Countless horse supplements and feeds exist, each claiming to be the “best,” the “optimum,” “your assurance of maximum performance” or featuring a slogan like “insurance for perfect health.”

These nutritional supplements and feeds seem to assume that the most important horse nutrients are always found in adequate supply and are of sufficient quality.

What is the horse’s most important nutrient? Water! Good old-fashioned clean, pure water; no magic elixir, no synthetic performance enhancing substance. Just water. 

Water Vs. Energy

Some 60 to 80 percent of the daily nutritional intake of horses is represented by water, which accounts for 70 to 73 percent of the animal’s total body mass. A horse’s requirements for water are proportional to the animal’s energy consumption.

As farriers know, water requirements increase above normal levels during exposure to hot environments. This increases water loss through the animal’s sweating and panting.

For a horse, drinking water actually has a higher priority than eating. Horses that voluntarily eat normal amounts of feed usually have satisfactory water intakes.

Since water quality directly affects liquid consumption, and since the first effect of voluntary or involuntary water restriction is to reduce the feed consumption and thus performance or growth efficiency, the importance of a good supply of high quality water becomes essential. If a horse doesn’t eat the suggested amount of a particular feed or ration, various nutrients — including those required for proper hoof growth and function — will be in shorter supply than intended. 

Cheap Yet Essential

horse and bucket

WATER PRIORITY. For a horse, drinking water actually has a much higher priority than eating. Horses that eat normal amounts of feed usually also have satisfactory water intakes.

Most horse owners turn on the tap and expect a never-ending supply of clean, fresh, pure, potable water. Water has been one of our least expensive resources and one many of us take for granted. As seasons and rainfall levels change during the year, the quality and content of the horses’ water supply often change.

This is especially true when a horse’s water supply is derived from surface sources or shallow wells less than 50 feet deep. In fact, the reason that horses undergo various health problems can often be tied to fluctuations in water content.

Hooves are living tissue that contain high amounts of various nutrients, including water. If horses become dehydrated, it’s difficult to keep the hooves flexible and properly nourished. Besides the obvious problems associated with a lack of water, one of the most overlooked problems with water is the potential for interactions with other essential nutrients.

Besides being essential, water often contains minerals that are required by horses. The actual contribution of a mineral found in a water supply to the overall nutritional requirement for that particular mineral depends on the specific concen- tration, its chemical form and the amount of water that is consumed. Important considerations must be made between the mineral’s interaction with other minerals found in water and various feedstuffs.

Water can contain an endless number of chemicals, micro-organisms and dissolved or suspended particles that may impair performance.

The following sections attempt to define common water analyses in relation to horse performance, potential mineral interactions and the impact on hoof quality and growth.


Water hardness is generally expressed as the sum of calcium very hard water should be identified.

High calcium ties up zinc. Excess calcium and magnesium causes a decrease in the absorption of phosphorus. Excess magnesium decreases absorption of calcium, replaces calcium levels in bones and increases calcium excretion. Excess calcium and phosphorus decrease the absorption of manganese and its utilization. High calcium levels reduce fluorine absorption and can affect iron utilization. Excess calcium can also reduce the absorption of copper and iron. 


Iron may occur in water as ferrous bicarbonate, which is colorless when dissolved. But as soon as the water is withdrawn from the well and comes in contact with air, the iron oxidizes and turns into an insoluble ferric hydroxide. Carbon dioxide is a byproduct of this process. High dietary iron levels can decrease performance parameters in many animal species.

High levels of iron may reduce copper, cobalt, magnesium, selenium and zinc utilization, leading to deficiencies of these minerals. Iron overload increases the risk of infection and neoplasia. High iron content also often results in decreased water consumption.

pH Levels

The pH has little direct effect on the acceptability of water for a horse, unless the pH level is extreme on either end of the spectrum. However, the pH level can have a major influence on the chemical reactions involved in water usage or on the corrosive nature of the water. 

High pH impairs the efficiency of chlorination, while low pH (below 6 or 6.5) may lead to an increase in some antibacterials. Acidic water can cause chronic acidosis problems when offered with some rations.

The pH of water also affects the occurrence of urinary calculi. More alkaline water leads to more skin conditions, bacterial infections and enteric problems, especially in young foals. Alkalinity usually promotes the growth of bacteria and may lead to increased amounts of scale in water pipes and heaters.


From this brief description of potential water mineral interactions, you can see the potential for decreased hoof integrity. This can be caused by the water tying up important hoof nutrients and the resulting decreased bioavailability or deficiencies that result.

For example, zinc is so crucial for proper hoof development and function that it is easy to see how hard, iron-filled water can prevent zinc from reaching the hoof in proper quantity for optimum hoof health and function.

Hoof supplements often contain zinc in a form that doesn’t allow proper absorption when subjected to hard, iron-filled water. As a result, the horse owner essentially wastes money and their horse eventually suffers from “bad feet.”

Your shoeing clients need to know that buying expensive hoof supplements with pretty containers and impressive marketing materials is no substitute for knowing the mineral content of their water supply. That’s because the minerals present in their water can lead to troublesome interactions when using some hoof supplements.

Interrelationships Are Critical

All dietary nutrients (minerals, vitamins, amino acids, energy sources, etc.) are interrelated to some degree. As a result, there’s an optimal nutrient level for each nutrient in relation to all others to obtain the most efficient desired animal response.

The impact of mineral interrelationships represents an increasingly complex research problem for horse nutritionists. Before the research is complete, any horse caretaker can assure the best possible nutrition by being more educated about all nutrient inputs.

This includes water, the horse’s most important nutrient.

Dr. Gary Pusillo is the owner of INTI Service Corporation in Marshalltown, Iowa, a consulting company that deals with equine nutrition concerns around the world. This article was inspired by a recent trip that Dr. Pusillo made to Brazil and Argentina where poor water quality has destroyed the hoof integrity of many horses.