CowsLivestock Water Requirements

Livestock and poultry require large quantities of water to survive and perform to their maximum potential. For optimal livestock performance, the water source should be not toxic and palatable enough to encourage animals to drink optimal amounts.

Total Dissolved Solids (TDS)

“Total dissolved solids” (TDS) refers to the amount of salts dissolved in water and is expressed in milligrams per liter (mg/L). TDS is the sum of all the salts dissolved in water including sodium, chloride, magnesium, sulfate, carbonate, bicarbonate, phosphate, etc. Because some salts are more toxic than others, it is not recommended to use TDS values alone to determine suitability for livestock health. Table 1 shows general guidelines for TDS concentrations, but it is best to use this table in conjunction with other parameters such as sulfate. TDS can be estimated with “electrical conductivity” (EC) using a simple handheld meter. The meters function based on the fact that pure water does not conduct electricity, it is the salts dissolved in water that conduct.

If an EC meter gives a conductivity value greater than 5 mS/cm or a TDS value greater than 3,000 mg/L, consider testing the water for sulfate with either a test strip or by sending a sample to a lab.

Total Dissolved Solids

(Electrical Conductivity)

Animal Response

Less than 1,000 mg/L

(EC < 1.5 mS/cm)

Relatively low in salinity. Excellent for all classes of livestock and poultry.

1,000-2,999 mg/L

(EC 1.5 to 5 mS/cm)

Very satisfactory for all classes of livestock and poultry. May cause temporary and mild diarrhea in livestock not accustomed to the water.

3,000-4,999 mg/L

(EC 5 to 8 mS/cm)

Satisfactory for livestock, but may cause temporary diarrhea or be refused at first by animals not accustomed to the water. Poor water for poultry.

5,000-6,999 mg/L

(EC 8 to 11 mS/cm)

Can be used with reasonable safety for cattle, sheep, swine, and hors-es. Avoid use for pregnant or lactating animals. Not acceptable for poultry.

7,000-10,000 mg/L

(EC 11 to 16 mS/cm)

Considerable risk for pregnant or lactating cows, cattle in confinement, horses, or sheep or young of these species. In general, should avoid use. Unfit for poultry and probably for swine.

More than 10,000 mg/L

(EC > 16 mS/cm)

Extremely high risk. Not recommended for use under any conditions.

Note: To estimate TDS from EC, multiply the EC (in units of mS/cm) value by 650.


In Montana, high TDS values are often a result of high sulfate levels, which have a recommended intake limit of 1,000 mg/L for long‐term (chronic) exposure. High sulfate levels interact with copper and molybdenum and can lead to poor performance or increased incidences of polioencephelomalacia (PEM), a brain disorder. Livestock can adapt to high saline water but abrupt changes from low to high salinity water can be harmful. Test strips for sulfate are available and can provide rough estimates of sulfate concentration.


Cyanobacteria, traditionally called blue‐green algae, is actually a bacteria. When large blooms of these bacteria grow in a water source, they can release toxins. Cyano‐ bacteria blooms can be fatal to livestock and other animals if large amounts of infected water are ingested. Symptoms of cyanobacteria toxin poisoning in livestock range from: acute to severe diarrhea and/or vomiting, weakness, staggering, or convulsions.

Green algae and aquatic plants do not produce toxins and can be identified by filaments or visible leaf structures. A simple test is to dip a stick into an algae bloom. Green algae will droop off the stick, while cyanobacteria will coat the stick, more like paint.

Additional Parameters of Potential Concern






1 mg/L

There is not evidence that arsenic below 1 mg/L is toxic to livestock.



100 mg/L

Concentrations below 100 should be protective. Nitrate levels in forage and water should be considered together and dry diets high in NO3 may require lower concentrations.



0.1 mg/L

Concentrations under 0.1 should be protective. Signs of selenium poisoning include excessive salivation, shallow breathing, breath odor, diarrhea, vomiting, spasms, and death from respiratory failure



1,000 mg/L

Concentrations under 1,000 should be protective. Values above 5,000 can cause serious effects and death. Short term exposure should not exceed 4,000.



1,000 mg/L

Concentrations under 1,000 should be protective. There is a high risk of acute death at concentrations above 3,000. Risk of polio or death increases dramatically above 2,000.

Additional Resources

Montana Harmful Algal Bloom website

North Dakota State University, Livestock Water Quality

University of Wyoming Extension, Water Quality for Wyoming Livestock and Wildlife, Raiseback et al. 2008, B1183:

South Dakota State University, Interpretation of Water Analysis for Livestock Suitability, 2008 

Agriculture and Agri-Food Canada, Water Quality Impacts on Livestock 

Livestock Water Quality, Olkowski, 2009, University of Saskatchewan