination, nutritional and performance problems can result.

Horses should consume enough water to replace what is lost through faeces, urine and importantly for racehorses, sweat particularly due to exercise. Water consumption will depend on several factors. These factors can be variable and include temperature, humidity, feed and fodder quality, type and amount of feed and fodder, exercise level, stage of fitness and health. The average daily consumption for a 500kg horse would be approximately 45 litres per day in normal, average weather conditions. The same horse, when in full training, could consume nearly three times that or up to 125 litres of water per day. When racehorses are carrying out their conditioning or fitness work following a long break, particularly in warm weather, the sweat production can increase further, which in turn increases the water and electrolyte requirements.

At this stage of conditioning, there is a fine balance between water and electrolyte concentration, which is essential for appropriate muscle contraction and also in the cooling down process of the horse. An imbalance or a depletion of electrolytes can lead to premature muscle fatigue, reduced stamina, muscle cramps, poor post exercise recovery and tying up. These facts further highlight the need to ensure an abundant, safe supply of water to racehorses. 

Contaminated water will impact the performance of both. This is something that may be overlooked in all types of horse management. High bacterial content in water can affect all animals, and in particular young stock and under-pressure racehorses. High iron content in water can cause severe gut upset in horses, which builds up over time. High levels of nitrate, nitrite and aluminium can also have a large negative impact on horses. Water quality in farm wells can fluctuate greatly and require constant monitoring.

There are three main sources of water available to racehorses: mains or municipal water, well or borehole water and finally running water in streams, if using outdoor paddocks daily. Yards in or close to towns usually draw their water from a public or municipal system that provides extensive purification and filtration services and also regularly tests its water for contaminants such as disease-causing bacteria and toxic chemicals including pesticides. The worries are less from this source but not eliminated. If there is damage to the delivery line or a problem with the plumbing on your own yard or farm, your water could still be compromised. Mains water can also be variable in the concentration of fluoride and chlorine, which means it requires regular monitoring as this may affect the palatability of water.

If your drinking water comes from a small group scheme or your own private well, then you are responsible for ensuring it is safe to drink. Many wells provide beautifully clean water, but there is also the potential for contamination. Man-made water sources are not free of issues; they require consistent maintenance.

Wells which are drilled correctly, sealed and more than 50 feet (15m) deep have less chance of becoming contaminated with bacteria. Water from an old or shallow well should be tested more frequently. Wells close together can supply water of varying quality. Even two wells side by side can draw water from separate aquifers (underground water sources) and yield very different results. Water quality from wells, both in terms of bacterial content and physical and mineral makeup, can vary greatly based on seasonal factors. Drought, heavy rainfall, local farming practices all can have a negative impact.

Trainers more and more are seeing the benefits of keeping racehorses in outdoor paddocks either for a portion of the day or permanently. If the water source is only a stream or river, then obviously a good flow is required. Ponds are usually problematic. Agricultural chemicals and other environmental contaminants can cause blue-green algae to bloom in the water. Not all algae produce harmful chemicals, but blooms are indicators of unhealthy or stagnant water.

Horse owners often forget to observe or clean water troughs in paddocks. If the water in a trough appears green or murky, it needs to be dumped and replaced. When cleaning a water trough, it is often necessary to remove algae by more vigorous means than rinsing alone. Stiff brushes and apple cider vinegar are two safe tools for removing algae and discouraging regrowth. 

Like us, however, their water intake can quickly be adversely affected if the water’s taste is unpleasant. Horses that refuse to drink from unfamiliar-tasting water sources are distressingly common. There is more and more evidence to suggest that horses are reluctant to drink low pH or acidic water. You may have a scenario where a horse is used to drinking a balanced pH water (6.5-7.5) and then travels to a racetrack were the pH may be much lower (4.5-5.5) and then refuse to drink, which would be a problem and lead to dehydration if stabled there for a number of days.

