Editor's note: Jennifer Swim, of J.E. Swim Dairy Consulting in Cambridge City, Ind., handled the following case study. It was reported in the April 2009 edition of Nutritionist e-Network and is being repeated here because it carries such a good message.

An 80-cow herd in Ohio experienced some problems that took a bit of detective work to solve.

It was a good, registered Holstein herd that typically had been at 23,000 pounds. But production dropped off to 18,000 pounds. And, the fresh cows were having too many problems with metabolic disorders, such as ketosis and milk fever.

"The cows just didn't look right," says herd nutritionist Jennifer Swim. "Hair coats were not good, eyes were not bright."

The owners had been having some health problems of their own. That, along with moving the cows into a new barn, gave everyone a chance to come up with some really good excuses for why the cows weren't performing as well. But at one point, everyone agreed, "We just can't use those excuses anymore. We have to check everything."

They looked at the ration first, but really couldn't find any fault with it.

"This farm does a good job of making quality feeds," Swim says. Everything gets mixed well with a TMR mixer.

Due to careful observation (and part intuition), they noticed that cows weren't drinking from the water troughs as readily as they should be. Again, they had to adjust for the new barn. The old barn only had one water trough; the new barn had several. It just didn't seem like there were many cows at any given trough.

They took water samples and sent them to a lab. The samples came back showing high iron levels.

Swim went on the Internet to learn more about water with high iron content. She came across a paper that David Beede, dairy nutritionist at Michigan State University, had delivered a year or two earlier at the Mid-South Ruminant Nutrition Conference. In it, he talked about water quality and some of the "anti-quality" factors that may be present. He mentioned that palatability can suffer with high iron levels, as well as actual intake through the formation of slime by iron-loving bacteria.

"I called Dr. Beede and he was very helpful," Swim says. Among other things, Beede had information about water-treatment systems.

Initially, Swim's approach was to chlorinate the well water with Clorox. And, it did seem to help: The cows responded with 3 more pounds of milk per cow per day. But Swim was cautious about putting too much Clorox in over time because it might harm the pumping equipment. And, she wanted a more-permanent solution than simply dumping some Clorox in the well every couple of days. Several of her other clients already had a hydrogen-peroxide system for killing bacteria in the water. It was simple to install, with an injector pump at the well. And, it cost less than $500.

Things have improved with a hydrogen-peroxide system in place. The cows are drinking more water and they are "much, much healthier," Swim says. The herd average is climbing, she says. It's now at 19,500 pounds — up significantly from the 18,000 pounds experienced while the water problems were occurring. In retrospect, bacteria in the water inhibited water consumption, which could explain why milk production was lagging when dry matter intake was so excellent.

"I hypothesize that the cows actually were eating so much because they were thirsty. But without adequate water intake, they were not able to properly digest the ration and capitalize on their high dry-matter intake," Swim says.

The experience has sharpened her focus on the importance of water. Certainly, if she sees cows that are producing below their expected levels (based on dry matter intake), she will check the water. But before taking water samples and sending them off to a lab, she will check the management aspects, such as sanitation and making sure there is enough space for the cows at the waterers.

"I think we take water for granted," she says.