Water quality for dairy cattle


Source: Ministry of Agriculture, Food, and Rural Affairs

Fact Sheet written by: T. Wright – Dairy Cattle Nutritionist/OMAFRA


Water is the most important nutrient for dairy cattle. Dairy cattle need free access to a clean, quality source of water for optimal production. Water intake is affected by factors such as environmental temperature, ration dry matter content and milk production. A high-producing lactating dairy cow can drink over 150 litres of water on a hot day. One important, but often overlooked, aspect of nutrition is the quality of water – this might include the presence of potential contaminants, the ultimate levels of these contaminants, and most importantly, the impact they have on the cow’s water intake.

There are 5 criteria to consider when assessing water quality including:

  • odour and taste
  • physical and chemical properties
  • presence of toxic compounds
  • concentration of mineral compounds
  • microbial contamination (e.g., bacteria, protozoa, viruses).

For some criteria there are a range of acceptable levels in water but generally a maximum acceptable concentration guideline is given.

There are various international guidelines related to water quality for livestock. These guidelines sometimes disagree because of differences between experts in the interpretation of information used to determine maximum acceptable limits. Differences in risk perception and the extrapolation of human water quality guidelines to dairy cattle when specific data are scare are two reasons for disagreements in guidelines.

The following information was taken from several sources including the Canadian Water Quality Guidelines for Livestock (Task Force on Water Quality Guidelines, 1987); Livestock and Water Quality(Agriculture and Agri-Food Canada, 2000), Nutrient Requirements of Dairy Cattle (NRC, 2001), Water for Dairy Cattle (New Mexico State University, Guide D-107), and Water Quality and Pig Performance (OMAF Factsheet Order No. 91-071). Where guidelines from these sources conflicted, the one specific to dairy cattle was used; otherwise, the lowest concentration guideline was used. Guidelines for water quality are affected by other factors including environmental, nutritional, and physiological, which make it difficult to accurately determine at what concentration of a contaminant a particular problem will always arise.

This Factsheet provides details on water quality guidelines for dairy cattle with an emphasis on mineral compound concentrations, salinity (or Total Dissolved Solids), and bacteria. Other critical considerations for providing water to dairy cattle such as trough space, water flow rate, placement and type of watering devices, and cleanliness are not discussed.

Physical Characteristics and Mineral Guidelines

A list of minerals, mineral compounds or physical/chemical characteristics with the maximal acceptable concentration (or acceptable range) for dairy cattle is shown in Table 1.

Discuss concentrations of minerals or physical characteristics above the levels described on the next page with a nutritionist. Excessive minerals in water can affect the availability of other dietary nutrients and can contribute to digestive, health, and performance problems. In some cases an adjustment to the dietary ration may be necessary (e.g. very high sodium water).

Table 1. Maximum Acceptable Concentrations of Minerals, Mineral Compounds and Physical Properties1

Generally Considered Safe Upper Limit Concentrations in Water for Dairy Cows
Alkalinity (as CaCO3)A
Antimony A
Barium A
Beryllium A
Boron A
Calcium ions A
1,000 (700 if magnesium present)
Cobalt A
Copper A
Flouride A
2 (1 if present in feed)
No limit established
Iron A
0.3 (not a toxicity guideline)
Magnesium A
0.05 (not a toxicity guideline)
Mercury A
Molybdenum A
PH (pH units) A
Selenium A
Sulphate A , D
Sulphide (H2S) A
<1 (taste and smell advisory, not toxic guideline)
Tin A
Titanium A
Uranium A
Vanadium A
Zinc B

1. Reported in parts per million (ppm; equivalent to mg/litre) unless otherwise noted.

A. Agriculture and Agri-Food Canada. Livestock and Water Quality (2000).

B. National Research Council. Nutrient Requirements for Dairy Cattle (2001).

C. Water hardness has not been documented to limit water intake of dairy cattle. Soft water is considered to be 0-60 mg/L, moderately hard water 61-120 mg/L, hard water 121-180 mg/L, and very hard water >180 mg/L. Water hardness is predominantly contributed by calcium and magnesium and is often reported in equivalent amounts of calcium carbonate (CaCO3).

D. The chemical form of sulphate or sulfur should be determined when concentrations in water exceed 500 ppm. Hydrogen sulfide is a toxic form and concentrations of 0.1 ppm can limit water intake. High concentrations of other sulphates (e.g. sodium sulphate, magnesium sulphate) can have laxative effects.

Nitrate and nitrate-nitrogen

Dairy cattle can use nitrate present in water as a source of nitrogen in the rumen for microbial protein synthesis. Reduction of nitrate to nitrite can also occur. Nitrite is harmful to cattle because it reduces the oxygen carrying capacity of blood and, in severe cases, can result in death. Nitrite at low concentrations is toxic to humans. Dairy rations should be evaluated for nitrates when a problem with nitrite is suspected because the combination of nitrate from water and feed is additive.

Table 2. Nitrate and Nitrate-nitrogen Water Concentration Guidelines for Cattle.

Nitrate (NO3) (ppm)
Nitrate-Nitrogen (NO3-N) (ppm)
Safe for dairy cattle
Safe with balanced diets, low nitrate feeds
Potentially harmful over long-term
Cattle at risk, potential death
Unsafe for cattle

From National Research Council. Nutrient Requirements for Dairy Cattle (2001).

Total Dissolved Solids (Salinity)

Total dissolved solids measures salinity of water from a variety of compounds that are soluble in water. The primary contributor is sodium chloride (table salt), but other chemicals including bicarbonates, sulphate, magnesium and calcium contribute as well. Ranges of salinity are given in Table 3. Generally, salinity (total dissolved solids) below 3,000 ppm is considered safe for dairy cows.

Table 3. Salinity (Total Dissolved Solids) in parts per million (ppm).

Low salinity level; no health problems
Generally no problems; possible temporary diarrhea to animals not accustomed to this water
Water intake not maximized; initial refusal; temporary mild diarrhea
Avoid for pregnant and lactating cattle
Saline water; should not be fed to cattle; poor production and/or health problems

From National Research Council. Nutrient Requirements for Dairy Cattle (2001).

Bacterial Contamination

Bacterial contamination of water is measured in a laboratory using microbiological techniques to permit any bacteria present in a water sample to grow. Results are then counted and reported as bacterial counts per 100 mL of water. A coliform count over 1/100 mL can cause scours in calves. In adult cows, a count of 15-20/100 mL can cause diarrhea and cows may go off-feed. Positive results for fecal coliform (more than 0 counts/100 mL) indicate a pollution problem that should be investigated and corrected.

Taste and Odour

Ontario producers should contact the Ministry of the Environment (MOE) for help related to taste and odour concerns. Regional MOE offices are listed in the blue pages of your phone book. If the water quality problems are a natural characteristic of the aquifer (e.g. high iron or sulphate levels) you may be referred to a commercial lab or private water treatment consultant. For suspected pollution problems (e.g. seepage from a nearby landfill site) MOE will take water samples from the farm for analysis.

Water Testing

Ideally, a water test would be done about four times a year to accumulate seasonal information for the aquifer used by the farm. Commercial testing rates vary depending on the analyses conducted by the different laboratories. A list of laboratories can be obtained from OMAFRA. Note: The Ministry of the Environment only tests water when a problem is suspected. Commercial laboratories conduct routine water testing.