Water is probably the most over-looked nutrient, notes Mike Socha, research nutritionist with Zinpro Corporation. While much attention is given to supplying adequate amounts of water and offering cows plenty of room at the water trough, very little is given to the composition of the water they drink.

Recently, Socha and colleagues summarized the results of a nationwide water analysis project that sheds more light on the composition of water, particularly its mineral content.

The findings show that the mineral content of water in the U.S. varies dramatically within a region — and even within a dairy — and could very likely impact palatability and mineral intake by your cows.

To arrive at these findings, several nutrition consultants and feed companies across the country contributed 3,618 water samples that had been analyzed for several minerals — calcium, iron, magnesium, manganese, sodium and zinc, for example — as well as pH and total solids content. Then, Socha and colleagues at Zinpro Corporation and the University of Minnesota summarized the findings.

The results show that each mineral, except zinc, exceeded the upper desired level for livestock in at least one or more of the 3,618 samples. For example, of the 2,423 samples analyzed for iron, 969 of the samples — roughly 40 percent — contained excess iron. The average water sample analyzed for iron contained about 0.79 parts per million (ppm) of iron — that’s 0.59 ppm more than the recommended level for livestock. This increase in iron — not to mention other minerals — can reduce palatability, and consequently, water intake. And that, in turn, can reduce milk production.

Besides identifying high levels of minerals in the water samples, the analysis also showed the mineral content can vary considerably within an area. In California, for example, the amount of sodium found in water samples collected in one local area ranged from 46 ppm to 559 ppm. At the high end of the spectrum, the water contained 509 ppm more sodium than recommended for livestock. In fact, almost 50 percent of the samples taken from that area exceeded desired sodium levels.

In addition, the analysis showed that the mineral composition of water can even vary within the water supply for a dairy. For example, on dairies where at least four samples were collected, the average iron content of the water ranged from a minimum of 0.13 ppm to a maximum of 1.39 ppm. Some of the variation can be explained by the fact that samples were collected from multiple sources on the dairy. However, the fact that this much variation existed within a dairy is eye-opening.

While there is little research on the impact of water mineral variation on animal health and performance, excess minerals in water can decrease palatability and water intake. It also can increase the amount of minerals a cow consumes. If, for example, your water contains about 56 ppm of chloride, that adds 0.03 percentage units of chloride — about 7.9 percent chloride — to a cow’s total chloride intake. “On the high end, it could contribute a substantial amount of chloride” — 0.33 percentage units of chloride or roughly 48.5 percent — to the cow’s total chloride intake, Socha notes.

Thus, you should monitor the mineral content of your water on a routine basis. Doing so can be helpful for diagnosing water intake problems and even balancing your ration.

“Water analysis is part of a good overall management program,” Socha says. Look for additional information on this nationwide water analysis in an upcoming issue of Dairy Herd Management.