Only air is more important than water to dairy cows. When one considers milk is 87% water and lactating cows typically drink four to five lb of water for every pound of dry matter consumed, it is easy to see why cows not only need good-quality water, but why they also need an abundant supply.

Determining if a Water Problem Exists
Signs that water quantity or quality may be limiting animal performance include:

• Firm manure

• Low urine output

• Infrequent drinking

• Considerable, unexplained drop in milk yield

• Difficulty in raising calves on milk replacer

• Cattle drinking urine

Other considerations that point to a potential water problem include:

• Is low milk production the result of low water intake or is low water intake the result of low milk production?

• Do people drink the same water as livestock?

• Does water have a bitter or off-flavor?

• Do people and livestock suffer frequently from diarrhea?

• How do cattle respond to alternative water sources?

• Do newly arrived cattle seem slow to adapt or do poorly?

• Are clogged pipes or low water pressure a problem on the dairy?

Assessing Water Quantity
Due to space limitations, this article will focus primarily on water quality. However, when evaluating a water system, it is important to answer the following questions:

• Is water supply adequate?

• Is volume adequate to meet peak demands?

• Is there adequate waterer space (2 ft of accessible waterer per 10 to 20 cows)?

• Are water devices and water accessible?

• Does a boss cow limit access of a submissive cow to the water trough or drinking cup?

• Are waterers clean?

Assessing Water Quality
Research studying the effect of water quality on animal performance is limited. This may partially explain why upper desired and maximum levels for minerals in water vary. In addition, tolerable levels of minerals in water vary depending upon the following factors:

• Animal age (milk replacer fed calves are less tolerate of poor-quality water than weaned calves)

• Physiological state (lactating cows are less tolerant of poor-quality water than non-lactating animals)

• Performance level (high producing cows are less tolerant of poor-quality water than low producing cows)

• Climate

• Ration moisture level

• Ration mineral levels

In addition, cattle are more tolerant of poor-quality water if they are gradually adapted to poor-quality water than cows abruptly switched to poor-quality water. In this article, water quality relating to minerals, bacteria (coliform, E. coli, and fecal coliform), and nitrates will be discussed.

Minerals
In the United States, iron (Fe), manganese (Mn), sulfur (S), calcium (Ca), and sodium (Na) are a concern. In Pennsylvania, 35, 25 and 20% of samples exceeded the upper desired level for manganese, iron, and sulfur, respectively. Please note this survey of mineral content of water did not examine heavy metals such as cadmium or radionuclides, or other elements such as fluoride, bacteria, and blue-green algae.

Water containing high levels of iron and manganese may reduce water intake, can stain equipment, buildup in pipes, restrict water flow, and reduce life expectancy of water softeners and hot water heaters. Water high in iron and manganese increase the risk of iron and manganese bacteria that produce red-brown or black-brown slime that can clog equipment and pipes. The upper desired level for iron and manganese in water is 0.2 and 0.05 ppm, respectively. In a survey of 36 water samples collected in south central Pennsylvania, 50% of samples exceeded the upper desired levels for iron.

Table 1 lists the effect of the source of iron and manganese in water on treatment options.

Table 1 Effect of Source of Iron and Manganese in Water on Treatment Options
Problem	Cause	Treatment
When drawn, black or red-brown particles appears as water stands; staining of fixtures	Dissolved Fe and Mn	–      Phosphate compound (<3 mg/L ppm Fe) –      Water softener (<5 mg/L, Fe + Mn) –      Oxidizing filter (Mn greensand or zeolite) (<15 mg/L Fe + Mn) –      Aeration (pressure) (<25 mg/L Fe + Mn) –      Chemical oxidation with potassium permanganate or chlorine, followed by filtration (>10 mg/L Fe + Mn)
Contains red-brown or black particles when drawn and settle out as water stands	Iron particles from corrosion of pipes and equipment	Raise water pH
Contains red-brown or black particles when drawn; particles settle out as water stands	Oxidized Fe/Mn due to air exposure prior to tap	Particle filter – if quantity of oxidized material is high, use larger filter (sand filter) rather than in line filter
Red-brown or black slime appears in toilet tanks or form clogs in faucets	Fe or Mn bacteria	Disinfect supply by shock treatment with  chlorine or potassium permanganate, then filter; bacteria originating in well, continuous feed of chlorine or potassium permanganate, followed by filter
Reddish or black color that remains longer than 24 hours	Colloidal Fe/Mn organically complexed Fe/Mn	Chemical oxidation with chlorine or potassium permanganate, followed by filtration; mechanical aeration not recommended as Fe/Mn bacteria or Fe/Mn complexes will clog filter

Table 2 provides treatment options for water high in iron and manganese.
 

