Electric Fencing

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The portability of temporary electric fencing means it can he moved about according to pre-planned grazing patterns. The practice allows more intensive use of pasturelands than is possible with permanent fencing of larger areas. Aaron Silverman raises about 15,000 broilers a year in a small valley in Oregon. "Our fields are bordered by riparian zones — a river or a creek where there are nesting marsh hawks and red-tailed hawks, bobcat runs and coyote trails.

"When we started with traditional pastured poultry zones, we confined the birds to the portable enclosures at all times and moved the enclosures once, maybe twice a day. We noticed that whenever we were close to a riparian zone, we would lose birds to raccoons, 'possums and skunks, which were able to sneak under the fencing."

To establish secure outdoor pens for the birds, Silverman tested electric sheep netting, with mesh small enough to stop coyotes, but not weasels, "so we were still losing birds." Next, he tried electric poultry netting with 2-by-3-inch openings and thin, rigid-plastic verticals that keep the fence upright without corner tension braces.

"That pretty much took care of it," he says. The netted fence keeps out predators as small as rats — as long as it's moved regularly. When left in place for several weeks, such as around a greenhouse-turned-brooder house, rats eventually tunnel underneath to get at the chickens. "In the field," he says, "where we are moving the fence on a continual basis, they (the rats) respect it."

HOW IT WORKS

Electric fencing runs on a charger, which converts a typical 110-volt, 15-amp branch circuit, such as those you might find in a house, into a pulsed, high-voltage, low-current output. Although the potential involved may be on the order of 2,500 to 9,000 volts, the current is limited to a safe level and the actual pulse lasts only milliseconds.

According to David Hart of Underwriters Laboratories, a minimal one-second duration is mandatory between pulses to allow people who inadvertently grab onto a "hot" wire the time to let go and avoid injury. Continuous current causes the muscles to contract, making letting go difficult and potentially interfering with the function of the heart.

The fence wire is connected to a ground rod, usually just a galvanized pipe that has been driven deep into the ground. Any conductive material, such as a critter's nose or ears, that touches the wire after it has been electrified completes the circuit and — ZAP! The critter gets a short but unpleasant shock.

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