As equestrian pursuits are experiencing a huge rise in popularity across the UK, it seems only prudent to detail the essential drinking water requirements of Horses. Please note: If any of the following text causes concern or raises questions pertinent to your own Horse, then please do not hesitate to contact your local Vet specialising in Horses for her/his advice.

Horses are not exactly the same in their drinking water needs as other hoofed animals. Most (but sadly not all) keepers of this most majestic of beasts, know by experience what their particular charge requires on a daily basis. However, those that are new to the keeping of Horses, or those that sadly assume ‘that any water’ is suitable should understand that the ‘wrong’ quality of drinking water can not only make the animal refuse to drink, but can seriously damage the animals health by either direct damage caused by toxic compounds or by starting a chain reaction in the Horses gut that through the generation of toxins, can lead to a particular animals death. Please remember the ancient folk saying that has been passed down (by various cultures) through the centuries: ‘You can lead a Horse to water but you can’t make it drink’’. It has always been understood by Horse using cultures across the globe that the animal itself has the ability to sense or taste for some of the easier to identify toxins.

Water for Horses

It should be obvious that an adequate supply of good-quality, clean drinking water is essential for Horses. Under proper care, the Horse should have free access to fresh, pure water at all times; devoid of any chemical compounds or biological organisms that may cause illness or distress, of a quality similar to human needs. However, the exact drinking water requirements for the Horse have been hard to define in the past because numerous dietary and environmental factors affect water absorption and excretion in this most difficult of ungulates. Unlike most other herbivores, the digestive system of the Horse is considered monogastric (single stomach) rather than ruminant. The digestive tract includes the stomach, small intestine and large intestine. The stomach and small intestine are commonly referred to as the upper gut, where most of the protein, fat, vitamins and minerals contained in feed are digested and absorbed. Although the Horse lacks the complex fore-stomach of a ruminant, unique characteristics of its large intestine, or hindgut, allow the horse to utilise cellulose and other fermentable substrates in much the same way as ruminants. In the Horse, water is absorbed from most sections of this digestive tract.

After a meal, water is needed in the gut to dilute the digester – food after it enters the animal – and to maintain the uniform consistency of this digester throughout the gut during the digestive process. If water is consumed without any food being eaten, then the water is absorbed more rapidly and completely. Please note; other dietary factors that may affect absorption include complex polysaccharides (these compounds tend to form gels in the gut and reduce water absorption).

The seemingly totally natural act of drinking for the Horse is a highly complex physiological process that is obviously induced as a result of the dehydration of the Horses body tissues. Most Horses drink during or soon after eating and the frequency of drinking and the water consumed usually increase during hot weather, or after strenuous exercise. When a Horse is thirsty its salivary flow is usually reduced, and the dryness of the mouth may also stimulate drinking.

Physiological variables such as age, growth rate, or lactation are major factors influencing the water requirements for Horses. Adult Horses conserve body water more efficiently than foals, so foals dehydrate more quickly than adults. Adult Horses (just being maintained) require a minimum of 2 litres of water per kg of dry food, whereas foals and young growing Horses may require 3 litres per kg of dry food. An adult Horse needs about 5 litres of water per 100 kg of bodyweight for maintenance. Therefore, foals have a greater requirement for water than an adult Horse in proportion to their size

Also, the Horse’s water requirements may vary substantially depending on ambient temperature, humidity and water loss – e.g. sweating; quantity of urine produced (some mineral compounds in water can act as diuretics) and water content of their food. As in other animals, water requirements will increase as the temperature of their environment increases. For instance, a rise from 15°C to 20°C in temperature will increase water loss by 20 percent and will increase an adult Horse’s water requirements by about 5 litres. The composition of their food has also a major impact on water intake. The amount of water provided by green forage can be very substantial. In fact, the resting Horse grazing grass with moisture content over 70 percent may not need to drink any water at all. Obviously on the other hand, diets that are very dry or high in salt will increase the Horse’s thirst.

Water Deficiency

Inadequate water intake is obviously detrimental to a Horse’s health, and the deficiency of easily obtained clean water may result in the self evident condition called death. The signs of inadequate water intake include the decreased consumption of dry feed, followed by decreased physical activity. It should also be noted that inadequate water intake may increase the risk of intestinal impactions and colic.

Water deprivation for 24, 48, and 72 hours can decrease the normal resting Horse’s body weight by 4, 6.8, and 9 percent, respectively, when the ambient temperature is 63 – 81 °F (17 – 27 °C). Signs of dehydration, such as a dry mouth and sunken eyes are evident when 6 percent or more loss of body weight has occurred. Also, the quality of the drinking water may have a tremendous impact on whether the Horse ‘wants’ to drink, and therefore the Horses water intake may be decreased substantially when the quality of the drinking water is seemingly poor to the particular Horses ‘taste’.

