Expert Answers - Aug. 15, 2008

Answer provided by Dave Beede, professor of dairy nutrition, nutrient and environmental management at Michigan State University.


Q: How much iron are your clients supplying to cows through the drinking water each day?

A: Hopefully, not too much! Excess iron in water causes iron toxicity and is a major problem in some dairies across the country. In this time of high input costs, excess iron and subsequent poor cow performance can be the business-breaker. Fortunately, excess iron in drinking water is relatively easy to detect with a standard laboratory analysis. Then corrective action can be taken.

The recommended maximum tolerable concentration of iron in drinking water is 0.3 ppm (parts per million). Concentrations in excess of this can be a major detriment to normal health and performance of dairy cows, and a significant health risk for humans. A cow producing 100 pounds of milk requires about 35 milligrams of absorbed iron daily, commonly supplied in her ration. However, if she consumes drinking water with 0.3 ppm iron (versus no iron in water) her total absorbable iron intake doubles. If the drinking water contains 0.6 ppm iron, then total absorbable iron intake is three-fold the dietary requirement. I’ve seen many laboratory analyses of drinking water from dairies where iron concentrations are 1, 2, 3,……even as high as 8 ppm.

Typically, in most rations there is plenty of total iron to meet the cow’s absorbed iron requirement, even though dietary iron is very insoluble in the digestive tract of adult cattle and only about 10 percent absorbable. The common chemical form in feeds is ferric iron, Fe⁺³. In contrast, iron in drinking water is highly soluble and nearly 100 percent absorbable (ferrous iron, Fe⁺²). So, major problems result from high iron in water.

Excess iron in drinking water can lead to cellular oxidative stress and inhibit copper and zinc absorption. Oxidative stress results in damage to cell membranes and disrupts normal physiological functions and biochemical reactions. It is suspected that consequences of excess iron and heightened oxidative stress are magnified in transition and fresh cows with compromised immune function, increased fresh cow mastitis and metritis (excess ferrous iron in the body enhances the potential for bacterial infections), greater incidence of retained placentas, diarrhea, below normal feed intake, and reduced growth and milk production.

To my knowledge, there are no controlled research studies quantifying animal responses to excess iron in drinking water or removal of that iron. Nonetheless, anecdotal evidence from several field cases in the last several years suggests marked improvements in milk yield and cow health when excess iron is removed from drinking water.

Also, high iron in drinking water may reduce water intake because it is unpalatable (less acceptable). This directly reduces feed intake and milk production. Also, the dark reddish brown slime formed by iron-loving bacteria in water troughs may affect water intake and even the rate and volume of water flowing through pipes. To my knowledge, it is not known if these iron-loving microorganisms directly affect the digestion, metabolism, or physiology of cows. But, anecdotal experience suggests that treating drinking water to eliminate these microbes improved milk yield and health of cows.

If high-iron (> 0.3 ppm) drinking water is present, an alternative water source with lower iron concentration should be found. Or, a method to remove the iron from water before consumption by cattle and humans should be used.

Water-treatment options

Excess iron in drinking water can be removed by one of several water-treatment methods. The most common treatment methods to remove water-soluble iron include:

• Chlorination when followed by mechanical filtration or an activated carbon filter.
• An ion-exchange system, especially when iron concentrations are less than 1.0 ppm.
• Ozonation.
• Reverse osmosis.
• An oxidizing filter.

Whatever the most appropriate treatment method to remove iron from drinking water, here are some recommendations on how to proceed to a solution if one suspects high iron in drinking water.

1. Take a water sample as described at the Internet link listed below.

2. Have a standard laboratory analysis done by a certified laboratory.

3. If the laboratory reports iron concentrations >0.3 ppm, take two more samples and send each to a different certified laboratory for iron analysis. This may seem like over-kill, but a treatment system is a sizable investment, so it is important to know for sure that iron concentration is in excess.

4. When collecting samples for laboratory testing, take and label two more samples to save as back-ups and a historical record.

5. If iron is in excess, contact two or three water treatment companies and ask about their treatment methods, and if and how they remove iron from water. Local or regional companies are often best to ensure good customer service and maintenance after installation. And, here are some questions to ask prospective water-treatment companies:

• Do you know how much water this particular dairy uses? Obviously, the company representatives will not know this, but you’ve got to know the answer to this question! Most dairies use a lot of water; often much more than companies are accustomed to treating at a single location. What is the treatment rate (volume/time)? Can their system supply enough water for all functions on the dairy simultaneously during peak usage (e.g., during milking, parlor clean-up and when cows are drinking)? Will a sizable investment in large long-term storage of the treated water be necessary to ensure that you have ample supply during peak usages?
• Does each company guarantee that their system will remove iron? Are they willing to provide a written guarantee that their system will remove iron throughout the specified life of the treatment system?
• How long will the systems last and how much maintenance is required? Who does the maintenance? Do they have “service-after-the-sale” and what does that entail? Do they have or can they provide a maintenance contract?
• Which other anti-quality factors (besides iron) do their water treatment systems remove? There may be none. But, there also may be additional benefits to one treatment system over another if other constituents are in excess in water samples.
• What chemicals (e.g., other mineral elements) does their particular treatment method add to the water and what will be their concentrations? There may be nothing added. But, in other cases something may be added, such as significant chlorine during chlorination.
• And, obviously what do the systems cost ? installation, and monthly maintenance and operating costs?

6. After a treatment system is installed, take treated water samples at least every month, label and tightly seal them, and store in a cool place for historical purposes. At least every third month send a sample to a certified laboratory for a standard analysis, including iron. Is the water-treatment system removing iron as guaranteed?

For guidelines on how to take a drinking-water sample and standard water analysis, click here (PDF format).

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