Apart from air, water is the most important nutrient for all forms of life, including dairy cattle. Not having a safe and reliable water supply can significantly reduce dairy cow and calf health along with milk production. Water is necessary in a wide array of bodily functions at both the extracellular and intracellular levels. Key roles include physiological maintenance such as electrolyte balance, osmotic regulation and thermoregulation. Water is necessary for the excretion of urine and feces as well as growth, pregnancy and lactation. Water is necessary for proper rumen function and digestion.

Dairy farmers spend much of their time focusing on feeding their cows correctly. Feedstuffs – forages, grains and commodity byproducts – are routinely analyzed for their nutritional content. All this time and energy is spent on dozens of feed ingredients – vitamins, minerals, protein and energy – but the word “water,” the most important nutrient of all, is seldom mentioned in the discussion of a dairy cow diet. Ironically, dairy farmers often do not know how much water their herd should consume or the quality of the water that’s being consumed.

High-producing cows will consume 30 gallons or more per day in conditions with mild temperatures and low humidity. In hot and humid conditions, they will need 50 gallons of water per day. Lactating dairy cows require 4.5 to 5 pounds, or roughly one-half gallon of water, for every pound of milk produced. Even a small limitation in water intake will decrease dry matter intake by 1 to 2 pounds daily, which can limit peak milk production by 2 to 5 pounds – directly affecting dairy profitability.

Cows don’t need a lot of time to drink water. One study showed that they can do all their drinking in about 30 minutes throughout the day. However, when they do need to drink there should be lots of water available. When given the opportunity, cows tend to alternately consume feed and drink water. Ideally, fresh, clean water should be available to the cow whenever she consumes feed. So providing easy access to water for cows and heifers is important in making sure they get enough water to drink during a day.

Water that’s contaminated with pollutants or is high in antagonistic minerals can be just as problematic as not getting enough water. A common sign of poor water quality and intake includes depressed feed intakes, which leads to depressed milk production. Poor water quality may result in depressed immune function, leading to poor conception and or abortions. Digestive upsets resulting in diarrhea in cows or scours in calves can be caused by contaminated water. If water sources cause digestive upsets in humans, there’s a good chance that the water is not well suited for animals, either.

Observation of cows drinking – especially when they initially put their nose in the trough or waterer – will give an idea of how palatable the water is. Any hesitancy by the cow or heifer to drink will be a clue that there’s something not right with the water such as palatability, odor or temperature. Water with excessive solids from dirt can hinder cows’ desire to drink. However, on most dairy farms, the water that’s used in the troughs and barns on the dairy comes from the same source as water used by owners and employees – so in most cases problems with water quality are corrected fairly quickly when humans are required to drink it.

Solids and minerals that are present in water may interfere with proper vitamin and mineral metabolism. High concentrations of sulfate, chloride, iron, manganese and nitrates are known to significantly affect animal health and production. Excessively high levels of any of these can affect taste and palatability as well as upset nutrient balances due to antagonisms or toxicity.

A dairy diet may be balanced for a certain level of mineral, for instance sulfur, but excessively high levels of sulfate in the drinking water will result in an excessive level of sulfur, which, due to their atomic similarity, may limit proper absorption of copper, another critical mineral in the diet, resulting in a copper deficiency. Particularly in close-up dry cow diets where the anionic balance is critical for proper calcium uptake at the time of freshening, excessive levels of some sulfates or chlorides may result in diets that are overly anionic. Excessive levels of iron are known to affect the taste of water as well as limit a cow’s ability to metabolize vitamin A. Water that’s excessively alkaline (high pH) can cause alkalosis in cows with diets that contain high levels of buffers such as sodium bicarbonate.

Problems with water quality and quantity are more likely to arise in remote locations of dairy farms or ranches where small or shallow wells cannot provide adequate water for a herd or the cattle are forced to drink from mud holes or intermittently flowing brooks or streams. Water testing for the dairy should include analysis for total dissolved solids, bacterial levels, pH, hardness, nitrates and toxic compounds such as polychlorinated biphenyl or hydrocarbons if there is a known history of pollution in the area. Most of the time, if the water is safe for humans, it’s safe for animals.

Throughout the dairy and near the feeding areas, cows should have unrestricted access to waterers or water troughs. There should be access to water near the exits of milking parlors since cows are known to also prefer water soon after they have been milked. Watering troughs should be large enough to allow a number of cows to drink at the same time without crowding. Watering troughs should be cleaned routinely. In regions of the country where water freezes during winter it’s important to keep water free of ice so that drinking is not limited in the cold environment.

Both the economic and health implications of water consumption and water quality are often overlooked on dairy farms. The availability and importance of water should not be taken for granted. Not having enough water or settling for poor quality water can be a costly mistake.