Water Usage on Dairy Farms

Dr. Maurice Eastridge, Extension Dairy Specialist, The Ohio State University

As we always say "water is the most important nutrient", but all too often it is the most ignored nutrient when we are thinking of nutrition and animal performance. However, it is the first target when environmental risks are being addressed. Therefore, we must constantly monitor water quality and quantity on dairy farms for animal health and performance and for protecting the environment.

About 80% of the water intake by animals is from drinking and other 20% is consumed via the feed. The amount provided by the feed depends on how much of the diet consists of silage and wet commodities (e.g. wet brewers grains). Animals can not go without water for very long, but it is important to recognize that younger animals are at greater risk for dehydration from water deprivation than older animals; the younger the animal the greater proportion of the body that is water (range for body water content is 70 to 50% for cattle). Lactating dairy cows will respond quickly to problems with water availability and quality, but the most immediate response will be a drop in milk yield (milk consists of 87% water). In a lactating cow, about 24% of the daily water intake is secreted in milk, 12% is in the feces, 10% is excreted in the urine, and the remaining 54% may be lost via evaporation and the extent of water loss by evaporation is highly dependent on environmental temperature and humidity in the animal's living environment (in other words, not just based on the readings from the outside wall of the barn). Typical water intakes are provided in Table 1.

Table 1. Water intake by dairy animals (gallons/day, unless noted otherwise).1

Dairy Animal
Air Temperature
Heifer, 300 lb
Heifer, 900 lb
Cow, dry, 1400 lb
Cow, lactating, maintenance2

1000 lb


1400 lb

Cow, lactating, milk production, gal/lb 4% fat-corrected milk2

1Taken from Linn, Four-State Dairy Nutrition Conference, 1991, pg. 80-96.
2The intake for maintenance and milk production must be added together for total daily intakes.

Intake of water by animals is also dependent on its availability. Generally, it is recommended that 2 linear ft of water space be available for every 20 to 25 cows. The floor surface around the waterers should not discourage animals from approaching them and need to be placed in multiple locations in large sections of free stalls so cows do not crowd around them and so the cow will not have to walk very far to get a drink. Cows usually are thirsty after leaving the parlor, so a water trough should be placed in the return alley from the parlor to the housing area. Oftentimes, this is the trough that water from the plate cooler will be discharged into. Cows drink by sucking water into their mouth, so they should place their nose in the water to get a drink. If you see an animal lapping water, this is abnormal and stray voltage should be suspected. The waterer should be routinely cleaned; tip tanks work extremely well for easy cleanout - the opposite are the water bowls with the floating balls that hide the filth in the bowls.

Water intake and the animal's performance can be affected by the quality of the water (Table 2). Water can be analyzed at many different laboratories in Ohio (see fact sheet located at http://ohioline.osu.edu/aex-fact/0315.html). Water treatment options do exist, but these are usually quite costly considering the available technology and the quantity of water used on a dairy farm. One of the first approaches to dealing with water concerns in addition to chemical analysis is determining water intake. This can be most effectively done on most dairy farms by placing a meter in the water line (see related article in this issue of Buckeye Dairy News) or by placing a water tank in the facility and recording the amount filled and amount drank by the animals. Sometimes if quality is a problem, locating an alternative source may be the most favorable option (i.e. digging a new well, changing from surface water to a well, or in some cases, using a municipal water source). Well heads should be adequately set back from animal lots and the ground surface should slope away from the well head to prevent surface water from running down the well casing.

Table 2. General guidelines for water quality for animals.

6.8 - 7.5
May affect intake
  ---------------------- ppm --------------------
1 - 250
May reduce Cu and Se absorption
Sulfate sulfur
0 - 83
May reduce Cu and Se absorption
Ca or Mg
0 -200
Usually not a problem, but really high levels may decrease intake
0 - 300
High levels reveal the use of a water softener
0 - 0.3
May decrease water intake; look for red stains on surface of water holding vessels
Nitrates (NO3)
< 20
Nitrites (NO2)
< 10
Coliform bacteria None (0 counts) for potable water; <1000 fecal counts/ 100 ml tolerated by adult animals

Water usage on dairy farms also includes that for cleaning the parlor, holding pen, and milking equipment (possibly up to 17 gal/cow/day), and in some cases, for flushing the alleys in the free stall barns. Water from cleaning and any water that comes into contact with manure becomes, by definition, manure. Therefore, it is important to minimize runoff from cow lots by having them under roof and by placing gutters on buildings so the water can be diverted away from coming into contact with the manure. Manure storage should provide at minimum for six months of capacity, but given the typical weather conditions in Ohio, 8 to 12 months of storage capacity is recommended. Other areas of focus for reducing environmental risks pertaining to water is capturing the seepages from silos and making sure that animals do not have direct access to streams.

Water is an extremely valuable natural resource. The amount needed on dairy farms should be planned, availability and quality for animals continually monitored, and risks for contamination be minimized.