For decades, the guidelines for Fe in drinking water for dairy cattle suggested that 0.3 ppm was a level at which palatability would become an issue. This level was based on human palatability guidelines. In the February 2013 Journal of Dairy Science, David Beede finally provided some much needed data in this area. View abstract here.
In those studies, Dr. Beede examined both the level and form of Fe in water and the effects on water intake. What they found is that somewhere between and 4 and 8 ppm, cows will back off of water intake, presumably because of taste.
The form in which Fe was added to the water made no difference. Both ferrous (Fe+2) and ferric (Fe+3) sulfate or chloride were tested at 0 or 8 ppm of Fe, and water intakes did not differ between forms. Similarly, ferrous sulfate, ferrous chloride and ferrous lactate were tested at 8 ppm of Fe. Again, there was no effect of the form of Fe in the water on intake.
One aspect which was not addressed in these experiments was the role of Fe oxidizing bacteria which will proliferate in water pipes and troughs when there is sufficient Fe in the water to support their growth. It is not known whether these bacteria are toxic in any way, but they may play a role in reducing palatability and hence, water intake.
Subsequent posts will address some options for removing Fe from water if it seems to be a problem.