Quality of Drinking Water

An indication of water quality that is most commonly quoted for Horses is the amount of Total Dissolved Solids (TDS) in the water. A TDS of approximately 6,000 ppm constituting common mineral contaminants is generally considered the safe limit in water for Horses. However, if the bulk of the TDS reading is comprised mainly of compounds that may cause adverse or even toxic effects (like Lead or Arsenic for example) then a TDS parameter on its own must be interpreted with caution. Therefore, the water should have a complete chemical analysis to determine the concentrations of specific ions, to identify the toxic compounds that have unsafe levels.

Horses can tolerate Fluoride contamination two to three times greater than cattle. According to Lewis (1995), drinking water containing Fluoride at a concentration of 4 ppm is considered to be marginally safe for Horses, but water containing more than 8 ppm should be avoided at all costs. Please Note: Fluoride is not always added only by water companies across the UK; it can naturally occur in certain geologies and their associated groundwater strata. Chronic Selenium toxicity has been reported as a result of a consumption of water containing 0.0005 to 0.002 ppm of Selenium, but short term intake of water with Se concentrations below 0.01 ppm are not generally considered harmful. Horses may also develop some degree of adaptation to some other water contaminants. For instance, drinking water containing Sulphate concentrations exceeding 1000 ppm may initially cause diarrhoea, but Horses that have adapted to moderate levels of Sulphate can tolerate two to three times this concentration.

Nitrate toxicity is becoming more common in Horses

It is generally assumed that minerals such as Sodium, Potassium, Calcium, Magnesium, Iron, Chloride, and Sulphate at levels commonly found in natural and public water supplies are not toxic to Horses under most practical circumstances. However, at moderately high concentrations, these contaminants may affect the water quality and therefore create a refusal to drink, and of course this may lead to a decreased water intake and therefore dehydration. On the other hand, many potentially toxic compounds that may be present in water do not damage the’ taste’ of water and therefore the Horses water intake, so they are potentially more harmful than those that affect the Horses ‘taste’ or liking for their particular drinking water supply. Nitrate for example is odourless, and tasteless, even at extremely high concentrations. A number of other chemical compounds that may be present in water can also pose a toxicological hazard. Toxic water contaminants that should be totally avoided (or on a practicable basis at least filtered out) include most pesticides, herbicides, heavy metals, Nitrates, Nitrites, Chlorines and Chloramines and most industrial pollutants, and to be on the safe side; most micro-organisms.

Arsenic should also get a mention here – a nasty heavy metal and particularly toxic to most organisms, works by replacing the Life essential Phosphate with Arsenate in the cell (the two compounds are almost identical). Ipso facto, the cell dies. Arsenic is far more prevalent in groundwater supplies across the UK, than most people imagine – Areas of the UK like the Somerset Levels for example, have high levels of Arsenic not too far beneath the surface. So any bore hole has a potential of extracting water with Arsenic in solution. Most of the 400 or so bore holes are known by the local Council, who instruct the landowner how to filter the Arsenic out of solution if the landowner wishes to use the groundwater for most applications. The guidelines for private water extraction (and its intended use) are covered in ‘The Private Water Supply Regulations 2009’. Unfortunately, Arsenic in moderate levels has no ‘taste’ to Horses.

Although Horses may appear to be more tolerant to some water contaminants, it has to be stressed that the quality of certain water supplies may not cause much of a health problem, but rather cause an issue of the Horse refusing to drink. Some Horses may be particularly choosy and outright reject contaminated water especially if the drinking water contains high levels of Chlorine (which has a unique ‘disinfectant’ like smell) or Chloramines, or an unsuitable TDS or pH level. Obviously, in order to be unreservedly accepted by Horses, their drinking water must also be free from any pollution by sewage, farm chemicals, or industrial contaminants of any kind – as well as being potentially toxic, anecdotal evidence suggests that most of these have a ‘taste’ that most Horses dislike.

Nitrate Toxicity

Nitrate toxicity has been rare in Horses but unfortunately is now becoming more common in the UK. In the past, It was most often associated with high Nitrate levels in forage. However, nowadays the Horses drinking water may contribute significantly to the overall burden of dietary Nitrates, especially if it is tap water containing high Nitrate levels, or water from Nitrate contaminated groundwater. Water containing high Nitrate levels resulting from surface contamination from manure, barnyard, and farmland runoff is usually also extremely high in micro organisms. For these reasons alone, Nitrate should be absent from the drinking water of Horses whenever possible.

