Many of the causes of stray voltage on-farm can be figured out and solved, says Dr. Paul Dettloff of Arcadia, Wisconsin. He says 75 percent of the time, on-farm solutions can be found rather than pursuing lengthy and costly lawsuits. He has observed and studied stray voltage (DC current) over the past five decades.

Freelance Writer
Boylen is a freelance writer based in northeast Iowa.

Dettloff says what many people refer to as stray voltage is actually grounded current taking the path of least resistance.

“Our electrical distribution system utilizes the ground as the return to bring grounded electricity back to the substation,” he says. “All poles and transformers and service entrances are grounded. Fencers and waterers are also grounded. When AC current is grounded, it becomes DC current, and this returns to the substation.”

All buildings with animals in the U.S. by law have to be an equi-potential plane, Dettloff says.

“This means anything that can conduct electricity in a new or remodeled building has to be all bonded together, including the re-rod in concrete, the metal stalls, the water pipes and metal buildings themselves.”


So the bigger the building (equi-potential plane), the lower the ohm resistance.

“Electricity takes the path of least resistance,” he explains. “A facility having a lower resistance than the power grid creates a problem. For example, if a farmer grounds his fencer by the milking facility, the DC current from the fencer will seek out the lower-ohm building instead of the poles to the substation.”

Electromagnetic fields from cell towers, radio towers and the larger electrical power lines will induce DC current when it comes in contact with anything that conducts electricity, he adds. Ground currents in the soil will vary with the moisture and organic matter, and they do not always follow the power lines and poles.

“Sometimes the cause of the DC current problem is in plain sight. If transformers are corroded or rusted, they are usually overloaded,” Dettloff says. Contact your power company. It is possible they are not even aware the transformer is not in top condition.

It is best to have transformers as far away as possible from where cattle are housed and milked; transformers should be at least 200 feet from barns and homes. The distance from a transformer, the wetness of the soil and soil type can all influence DC current issues.

If metal barn roofs or silo roofs have sections that are rusted or corroded without other known causes, that is also a red flag. Dettloff has seen where a silo unloader is sending current through the metal barn to the grounded service entrance on the other side of the barn, right through the milking parlor.

The new variable-speed motors that are replacing the single-phase motors have a large electromagnetic field.

Some suggestions Dettloff has for dairy producers include:

  • Avoid metal waterers; use poly or rubber waterers.

  • Plate coolers and metal pipelines should have dielectric couplers to break current flow.

  • Fluorescent lights have electromagnetic fields; use LED lights whenever possible.

  • Never ground a fencer in a cow yard or barn.

  • Use wooden or fiberglass posts instead of metal posts for electric fences.

Graziers also need to be aware of how electric fences can affect water lines. He recommends keeping water pipes at least 6 feet from electric fences and never run electric fencing over a water tank unless it is 10 feet above the waterer.

“Consider using solar fences and ground them on the back forty,” he says. Fencers should not be located in any cattle facility.  end mark

Kelli Boylen is a freelance writer based in Waterville, Iowa.

Dr. Paul Dettloff is an industry consultant on sustainable agriculture, is a staff veternarian for Organic Valley Coop in Wisconsin and owner of Dr. Paul’s Lab, LLC.


Behavior common in dairy cows being affected by stray voltage include:

  • Bulging eyes

  • Cows pressing their heads or noses to metal and lifting legs

  • Thirsty cows not drinking/ dehydration

  • “Dancing” in their stalls

  • Tail twitching

  • Kicking milkers off

  • Lapping water with tongues

  • A softball or larger enlargement at the bottom of the neck in brisket area

  • High somatic cell count

  • Low immune function