For many rotational grazing practitioners, the electric fence is a critical component of the system. The grazier trusts in the electrical system and the prior experience/training livestock have received to ensure the fence is not crossed. But in dry years, says Rory Lewandowski, Ohio State University Extension educator, marginal electrical fence systems may not maintain the desired voltage. Dry soils don't provide the same grounding between animal and fence, as wetter soils do. And fences that might not be challenged in a year with plentiful forage may be tested in dry years with limited forage growth.
Because paddock rotations tend to slow in times of lower forage production, or animals are detained in a "sacrifice area" until grass growth allows the rotation to be resumed, can your fence keep your livestock from moving to where the grass really is greener? In that vein of thought, perhaps it is beneficial to review the basics of electric fencing. Citing "Beef Cattle Handbook, BCH-6201: Fence Systems for Grazing Management" and the Kencove Farm Fence Supplies Catalog, Lewandowski offers these fencing thoughts.
The basic components of an electric fence system include the fence energizer/charger, ground rods and the fence wire. The energizer/charger is the "heart" of the electric fence system, and a beginning grazier can avoid a lot of frustration by spending the necessary money for a high-quality energizer/charger. An energizer/charger isn't the place to cut budget corners.
- Size the energizer/charger to handle your current fencing system, plus factoring some room for growth. As the amount of your fencing grows -- either due to increased grazing area or addition of more paddocks -- graziers should check to ensure their energizer is adequate for the amount of fence they're asking it to charge.
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- Check the voltage on the fence to ensure it's adequate to deter livestock from crossing. Some ballpark figures include: 1,600-2000 volts for cattle, 3,000 volts minimum on electric netting for sheep and goats, and 4000+ volts on high-tensile fence for sheep/goats.
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- Evaluate the charger/energizer as your fencing needs change. The answer may be another charger/energizer in the system, or opting for a larger unit to handle the increased load. To evaluate chargers/ energizers, look at its output in joules. Remember that when a product boasts the miles of fence it can energize, it's referring to one wire. If multiple wires are energized, these must be added together to arrive at the system's true capabilities. For instance, four strands of high-tensile wire around a mile perimeter with two hot strands accounts for two miles of energized wire.
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- A sometimes-overlooked component of the electric fence system is the ground rods. A charger/energizer's full capacity won't be utilized unless a good ground system is in place. In a dry year, it's critical to install the correct number of ground rods -- properly spaced -- to help keep enough voltage on fences. A general rule of thumb is a minimum of 3 ft. of ground rod per joule of energizer output capacity.
For instance, a 15-joule energizer requires 45 ft. of ground rods. Either galvanized or copper rods in 6- to 8-ft. lengths are used. Thus, this energizer would require 6-8 ground rods depending upon if 6- or 8-ft. ground rods are used.
If using copper rods, use a copper wire from the energizer ground terminal to the ground rod. If different metals are mixed, electrolysis can occur and the effectiveness of the grounding system is reduced, so stick with either galvanized or copper.
Ground rods should be driven in their full length. If rocky soils don't permit this, drive it in at an angle so the rods essentially are lying in a trench. Ground rods should be at least 10 ft. apart and 40-50 ft. away from any other existing grounds. Ground rods should be tied together in a system, connected with wire between rods.
Try to locate ground rods in an area likely to stay moist. Northern exposures under building drip lines often work well. In drought situations, it may be a good idea to water your ground rod areas to increase the fence's effectiveness. -
- Finally, evaluate the fence itself. Remember that as the diameter of the fence wire decreases, there's more resistance to push electric current around the fence.
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- Polywire is very handy stuff but it shouldn't be used to carry the charge long distances. Use high-tensile wire to carry the charge -- and for perimeter fencing -- and polywire to hook on to the high-tensile wire for internal paddock divisions. Also be aware that if barbed wire is used in an electric fence system, each of those barbs siphons off electricity, thus reducing efficiency.
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- Voltage drops in the fence as distance and amount of fence increases. Check to make sure the galvanized coating on the fence wire is intact. Rust is an enemy of electric fences.