Table 2 Options for Treating Water High in Iron and Manganese
Treatment	Noteworthy Points
Phosphate treatment	–   Works in pH range 5 to 8 –   Must be added close to well head, before Fe and Mn are oxidized –   Fe and Mn not removed, retains metallic taste –   Too much phosphate and water may feel slimy –   Treated water is not heat stable, heated water (i.e., water heater) will break down phosphate compound and release Fe and Mn –   Increases phosphate content of water
Chlorine oxidation	–   Water pH needs to 6.5 to 7.5 to oxidize Fe, not method of choice for Mn as pH needs to greater than 9.5 for complete Mn oxidation
Potassium permanganate	–   Oxidizes Mn at pH 7.5 or higher, more effective for iron oxidation if organic iron is a problem –   Poisonous and a skin irritant

Bacteria, Coliform, Fecal Coliform, and E. coli
Upper desired levels for bacteria, coliform, and fecal coliform numbers are 1000, 0.5, and 0.1 per mL, respectively. In a summary of 94 samples collected from south central Pennsylvania, 25% of water samples exceeded the upper desired level for coliform.

Causes of high bacteria and coliforms in water include:

• Cracked or pervious well casings (such as those found in old or hand dug wells)

• Septic systems or feed lots draining towards the well

• Poor seal on well allowing insects, rodents, and animals to enter the well

• Flood waters contaminating the well

• Contamination during system repair

Several methods can be used to reduce bacteria levels in water. Some of these methods are listed in Table 3, along with advantages and disadvantages of each method.
 

Table 3 Advantages and Disadvantages of Different Water Disinfection Methods
Method	Advantage	Disadvantage
Chlorination	-    Provides residue disinfectant -    Residual easy to measure -    Relatively inexpensive -    Treats large volumes of water; -    Treats multiple problems (H2S, Mn, Fe, bacteria)	–   Requires up to 30 minutes contact time –   Cloudy or dirty water reduces effectiveness –   Adds a chlorine taste –   Chlorine handling and storage issues –   Less effective at cold water temperatures or high pH
UV light	–   Does not change taste or odor of water –   Kills bacteria almost immediately –   Compact and easy to use	–   High electrical demand –   No disinfection residual –   Requires prefiltering of cloudy/colored water –   Requires routine cleaning of tube; high mineral water will coat lamp sleeve –   Requires replacing lamp annually

Ultraviolet light and chlorination systems are less effective if water is cloudy. Chlorination systems fail if equipment is not functioning properly or if systems are not properly calibrated or contact time is limited.

Figure 1 shows the amount of residual chlorine needed to disinfect is directly affected by the amount of contact time (longer contact, less chlorine needed) and by water pH (the higher the pH, the more chlorine needed).

Nitrates
Nitrates are another common water problem. The upper desired and maximum level of nitrate-nitrogen in water is 20 and 100 ppm, respectively. In 70 samples collected in south-central Pennsylvania, 5% of samples exceeded the upper desired levels for livestock. Research has shown that high nitrates in water affect animal performance. Cows consuming high nitrate water produce less milk and have poorer reproduction than cows consuming low nitrate water. It should be noted that cows will be less tolerate of high nitrate water when consuming feeds high in nitrates.

Sources of nitrates in ground water include:

• Nitrogen fertilizer

• Animal waste

• Crop residue

• Industrial waste that leaches through the soil

Nitrate levels tend to be highest in shallow wells and following a very heavy rainfall or in spring of the year following snow melt.

Table 4 lists advantages and disadvantages of different methods to treat high nitrate water.
 

Table 4  Advantages and Disadvantages of Different Methods to Treat High Nitrate Water
Method	Advantages	Disadvantages
New water source	Easiest method to handle high nitrate water	–      Expensive, may also be high in nitrates –      May not have access to low nitrate water
Distillation or reverse osmosis	Removes nitrates and all minerals from water	–      High energy input –      Low yield, RO, ½ to 1/3 of water is waste –      Disposal of waste water/residue
Anion exchange	Treat large quantities of water	–      Capacity reduced in high sulfate water –      Water will be more corrosive –      Disposal of nitrates

Concluding Points

• Producers should sample water at least once a year to determine water quality and track the results. Water should be analyzed for mineral, nitrate, and bacteria content.

• Producers should proceed with caution before installing water treatment equipment. Consider bringing a high-quality alternative water source onto the dairy. This will help producers determine if their current water source is truly a problem. Cows should respond favorably to the new water source within 10 to 14 days.

• Response to a new water source could be less if there is a buildup of material in pipes from the old water source. Try to deliver the water from the alternative source to cows using a new pipe or pipe that has been thoroughly cleaned.

• Bringing an alternative water source on the dairy may be difficult and/or expensive. However, the cost of water treatment equipment is expensive, especially if it doesn’t fix the problem!

• Sometimes water has multiple problems (nitrates, bacteria, etc.), and one piece of equipment may not provide a solution to all problems. In some cases, multiple pieces of equipment, such as an anion exchange unit to remove nitrates and a UV light system to kill bacteria, may have to be installed to correct the problem.

• Water treatment systems need to be properly sized. If the system is not large enough to treat water for the herd or restricts water flow to the cows, benefits of the water treatment system will be minimal.

• Finally, water treatment systems need to be properly maintained according to manufacturer’s recommendations to obtain maximum benefits.

Water is the nutrient required in the second largest quantity, second only to air. Providing cows with ample amounts of fresh, clean, high-quality water is one way dairy producers can capture the maximum benefits from the herd’s genetic and feeding programs.