Agriculture, Trade and Consumer Protection

Mark A. Cook
Wisconsin Public Service Commission

Roger Kasper
Wisconsin Department of Agriculture, Trade and Consumer Protection


Introduction:
Concern about the influence of stray voltage on Wisconsin dairy farms has commonly focused on
water. Data from 285 stray voltage investigations in Wisconsin found that 50% of the farmers indicated
reduced water intake as one of the symptoms that led to their concerns about stray voltage.
1
Experience
gained from over 800 farm visits as the veterinarian with the State of Wisconsins Rural Electric Power
Services Program (REPS, previously the Stray Voltage Analysis Team or SVAT) has proved that water is
one of the more contentious issues on dairy farms where there is a concerned about stray voltage.
a

Working with water issues during farm investigations has revealed that among rural professionals
serving dairy farmers there is widespread deficiency in the understanding of how to determine water intake
and how stray voltage affects water intake. In addition, there is a significant lack of scientific knowledge
about how most aspects of how water quality may affect intake, health, or performance in dairy cattle. This
combination increases the vulnerability of dairy farmers to be given misinformation about water. The most
disturbing manifestation of this is when the lack of rural expertise on water issues allows enterprising
individuals to profit from farmers who are already economically stressed.
In this article consideration will be given to the understanding of water consumption, the
relationship of stray voltage to water intake, the interpretation of atypical behaviors associated with water
sources, and water quality as these issues relate to dairy cattle.

Water Consumption:

The science of water consumption in dairy cattle is well documented. The National Research
Councils Nutrient Guidelines for Dairy Cattle (NRC) contains multiple formulas usable for the prediction
of free water intake in lactating and dry cows, as well as a summary of the factors that affect the amount of
water that cows, heifers, and calves can be expected to drink.
2
Another excellent reference on water and

a

Stray voltage is defined by the Public Service Commission of Wisconsin (PSCW) as a natural phenomenon that can
be found at low levels between two contact points in any animal confinement area where electricity is grounded.
Electrical systems - including farm systems and utility distribution systems- must be grounded to the earth by code to
ensure continuous safety and reliability. Inevitably, some current flows through the earth at each point where the
electrical system is grounded and a small voltage develops. This voltage is called neutral-to-earth voltage (NEV).
When a portion of this NEV is measured between two objects that may be simultaneously contacted by an animal, it is
frequently called stray voltage. It is the level of concern defined as follows that dictates the significance of the
voltage at cow contact. In Wisconsin, the level of concern is derived from the 1996 PSCW docket 05-EI-115. In that
docket, the level of concern is defined as 2 milliamps, AC, rms (root mean square), steady-state or 1 volt, AC, rms,
steady-state across a 500-ohm resistor in the cow contact area. The Institute of Electrical and Electronics Engineers
(IEEE) defines steady-state as the value of a current or voltage after all transients have decayed to a negligible
value. The State of Wisconsin deems that this level of voltage/current is an amount of electricity where some form of
mitigative action is taken on the farmers behalf, although only some small percentage of cows may actually perceive
its presence. The level of concern is not a damage level. Instead, it is a very conservative, pre-injury level, below
the point where moderate avoidance behavior is likely to occur and well below where a cows behavior or milk
production would be harmed. The level of concern is further broken down into two parts. The first part is a
1-milliamp contribution from the utility, at which level mitigative action must be taken by that utility to reduce its
contribution to below the 1-milliamp level. The second part is a 1-milliamp contribution from the farm system, at
which level mitigative action should be taken by the farmer.
the use of a water intake prediction formula is the chapter on water in Large Dairy Herd Management.
3

Personal experience has shown that these equations are rarely used to assist farmers concerned about water
intake. Without exception, on REPS farm investigations between 1994 and 2002 where water consumption
was a concern, none of the local farm service professionals (i.e. veterinarians, nutritionists, milk plant field
persons, or university extension professionals), who were actively advising the farmers, exhibited
familiarity with the available formulas that predict water intake.
In these herds, if any guidelines on water intake were provided, they were based on a loose
application of simplistic rules of thumb. Typical of these are: a cow should, drink more than 30 gallons
of water a day,
4
or about 29 gallons of water a day.
5
Compare the rule of thumb printed in a popular
dairy magazine article and the estimates based on the NRC recommended formula. The rule of thumb is a
cow should drink a half-gallon of water, including water from feed, for each pound of milk produced.
4

For a cow producing 80 pounds of milk this should predict her total water needs at 40 gallons. If, however,
the ration is 50% water, and dry matter intake is 50 pounds then the ration should provide around 6 gallons
of water. Even if this source of water were factored in the predicted intake would only be reduced to 34
gallons. The Murphy-1983 formula recommended in NRC predicts, for an average winter barn temperature
of 40
o
F, that the cow should be expected to need only 25 gallons of water. Not until the average minimum
temperature of the week rose to 90
o
F, or the dry matter of the ration was over 90% should water
consumption predicted by the NRC formula begin to approximate the amount predicted by the rule of
thumb.
Articles written in popular dairy magazines commonly discuss the importance of improving water
intake, especially in relation to reducing the negative impact of heat stress.
6
The importance of water as a
vital nutrient and assuring adequate access to water are well understood.
7, 8
What is not well understood is
whether or not increasing water intake in itself is a worthwhile goal. If a cow consumes the amount of
water that standard intake formulas predict, will additional water intake improve milk production, or will
the surplus merely be lost in increased urine output and fecal moisture? It is common for dairy farmers to
profitably use a variety of methods to coax their cows to eat more feed. Is it beneficial or even possible to
coax a cow to regularly drink more water than she needs?
Veterinary and dairy scientists generally believe that if cows could be enticed to consume surplus
water, the surplus water would be excreted as urine and manure without a beneficial effect on milk
production. Two studies in goats found that after hyperhydration (10% of body weight) 46% of the load
was excreted by the kidneys within 6 hours, and that there was no storage of excess water.
9, 10
Water
intoxication, a type of timing-related hyperhydration that occurs with sudden rehydration after extreme
dehydration, can cause serious leakage of hemoglobin into their urine and neurological problems.
11

Although one author suggests, adequate intake from a quality water source will improve dry matter intake
and overall milk production,
12
no studies have actually documented whether or not increasing water intake
slightly above a dairy cows required needs is of any health or production benefit.

The importance of the above discussion is that reduced water intake is interpreted as a sign of
stray voltage on 50% of farms visited by the REPS program.
1
However, experience on farm visits where
these concerns exist have shown that:

1) Farmers have not been advised of the existence or use of industry standard formulas to predict
actual water intake.
2) Advice given to farmers about depressed water intake is based on overly simplistic rules of
thumb.
3) There has not been adequate effort to determine whether or not water consumption is meeting
water needs.
4) There is the dubious expectation that if water consumption can be increased it will be
beneficial to herd health or production.

Local farm professionals, who rarely need to work with water issues, are not the only source of
poor information about water. Field experience has provided plenty of examples where representatives of
large dairy feed companies suggested to farmers that herd water intake was reduced due to stray voltage
without verifying any reduction. When farm service professionals make the unverified suggestion that
stray voltage is causing a herds water intake to be depressed, and stray voltage mitigation efforts
(coincidentally) fail to produce an increase in water consumption, the real problem is that the farmer is put into a highly vulnerable position. For some, the improvement of a fictitious water intake problem can be a
very expensive business mistake.



Reduced water intake

The effects of reduced water intake on dairy cows has been studied. Well documented in
veterinary literature is the acute event of water intoxica