Nitrates are extremely water soluble and move easily with percolating or runoff water from arable farmland. Therefore, ponds with runoff from heavily fertilised fields and water from poorly lined, shallow wells may contain high levels of Nitrates. Water from deep wells (and bore holes) is usually – but not always – Nitrate free.

However, with Nitrate becoming an ever increasing problem in tap water (as well as groundwater) with Nitrate levels (at certain times) far exceeding the levels set by the UK’s Regulatory Standard for Nitrates in public tap water supplies. It is strongly advised that the keeper/owner of such a magnificent (and expensive) animal have their Horses water supply tested for Nitrates on a regular basis. If any Nitrate levels are found, it is also strongly recommended that adequate Nitrate removal from ANY water supply should be considered wherever possible.

Nitrogen in the form of Nitrate is not especially toxic, but when reduced in the rumen to Nitrite and absorbed into the blood, the Nitrite reduces the oxygen carrying capacity of the blood by reacting with haemoglobin to form methemoglobin, which cannot carry oxygen. Most ruminants have an ability to convert some Nitrate to usable products. In the Horse however, the rumen microbes can readily reduce Nitrate to the more toxic Nitrite form. Therefore, the total amount of Nitrates in the Horses diet is vitally important and subject to abrupt change with the variable growing conditions of harvested and pastured forage and of course, silage.

For example, during a drought, normal silage may accumulate high concentrations of Nitrate and when added to the Nitrate that may be present in the Horses drinking water may result in a lethal combination. Although, the ensiling process should reduce the Nitrate level to acceptable levels after a period of aging for 60 to 90 days in the silo. Unfortunately, unlike other simple-stomached animals such as pigs and sheep, Horses have a cecum that contains colonies of bacteria capable of converting Nitrate to the more toxic Nitrite form. In the past, the preformed Nitrate with its potential Nitrite compounds was rarely encountered in sufficient concentrations in water and feed to be a toxic threat. Unfortunately, high Nitrate concentrations in tap water and dry feed are encountered now on a daily basis. On the other hand, there is also some anecdotal evidence that suggests that Horses who have the correct feed and drinking water that is extremely low in, or totally without Nitrate contamination, have a higher feed to energy ratio than Horses whose feed and drinking water contains this contaminant. This may be because of the slightly higher oxygen levels in a Horses blood supply that consume water and food free of any Nitrate contamination; however, more research needs to be done on this topic.

Bacterial Contamination

In some situations, bacteria in a Horse’s drinking water pose a slightly greater threat than the other possible contaminants in water, because most infectious pathogens enjoy being in solution and therefore, can easily be transmitted via contaminated water. The healthy quality of water can be expressed by counting numbers of coliform bacteria. Not all coliform bacteria are harmful, but their mere presence is a very sensitive indicator of a very poor drinking water status.

Commonly, when coliform bacteria are present, there is a high risk that other infectious bacteria and viruses may also be present in the water. Potentially dangerous microbiological contamination can easily occur in any Horses drinking water. For instance, water polluted by the urinary excretion of Leptospira by rodents can cause abortion in mares and the death of foals.

Horses are also sensitive to toxins produced by Cyanobacteria (often called blue-green algae because they are similar to algae in habitat, morphology and photosynthetic activity). They are a component of the natural plankton population in healthy and balanced surface water supplies. They are found as single cells or in clumped or filamentous colonies. Cyanobacteria can move vertically through water by adjusting their buoyancy in the water column. Cyanobacteria only become a potential hazard when they are present in large numbers (blooms). Blooms typically occur on warm days with light to calm winds, in waters of neutral to alkaline pH containing elevated levels of inorganic phosphorus and nitrogen, although blooms at other times are possible. It is recommended that water contaminated with these algae ‘blooms’ should be seriously avoided. Cyanobacteria poisoning in domestic livestock may cause photosensitisation, sudden death, weakness, bloody diarrhoea, tremors, and convulsions. After post-mortem, clumps of algae may be found in the gastrointestinal contents of animals that die suddenly.

Nowadays however, most if not all harmful bacteria and algae can be easily destroyed and removed by the installation of a filtration and purification system to the Horses drinking water supply that includes an Ultra Violet Steriliser (UV); this treats the water supply flowing through it with high levels of Ultra Violet Light at such high frequencies; it destroys any organic life-form. Please telephone Aquatec Rainsoft Ltd: ++44 (0) 117 910 9988 for more details.

