If the combined sulfate + chloride content of dairy cattle drinking water is greater than 500 ppm, further testing and evaluation are needed (1, 2). At higher than recommended levels, these minerals may lead to health and production problems. For example, some have observed that high levels of sulfate + chloride cause diarrhea and dehydration in calves, plus increased retained placentas and displaced abomasums in fresh cows (1).
Nitrate-nitrogen levels in cattle drinking water should not exceed 20 ppm (1, 2). High nitrate-nitrogen levels have been associated with long-term reproductive problems in dairy cows, such as higher services per conception, lower first service conception rates, and longer calving intervals (5).
If dairy cattle drinking water contains over 0.3 ppm iron cows may suffer from iron toxicity. Iron in drinking water is in the ferrous state (Fe2+) and is soluble, odorless, and easily absorbed in the animal’s gut. However, most dairy rations provide more than adequate iron which is in the less absorbable ferric state (Fe3+).
This form of iron is converted in the animal’s gut to ferrous iron (Fe2+) and absorbed for use by the animal’s tissues. When drinking water contains excess ferrous iron (Fe2+) this may lead to excess ferric iron (Fe2+) in the animal’s tissues causing “oxidative stress” where cell membranes lose integrity. This can lead to increased retained placentas, mastitis, metritis, and a general compromising of the animal’s immune system (2, 4). Problems related to depressed immune function are more likely to show up in transition and fresh cows, reducing peak milk yield.
High iron in drinking water also may depress water intake due to palatability issues although this is not well understood (4). Excess soluble iron (Fe2+) in the animal’s gut also reduces absorption of other key minerals like zinc and copper (4). In addition to the problems these various water constituents may cause to cattle health and performance they also may contribute to problems with your farm’s water delivery system e.g., pumps and pipes) and the effectiveness of pipeline cleaning and sanitizing.
This could in turn lead to increased bacteria counts and buildup within water pipes restricting water flow. For example, high iron levels in water encourage the growth of iron bacteria that plug pipes and coat pumps and other water system components with a slick, rust-colored slime.
How Should You Address Water Quality Issues?
First, you should test your cattle’s drinking water on a quarterly basis for TDS, sulfate, chloride, iron, and nitrate-nitrogen (4). Second, you should check to make sure your dairy facility’s water delivery system meets guidelines for number of waterers, space, location, and cleanliness .