The most common problem we find in water is bacterial contamination. Testing your well’s water for bacterial contamination on a regular basis is sound practice. A total coliform test checks the water for bacteria normally found in the soil, surface water, and human and animal waste. Coliform bacteria are not, in themselves, considered harmful, but their presence in your water supply is an indication that your well or supply may be contaminated either from runoff from a manure pit, a nearby septic tank, or fertiliser or manure spread on a nearby farm. Coliform levels can vary greatly due to drought conditions or with sudden heavy rainfall. It’s also possible to have high coliform levels when the well has developed physical defects, such as a broken or missing cap that could allow debris, surface water, insects or rodents inside. Bacterial testing is a good idea whenever there is a noticeable change in the colour, odour or taste of your water, or if a group of animals become sick. 

If high coliform levels turn up in your well water, it’s possible your own manure management is the culprit. To protect your water, make sure you situate your manure pit in an elevated, well-drained location, not on the lowest spot on the property. After a rainstorm, watch the flow of water—it should go around your manure pile, not through it. Simply rerouting the flow of run-off water can improve your water quality considerably. 

The variability of bacterial levels in water supplies often results in trainers needing to install a UV filter onto the water inlet pipe, which feeds their yard. UV filters, once working correctly and maintained, are effective at reducing the bacterial load.

Blue-green algae in natural water sources can produce cyanotoxins, which are extremely dangerous for horses. Blue-green algae poisoning can cause muscle tremors, laboured breathing, bloody diarrhoea, liver damage and even convulsions and death. So it’s best to remove horses from a contaminated water source with algal blooms immediately. Algal growth is usually associated with large amounts of organic material in the water, often as a result of runoff from nearby fertilised fields.

Nitrate levels in natural or well water supplies are also a concern. Nitrate converts to the much more toxic nitrite in the rumen, which reacts with blood haemoglobin, reducing the availability of the blood to hold oxygen. Nitrites and ammonia should only be present in drinking water at very low levels. Ammonia may be present in supplies as a result of runoff from agricultural slurry, fertiliser or industrial waste. It rapidly oxidises to nitrite (which principally exists as an intermediate) and, in turn, to nitrate. Elevated levels of ammonia and nitrites are indicative of effluent contamination, and the source should be investigated and eliminated. For drinking purposes, removing nitrate is required and can be carried out by the installation of a reverse osmosis (RO) system.

When it comes to water safety, pesticides and herbicides are other worries. Though it can be expensive to test for these chemicals, it may be worth doing if you have significant concerns about the agricultural sprays being used in your area, or if you suspect solvents or other toxic chemicals have leached into your water from a nearby industrial facility. 

Until recently, the veterinary world had viewed iron toxicity in horses mainly as an acute condition and often only as a result of overdosing on iron supplements. However, research has shown that horses exposed to high iron levels in water, grass or hay over a prolonged period can accumulate the mineral in their livers, resulting in chronic iron overload. This iron overload can prevent the liver from carrying out its essential duties so vital to an exercising racehorse. High iron in water also can have a detrimental effect on the gut flora of horses, which can lead to all types of metabolic issues. Iron levels in well water vary greatly from region to region, and many hotspots have been identified over vast areas in different countries. Iron, like most minerals, can be filtered from water using filtration systems at the point of entry into the yard.

Once trainers have established a reliable clean source of water, they must then ensure that the distribution of clean water is maintained throughout the yard. That means placing covers on header tanks to prevent rodent or bird infiltration, cleaning water bowls, drinkers and buckets and finally flushing water lines to automatic drinkers on an annual basis. 

Then there’s the  question of which is better: watering using buckets or automatic drinkers? Both have positives and negatives. You can monitor the amount a horse drinks from buckets and then take buckets out of the box to clean as needed. The down side to bucketed water is that it’s labour intensive. Automatic drinkers are not labour intensive, but they do need to be checked daily to ensure they are working. They supply fresh water constantly, but you have no idea how much water a horse has drunk or not, and the systems need constant flushing and cleaning. 

Not all natural water sources are problematic, and not all artificially provided water is safe. Keeping a careful watch over the water your horses are drinking will allow you to detect contamination issues before they cause illness, dehydration or loss of performance.

Drinking water must be completely free from any microorganisms or contaminants which are considered a health risk.

The IEC provides water testing for equine, agricultural, domestic and commercial purposes. Water is tested for bacterial content including E. coli and total coliforms but also physical and equine-specific mineral profiles to an ISO 17025 standard. Water can pose a health risk for humans and animals when consumed, even though contamination may not be noticeable by taste, smell or even colour.