Hooked on Stray Voltage

Posted: November 2, 2005

Stray voltage allows everyone to blame a variety of common dairy herd production problems on something out of their control and to discount other obvious changes or improvements under their control that could help cow productivity and thus farm profitability.

“It lets them get off the hook!” These words were used by a medical expert to explain why people ignore professional medical advice and then buy an unproven cure from an infomercial or classified add. It allows them to not have to admit what might really be wrong and that there are things under their control that they could do to improve the situation; it allows blame sifting. This reminds me of experiences I have had with stray voltage on dairy farms. A variety of scientific studies have demonstrated that cows will have an undesirable behavioral response to AC currents of 4 mA (milliamps) or higher flowing through their bodies. However, some farmers will insist that their problems are stray voltage even after appropriate surveillance procedures detect no significant levels of voltage or current at cow contact points. Stray voltage provides the opportunity to blame low production, high SCC and a variety of other maladies on a cause that they can claim is out of their control. Often farm advisors and venders will willingly promote this belief since it takes the spotlight off their areas of involvement. Stray voltage allows everyone to blame a variety of common dairy herd production problems on something out of their control and to discount other obvious changes or improvements under their control that could help cow productivity and thus farm profitability.

What is even more discouraging is that they dismiss qualified experts when they point out other issues that are affecting cow productivity and farm profitability. This hook allows for convenient blame shifting for almost everyone. Stray voltage can’t be seen, can’t be felt and for most is not understood. The farmer, the milker, the nutritionist or veterinarian, the list is endless, can all line up and point the finger at something that is out of their control.

The stray voltage hook can also be productive for folks who are selling cures. Everyone is vulnerable to the promise of a quick and easy fix. These cures go from the ridiculous to the sophisticated and can often result in large expenditures of money and diverting resources (time and money) from other activities would help productivity.

The end result is the stray voltage hook holds the farm back from investigating and improving practices that have a high probability of increasing productivity. It provides a convenient and effective fishing hook for those trying to sell an easy cure. It provides a non-farm or advisor controlled hook to blame a variety of productivity problems on. “I could do better if only I didn’t have this mysterious problem.” Anyone who reinforces and supports this theory is listened to. Someone who comes along and points out other possible farm controlled deficiencies is ignored.

Field experience indicates that up to 90% of all suspected stray voltage problems are something else. With those odds, farmers who wish to be profitable may need to be careful of the stray voltage hook and start looking at other logical and controllable influences on cow productivity.

The take home message is that cows will react adversely to AC current flow of more than 4 mA; measured as 2 volts AC with a 500 ohm resistor in the circuit to simulate the electrical resistance of the cow. There are well documented surveillance procedures to determine if areas where cows walk, drink, eat or stand to be milked allow them to complete an electrical circuit that exposes them to stray voltage levels of concern. If you and your health and management advisors have good reason to suspect stray voltage the following steps should be taken.

  1. Arrange to do a stray voltage screening test. Your power supplier, electrician or milking machine service technician can often help with this process. A simple hand held meter can provide instantaneous readings and help you identify continuous levels of concern at cow contact points. If none are found it may be desirable to arrange for a 3-4 day recording of a suspected cow contact point. If level of neutral to earth voltage above 2 volts AC are discovered on the farm secondary neutral the power company will need to be involved to help determine if the source is on the farm or the primary distribution system. Because this will involve operations on the power company’s system and working around high voltage electricity the power company must be involved to safely and properly make these determinations.
  2. Have a qualified electrical inspector, electrician or other technician investigate the farm wiring and electrical distribution system for code compliance and general condition paying particular attention to grounding and bonding, connections and terminations between the transformer and barn circuit panel, balanced 110 volt loads, branch circuits and sub panels.
  3. Evaluate the milking system and procedure preferably including measurements and observations during actual milking.
  4. Review feeding, housing, health, breeding and other important cow management systems and procedures.

Always be on guard that you are not getting hooked on stray
voltage or hooked by people taking advantage of stray voltage
and as a result missing obvious problems and their fixes.

Robert E. Graves, Agricultural Biological Engineering Extension