April 9, 2002

Poor water quality can jeopardize dairy cow health, limit milk production

An average dairy cow drinks about 25 gallons of water each day. But she'll drink less if water quality is poor. And that will limit her milk production and jeopardize her health, according to Jim Linn, dairy scientist with the University of Minnesota Extension Service.

Linn recommends getting livestock drinking water analyzed for coliform bacteria and other microorganisms to determine its microbial quality. "Highly contaminated water exposes cattle to disease-causing organisms," says Linn. "Microorganisms can contaminate water in wells. However, bacterial contamination is much more likely to occur in the drinking vessel, so keeping water troughs clean is a must."

Treating water to remove or reduce contaminants can be expensive and may require significant equipment maintenance. Therefore, Linn recommends laboratory analysis of the drinking water before making a decision to treat. He says treatment needs to be cost effective and bring about known health or production benefits for the cattle.

Ray Hozalski, water treatment expert in the U of M Department of Civil Engineering, says the best treatment option for livestock drinking water depends on the target contaminant. Eliminating disease-causing microorganisms involves disinfecting the water. The most common chemical disinfectant used is chlorine, a powerful oxidizing agent that's inexpensive and effective at low concentrations. A sufficient dose of chlorine provides a residual that can continue to destroy bacteria after the treatment process. The effectiveness of chlorine disinfection is determined by the product of the chlorine concentration and the contact time. Therefore, chlorine usage typically requires a contact tank that allows the chlorine time to disinfect the water prior to consumption.

A non-chemical disinfection process uses ultraviolet light. Hozalski says the effectiveness of UV irradiation as a disinfectant depends on the ability of the UV light to pass through the water and contact microorganisms. Therefore, UV irradiation may be ineffective for cloudy or colored water. Also, UV light doesn't provide residual disinfection.

Distillation, reverse osmosis and ion exchange are treatment methods for removing or reducing nitrate, sulfate and minerals in water.

Distillation and reverse osmosis remove water contaminants and essentially demineralize the water, says Hozalski. During distillation, water is boiled to form steam. The steam is captured, cooled and condensed to re-form liquid water. Nitrate, sulfate and all other minerals are removed, as they remain in the boiling tank. Distillation is not commonly used for water treatment because of the high cost of heating water.

Reverse osmosis removes nitrate, sulfate and other minerals by forcing the water through a semi-permeable membrane at high pressure. The dissolved minerals remain behind on the feed side of the membrane, creating a concentrated brine solution. Treated water is often blended with bypassed or untreated water to achieve the desired mineral composition.

Ion exchange systems can decrease nitrate, sulfate, water hardness and total dissolved solids. The systems have an exchange column filled with ion exchange resin, a waste storage tank and a regeneration solution tank.

Two concerns that are common to reverse osmosis, ion exchange and distillation are the high cost of setup and operation of these systems and the disposal of the concentrated waste stream. Thus, the decision to install such a treatment system should consider both the economics and the brine disposal issues.

A U of M publication entitled "Water Quality for Livestock and Poultry" has additional information. It's available at a nominal cost from county offices of the U of M Extension Service. Ask for item AG-FO-01864. It can also be ordered from the Extension Distribution Center with a credit card by calling (800) 876-8636 or (612) 624-4900.

Web,V2,A4,D1 linn0325

Sources:  Jim Linn, (612) 624-4995; Ray Hozalski, (612) 626-9650
Editor:     Joseph Kurtz, (612) 625-3168, jk@umn.edu

NOTE: News releases were current as of the date of issue. If you have a question on older releases, use the news release search (upper left-hand column of the News main page) or the main Extension search (upper right of this page) to locate more recent information.

URL: http:// www.extension.umn.edu/extensionnews/2002/PoorWaterQualityCanJeopardizeDairyCowHealth.html  This page was updated May 21, 2002 .
Online Privacy Statement.  Contact Information.

University of Minnesota Extension is an equal opportunity educator and employer.
Copyright  ©  Regents of the University of Minnesota.  All rights reserved.