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What if cows don't drink enough water?

Neil Broadwater, Regional Extension Educator-Dairy

Published in Dairy Star October 19, 2007

What happens if a lactating cow doesn't drink enough water? If the question is a joke, the answer could be, "you will get evaporated milk or dried milk powder." If it's a serious question, the answer will be "you will not get optimal milk production and health can be adversely affected."

The amount of water a cow drinks depends on her size and milk yield, quantity of dry matter consumed, temperature and relative humidity of the environment, quality and availability of the water, amount of moisture in her feed and the sodium, salt and protein content of the diet. If your cows have inadequate water intake, you may see signs showing up such as firm, constipated manure; low urine output; infrequent drinking; high packed-cell volume or hematocrit in blood; dehydration from toxins; and/or fever.

Pounds of water intake (1 gallon of water weighs 8.32 pounds) can be predicted using the following equation (Murphy et al., 1983), used for the 2001 NRC recommendations:
35.25 + 1.58 x dry matter intake (lb/day) + 0.90 x milk yield (lb/day) + 0.11 x sodium intake (grams/day) + 2.65 x weekly mean temperature (degrees F divided by 1.8 minus 17.778)

This equation predicts that water consumption will change 1.58 lb for every 1 lb of milk produced, 0.11 lb for each gram of sodium consumed, and 1.47 lb for each degree F change in the weekly mean temperature. The following table shows the estimated daily water intake for a 1,500 lb lactating cow (assumes sodium intake at 0.18% of dry matter).

How do you measure actual water consumption? The best way is to install an in-line water meter at each water source. Measure the water intake for at least 5 to 10 consecutive days. Be sure to determine daily feed intake for those same days and determine the moisture content of the feed so the water intake from the feed source is discounted when estimating water intake.

What are some possible causes of cows not drinking enough water? One of the main reasons can be because it is too crowded around the waterers, or the waterers are not delivering the water fast enough. Penn State researchers (Adams and Sharpe) reported water intake may be limited by: 1) a lack of supply or drinking devices or restricted flow from corroded valves, pipes clogged from iron-bacteria slime or scale; 2) low chemical quality such as very acidic, very alkaline, hydrogen sulfide (rotten egg odor), metallic taste from iron, manganese, sulfates; high total dissolved solids content; 3) pollution -- from high total bacteria counts (most common); coliform from fecal or non-fecal sources; 4) bad taste; 5) algae (especially blue-green type); 6) sites of contamination -- water source, pressure tank, reservoir, drinking device (feed or manure).

If you find that milk production has dropped dramatically, it is time to take action and evaluate the water supply.

1. Flow Rate. Cows should never have to wait for water to be available. There must be enough tanks, troughs, or fountains to enable most cows to drink relatively soon after milking or eating. Use valves that permit 15 gal/min of flow at 20 lb pressure. For stall barns, the types and valves of drinking cups for dairy cows need to be relatively trouble-free.

2. Watering Space. According to Michigan State University researchers, a minimum of one watering space or 2 ft of tank perimeter for every 15 to 20 cows is recommended. Provide 2 ft of linear trough space per cow in return alleys or breezeways from the milking parlor. Cows will line up side by side and drink, just like they do at the feed bunk, and they like to have sufficient space to back away from the trough after drinking. Cows drink 50 to 60% of their total daily water intake immediately after milking. Head clearance around water troughs should be at least 2 ft on every side. Water troughs should be an optimal height of 24 to 32" (2 to 3" less for Jerseys). Water depth should be a minimum of 3" to allow the animal to submerge its muzzle 1 to 2". However, water depth should be no more than 6 to 12" in order to prevent stagnant water, for ease of cleaning, and for rapid filling so cows never have to wait to consume water. Waterers should be within 50 ft of the feed bunk or at every crossover in the freestall barn. Make sure there is no dead end alley where the water source is located, as can be the case in some remodeled freestall barns. For grazing operations, water should be located at the milking parlor exit and in each paddock so that animals are always within 600 ft of clean, fresh water sources.

Water quality issues for the lactating cow

If water is highly contaminated, dairy cattle are exposed to disease-causing organisms. If the drinking water has an offensive odor and taste, dairy cattle can detect it. If the water smells or is unpalatable, cows may not drink enough to meet production needs or it could even be completely refused. So, if health and production problems are showing up in the herd, the quality of the water should also be investigated and analyzed for coliform bacteria and other microorganisms.

Here are some items to consider:

  • Bacteria counts - According to Looper (New Mexico State) and Waldner (Okla State), in their publication "Water for Dairy Cattle," total coliform count should be under 15/100 ml. Fecal coliform counts should be under 10/100 ml. Total bacteria counts in excess of 500/100 ml may indicate water quality problems. Water sources with total bacteria counts in excel of 1 million/100 ml should be avoided for all livestock classes.
  • Clean waterers - Bacterial contamination most often occurs in the waterers. Cleaning water sources such as drinking cups, bowls and tanks routinely (daily, every 2 days, weekly) is very important.
  • Water temperature - Cows prefer to drink water with moderate temperatures (63-82°F) rather than very cold or hot water, if given a choice.
  • Check for nitrates - Nitrate sources can come from fertilizers, animal waste, fecal material, crop residue. Nitrate poisoning results from a bacterial reduction of nitrate (NO3) to nitrite (NO2) in the rumen [conversion is: nitrate nitrogen (NO3-N) x 4.43 = Nitrate (NO3)]. The nitrite absorbed into the blood can reduce its oxygen carrying capacity.
    • Total dissolved solids (TDS) or salinity - The summation of all inorganic constituents present in water. It is a measurement of the amount of sodium chloride, bicarbonate, sulfate, calcium, magnesium, silica, iron, nitrate, strontium, potassium, carbonate, phosphorus, boron and fluoride in water. Research indicates that high levels of TDS combined with increased environmental temperature have a detrimental affect on milk production. Water containing <5,000 ppm may be fed to lactating cattle, but >7,000 ppm is unacceptable for all cattle, according to the 2001 National Research Council guidelines.
    • pH level - A guideline for pH of water has not been established due to a lack of research determining the effects of water pH on water intake, milk production and dairy cattle health.
    • Blue-green algae - Cattle should be prevented from drinking water with heavy algae growth. Symptoms in blue-green algae poisoning include ataxia or in-coordination of voluntary muscle movement, bloody diarrhea, convulsions and sudden death. This is an occasional problem in freestanding water, such as farm ponds.
    • High iron, manganese, or molybdenum content may increase needs for copper, or result in more iron-bacteria problems. Iron concentrations in drinking water of greater than 0.3 ppm are considered a risk for human health, and are a concern for dairy cattle health and performance. The first concern is that high iron in drinking water may reduce the palatability (acceptability) and, therefore, consumption. Also, a dark slime formation in plumbing and waterers formed by iron-loving bacteria may affect water intake and even the rate and volume of water flow through pipes (Beede, "Assessment of Water Quality and Nutrition for Dairy Cattle").
    • Water sampling and testing - Take 1 or 2 quarts of water from the source in question. Send samples to any accredited commercial or state operated laboratory for analyses. Consult with your herd veterinarian for assistance in selecting a laboratory as well as for assistance in selecting appropriate tests and interpreting test results.
    • Any water treatment needs to be cost effective and bring about health and/or milk production benefits. Dairy farms use large volumes of water and treatment systems must be sized to fit the need. Reverse osmosis and ion exchange are treatment methods for removing or reducing nitrate, sulfate and minerals in water, but there is a high cost of setup and operation of these systems.

    Further information on water quality for dairy cattle can be found at

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