March 21, 2015

How to design an electric fence that works for your farm.

Shock Therapy: The Right Electric Fence for Your Farm

By Ann Larkin Hansen | Illustration by Ray E. Watkins Jr.

Modern electric fencing is perhaps the most versatile and cost-effective tool available for containing domestic animals or protecting plantings, poultry and livestock. It also has revolutionized sustainable agriculture by making rotational grazing (aka management-intensive grazing) easy and flexible. But an electric fence works only if all the pieces are connected right and the type, number and height of wires are suited to the critters you want to keep in or out.

Types of Wires
Wires for electric fences are either metal or plastic. Metal wire is best for permanent structures, while the light, flexible plastic wires (called polywire) are perfect for temporary fences. Use thicker polyrope or polyribbon for more visible enclosures. For small areas and poultry, you can’t beat electric net fencing. But the larger the area, the less practical it becomes since it’s expensive as well as awkward to set up and move. To use wires instead of net, start with our recommendations for heights and spacing for various animals (thanks to electric fence-supply companies Premier and Gallagher for their assistance). If your fence doesn’t adequately control the animals you’re trying to keep in or out (see below), and you’re sure you have enough voltage and a good ground system, then add wires, move them closer together or put a grounded wire between the charged wires. Often we’re trying to control more than one type of animal with the same fence, such as sheep and coyotes. Always build and charge the fence for the more difficult-to-control animal, and don’t hesitate to use additional wires—either higher, lower or more closely spaced—to ensure good control. For most domestic animals, you’ll want a minimum of 2,000 volts on the fence wire. For sheep and wild animals, have a minimum of 4,000 volts. You won’t need more than 8,000 volts for any type of animal.

Keeping Animals In
Poultry. Use electric net or several wires set just a few inches apart so as to both keep the birds in and predators out. Sheep and goats. Start with three wires at 10, 20 and 30 inches high. Add more wires more closely spaced, if needed. Pigs. Use polyribbon or rope, and start with wires at 8 and 16 inches high. Pigs are very sensitive to electricity, but have poor eyesight. Equines. Since horses, mules and donkeys come in all different sizes, place three wires at the average height of your herd’s knees, point of shoulder and at or a little below the withers. Horses tend to outrun their eyes, so using highly visible polyribbon, rope or fluttering strips of plastic on at least the top wire is a good idea. Cattle. The easiest of domestic animals to contain with an electric fence. For pasture subdivisions, a single strand of polywire at nose height is usually all that’s needed. For more permanent fences, use three strands of electric wire or offset insulators to run a single electric wire along a permanent physical fence.

Keeping Wild Animals Out
Rabbits. One wire 3 or 4 inches off the ground. Raccoons. Two wires at 6 and 12 inches high. Woodchucks, small dogs, cats. Three wires at 4, 11 and 18 inches high. Larger dogs, coyotes and wolves. Lowest wire at 6 inches above the ground; other wires spaced 6 to 7 inches apart, up to a height of at least 42 inches. Bears. Three wires spaced 10 inches apart, starting at 10 inches above the ground. Since bears have such poor eyesight, use polyrope or polyribbon instead of metal wire or polywire, or tie fluttering plastic or tinfoil strips to the wire. Deer. Build a three-dimensional fence. First, build an outer fence using a single wire 30 to 32 inches high, and an inner fence 3 feet away, with two wires at about 20 and 48 inches in height. Deer are great jumpers but have poor depth perception, and this fence confuses them enough to stop them from jumping.

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