Water Quality and Quantity is Critical

Water is often neglected when looking at the feeding and management of a dairy operation. It is, however, the most important nutrient we provide the cow and nothing will result in a more immediate drop in milk production than a decrease in water consumption. Consider this. A cow producing 100 lbs of milk will lose over 25 gallons (200 lbs) of water in milk, urine and feces. Introduce heat stress and this number can increase by 50%. The amount of water a cow will drink depends upon her production and the environmental temperature. On average, dairy cows can be expected to drink 4 lbs water (0.5 gallons) for every lb of milk produced. Heat stress, and diets high in salt, sodium bicarbonate and buffers will increase water consumption.

Maximizing water intake will help cows maintain good production. Place water bowls close to feeding areas to encourage the cows natural preference to drink after eating. Water temperature does not have a significant effect on milk production although cows prefer to drink non-chilled water (17-28ºC). In one study, cows lined up waiting for a chance to drink the non-chilled water rather than drink the chilled water. Chilled water may, however, be more desirable during times of heat stress because of its cooling effect. Increasing flow rate into water bowls increases water consumption while decreasing the number of trips cows make to the water bowl. Check for stray voltage which can limit water consumption. Provide a minimum of one water bowl for every 10 cows.

Providing good quality water to dairy cows is a must. Information on water analysis (sampling techniques, labs) can be obtained from your local ag. rep office. Guidelines for interpreting water analysis results are outlined below.

Total Dissolved Solids (TDS)

TDS in water is comparable to RFV and forages – it provides an overall evaluation of water quality in a single number. A TDS value less than 1000 mg/L means the water is safe for any livestock. Avoid use of water with TDS greater than 3000 for dairy cows.

Hardness (mg/L CaCO3)

Water with more than 121 mg/L as CaCO3 is considered hard. This does not raise health concerns but the mineral content can lead to the accumulation of scale and clogging of pipelines and drinkers. This may decrease water consumption.

Sodium (Na in mg/L)

Water with over 800 mg sodium/L can cause diarrhea and a drop in milk production. High sodium levels (over 250 mg/L) may necessitate adjustments to the feed ration (ie. removal of dietary salt).

Sulphates (SO4 in mg/L)

Water for calves should contain <500 mg/L while water for adult cows should contain <1,000 mg SO4/L. Sulphate levels above 2,000 mg/L can cause diarrhea and reduced milk production. Because sulphates can bind with copper reducing its availability, dietary copper levels will need to be increased if water is high in sulphates.

Iron (Fe in mg/L)

Iron levels over 0.3 mg/L can reduce water intake and production. As little as 0.1 mg/L may contribute to oxidized flavour problems in milk.


Water pH is generally between 6.5 and 8.5. Values less than 5.5 may lead to acidosis and reduced feed intake.


Nitrates are usually reported as “nitrate- and nitrite-nitrogen combined”. Water for dairy cattle should contain less than 10 mg NO3-NO2-N/L. Water with 10-20 mg/L can generally be used in balanced diets with low nitrate feeds. Consumption of water containing over 100 mg/L of NO3-N02-N/L can be fatal. High water nitrates are generally a result of runoff from livestock yards and heavily fertilized fields.


Water may contain a variety of microorganisms, including bacteria, viruses, protozoa and parasite eggs. A coliform bacteria count of over 1/100 ml can cause scours in calves. A count of over 20/100 mg can result in diarrhea and off-feed problems in cows. Fecal coliform counts should be less than 1/100 ml for calves and less than 10/100 ml for cows.

For further information contact:

Karen Dupchak
Farm Production Extension, Animal Nutritionist
Manitoba Agriculture Food, and Rural Initiatives
204-545 University Crescent
Winnipeg, MB R3T 5S6
Phone: 204-945-7668
Fax: 204-945-4327