As dairy producers enter fall and winter, everyone is concerned with adjusting dairy cow rations to accommodate this year’s hay and corn silage crops. It is critical to adjust and tweak rations to ensure high milk production and maintain key milk components (i.e., milkfat and protein). However, did you know that by focusing only on things like dry matter intake, protein, carbohydrates, effective fiber, minerals, etc., you are only accounting for about 12 percent of the cow’s total nutrient intake? Why? A milking cow drinks 30 to 50 gallons of water per day; therefore, water accounts for about 88 percent of a cow’s daily intake of nutrients. Thus, water is the most important nutrient in a cow’s total daily intake.

I would encourage every dairy producer to have their cow’s drinking water analyzed at least twice each year. The water table waxes and wanes especially in times of drought like many dairy producers experienced this year. Therefore, getting your cow’s drinking water analyzed should be a high priority item at the top of your management checklist. There are many private laboratories that can perform such analyses. To find a suitable laboratory just do an internet search for “drinking water analysis laboratories”. Most labs sell the entire drinking water analysis kit that contains sample containers, instructions and a prepaid box to send the sample back to the lab. When requesting the water analysis, be sure to specify a “livestock suitability” water analysis. Midwest Laboratories in Nebraska and  Litchfield Analytical Services in Litchfield, Mich.,  are two labs you may want to consider, though there are many others out there which also offer livestock water analysis.

A sound livestock drinking water analysis will at least contain the following four items:

  1. Total Dissolved Solids (TDS): TDS measures the sum of all inorganic matter dissolved in water and is an indicator of water salinity. Levels above 1,000 parts per million (ppm) should be investigated further and potentially be corrected to prevent and/or correct problems like diarrhea and dehydration.
  2. Sulfate + Chloride: If the combined sulfate (SO4) and chlorine (Cl) content of drinking water is greater than 500 ppm, further testing and evaluation are needed. At these, or higher levels, these minerals may lead to health and production problems.
  3. Nitrate-nitrogen: Nitrate-nitrogen (NO3-N) levels in drinking water should not exceed 20 ppm. 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.
  4. Iron: Cattle drinking water containing over 0.3 ppm iron may cause subclinical chronic iron toxicity, or even more severe problems. Most dairy rations provide adequate iron. Thus, when drinking water contains excess iron (soluble iron called ferrous-iron in drinking water); the total iron may rise in the cow’s tissues causing “oxidative stress”. This may lead to a host of problems including increased retained placentas, mastitis, metritis and a general compromising of the animal’s immune system. Excess soluble iron in the animal’s gut also ties-up and reduces absorption of other key minerals such as zinc and copper.

Table 1 provides a summary of the most important items to consider in a livestock water analysis along with the levels of these constituents that warrant a retest or require action to correct. Also, excess content of these mineral constituents in water may also contribute to problems with your farm’s water delivery system (i.e., pumps, pipes, valves, etc.) and decrease the effectiveness of cleaners and sanitizers (e.g., pipeline cleaning and sanitizing). The latter could lead to milk quality problems (e.g, increased bacteria counts) and buildup within pipes that lead to chronic milk quality problems and restrict water flow. A livestock water analysis costs less than $50 per sample, but provides important information that may provide the key to top health and production for your dairy herd.

Table 1: Actionable levels of important water constituents (1, 2, 3)




 Total Dissolved Solids   (TDS)

>500 ppm


 Sulfate (SO4), +   Chloride (Cl)

>250 ppm

>500 ppm

 Nitrate-nitrogen (NO3-N)

>10 ppm

>20 ppm

 Iron (Fe)

>0.15 ppm

>0.3 ppm


<6.5 or >8.0

<6.5 or >8.5