The affects of Antibiotics, Chlorine, Chloramines and Stress on the Gut Flora and Fauna

Broad-spectrum antibiotics and some anti-parasitic chemicals periodically introduced into the Horse’s digestive system because of illness or infection, sometimes devastate the beneficial bacterial gut population as well as the intended target pathogens. Frequent occurrence of a repeated disease following antibiotic treatment suggests a protective and suppressing effect from the normal resident population. This normal gut flora and fauna acts as an important barrier to pathogenic colonisation by monopolising all available nutrients and residential sites in the gut ecosystem. Some are also able to produce their own antibodies against other species. For example, various lactobacillus strains produce lactic and acetic acids and hydrogen peroxide which inhibit the growth of Escherichia coli and other gas producing coliforms which cause disease when their colony numbers become excessive.

After any course of antibiotics, a course of probiotics should be considered to renew the Horses gut flora and fauna (please take advice from your own Horse Vet). It has been found by certain equine research groups that a course of probiotics improves the fermentation process in the hind gut (large intestine) that indicates that these ‘good bacteria’ can be beneficial in stabilising digestive disturbances. Because these digestive disturbances result from carbohydrate ‘overload’, caused when the Horse is fed concentrate feed or the gut flora and fauna has been disrupted (such as after a course of antibiotics, high levels of stress, or continued contamination of their food and/or drinking water). It has also been shown that these ‘overloads’ can bring out colic and laminitis in some individuals.

Laboratory experiments have also shown that Horses that have a reduced gut flora and fauna have much weaker immune systems than those with a normal collection of gut flora and fauna, which can be demonstrated by phagocytic activity and lowered immunoglobulin levels. Recent findings show that Lactobacilli (a probiotic) given orally can stimulate immunity in a nonspecific way, which demonstrates many more areas of potential health benefits that can now be derived from probiotics. It seems that not only do they have the ability to affect the balance of the gut flora and fauna, but they could also influence various diseases, which can occur in tissues other than the intestinal tract.

The use of probiotics is more for prophylactic medicine rather than for use in a disease therapy. Pathogens that cause disorders are usually well established by the time the symptoms show, and providing an abundance of beneficial microorganisms at this stage is consequently unlikely to be as effective as the present antibiotic strategies that are well tried and well known.

Stress is also a major factor in the Horse’s life, which will also disrupt the gut flora and fauna. Stress can be generated by any drastic change in the physical or emotional environment – birth, weaning, travelling or even just plain fear. The optimum pH for the growth of the beneficial bacterial species in the gut flora and fauna in a Horse is a pH of 6 – entirely different from the pH needs of most pathogens – which is generally a pH of 8 to 9 (remember, the pH scale is logarithmic NOT linear). The imposition of stress on the Horse can result in an increase in this intestinal pH and therefore, hugely favours the development of pathogens. When this occurs, the number of for example Lactobacilli decreases whilst the numbers of Coliforms can increase.

Chlorine and/or Chloramines in the water, which can be added by the water supply company to act as a purifying, antibacterial agent, will also have a detrimental effect on the Horse’s beneficial gut flora and fauna. There is also some anecdotal evidence that suggests a beneficial improvement to the Horse’s skin and coat can be seen over the short term, by the removal of Chlorine and/or Chloramines from the Horses drinking and general use stable water.

Drinking Water and General Stable Water Purification/Filtration Systems for Horses

The technical level of the general filtration and water purification of the drinking and general stable water for Horses has today reached high levels of expertise. It is nowadays common practise for the almost complete removal of Nitrates, Chlorine and Chloramines, bacterial pathogens and algae; whilst changing the water quality itself to the beneficial TDS and pH levels that the Horse requires for maintaining health and a sound overall condition.

Aquatec Rainsoft Ltd of Bristol, UK have been designing and building specialist water purification systems for Horses for years; please telephone ++44 (0) 117 910 9988 for more details. Aquatec Rainsoft Ltd’s purification systems come as ‘complete’ integrated systems that ‘liquid engineers’ your local water supply to the Horses unique requirements by passing the water supply through various designs of pressure vessels that contain novel filter media. These media either remove or destroy any organism or harmful chemical compound that may be present. These processes run side by side with the ability of these systems to alter the water quality itself regarding the pH and TDS level to suit your Horse’s unique metabolism.

With the levels of chemical compounds and organic pathogens increasing in the general tap water supply as well as most groundwater supplies – on a yearly basis, it should be seriously considered whether an Aquatec Rainsoft Ltd Integrated Water Purification System may be beneficial to your Horse’s health and wellbeing.

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