Dairy cows need lots of good water

By Jim Linn, University of Minnesota Extension

ST. PAUL, Minn. (2/16/2009)—Water is the most essential of all nutrients required by animals. And a lactating dairy cow has one of the largest requirements for water of any animal.

This is because 56 to 81 percent of her body weight is water and she needs to replace the major loss of water through milk production (milk is 87 percent water). So it's essential that dairy cattle drink adequate quantities of water each day to meet their requirements. Drinking water is the primary source and method of meeting the daily water requirement; the water in feed makes a small contribution towards the daily requirement.

A frequent comment on dairy farms where water quality problems are suspected is "cows are not drinking enough water." Cows will consume water in direct proportion to their physiological needs (milk production, maintenance, growth and gestation) and dry matter (DM) intake. There is no evidence to suggest cows will "luxury" consume water above their needs or that increasing water consumption beyond requirements will stimulate DM intake and/or milk production.

So the challenge in diagnosing dairy farm production problems is determining if milk production is being limited by the quantity and/or quality of water consumed; or if milk production is limited by other factors and cows are drinking to meet milk production requirements.

Here are some key points regarding water and minerals:

• Cows only spend about 12 to 15 minutes per day drinking water. The highest water intake periods are immediately following milking and during feed consumption.
• Cows consume water to meet their requirement. Limiting water intake by restricting access to or reducing consumption because of poor quality will decrease milk production. However, milk production and feed intake can't be stimulated by offering good quality water and enhancing water consumption above the amount needed to meet current milk production requirements.
• The mineral constituents found in water that have been shown by research to affect animal performance are: total dissolved solids (TDS), sodium chloride, sulfur (sulfate), and nitrate. Iron and manganese have been indicted in many water quality problems, but research directly linking iron and manganese to reduced water consumption and lowered milk production is lacking.
• Calcium, magnesium and water hardness are not believed to affect water intake or performance of animals.

Any use of this article must include the byline or following credit line:
Jim Linn is head of the Department of Animal Science at the University of Minnesota.

Media Contact: Catherine Dehdashti, U of M Extension (612) 625-0237, ced@umn.edu

URL: http:// www.extension.umn.edu/extensionnews/2009/dairy-cows-need-good-water.html  This page was updated Feb. 16, 2009 .
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