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Symptoms of Stray Voltage

Some of the changes in animal behavior are:

  1. Cows are excessively nervous during milking (dancing around in the stall)
  2. Cows are reluctant to enter the parlor or stall
  3. Cows are reluctant to use waterers or to consume feed
  4. Poor milk letdown

Causes of Stray Voltage
Sources of Stray Voltage can be from off-farm and on-farm sources. Off-farm sources of Stray Voltage can be related to primary neutral-to-earth voltages, and can be dealt with by MVEC. Common on-farm sources of Stray Voltage on dairy farms are: worn insulation on wiring, loose wiring connections, improper use of equipment grounds, electrical shorts, unbalanced 120 volt loads, and improper installation of electric fences or cow trainers. All of these sources of Stray Voltage can be corrected.

The special requirements for wiring of livestock buildings are explained in detail in the Farm Buildings Wiring Handbook. Detailed information on Stray Voltage and how correction of farm wiring can help solve Stray Voltage problems are also given in this handbook. The handbook can be obtained by writing to the following address:

University of Minnesota
Department of Agricultural Engineering
Attention: Ms. Wendy Yates
1390 Eckles Avenue
St. Paul, MN 55108

Share this information with any licensed electrician who installs new equipment on your farm or alters any wiring. Be sure to specify that you want all work to be done in accordance with article 547 of the National Electric Code. In addition, be sure that all electrical work is properly inspected as required by state law.

Improper grounding is a safety problem
Proper use of grounding wires on electrical equipment is required in all buildings. However, this is a common oversight on many farms. Improper grounding is not only a cause of Stray Voltage, but it is also a safety hazard. If you suspect that you have a grounding problem, have a licensed electrician inspect the wiring on your farm to determine if it meets all requirements for livestock buildings. Use the Farm Buildings Wiring Handbook (MWPS-28) as a guide. Make all necessary wiring corrections.

What to do if a Stray Voltage or safety problem is suspected
Do not delay. If a Stray Voltage problem is suspected, begin the problem-solving process by taking all of the following actions. Contact MVEC and explain your concerns. MVEC can provide a complete Stray Voltage investigation. Obtain copies of the following educational materials from the sources previously indicated: Stray Voltage Problems with Dairy Cows (AG-BU-1359) (; and Farm Buildings Wiring Handbook (MWPS-28) (1-800-562-3618). Have a licensed electrician inspect the wiring on your farm.

Preventing Stray Voltage
Make sure that all new livestock buildings and milking centers are wired according to the special requirements given in the National Electric Code (Article 547). Have the wiring properly inspected. In new milking parlors, installation of an equipotential plane is highly recommended.

For more information contact:
Jeff Langeberg, Technical Service Supervisor
(952) 492-2313 or (800) 282-6832


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