Good fencing protects and confines valuable livestock by presenting barriers to restrict animal movement. Barriers may be physical, psychological or a combination of both. Fencing type and material influence the cost, lifespan and function of the fencing system.
Woven Wire Fences
Woven wire fences consist of smooth horizontal (line) wires held apart by vertical (stay) wires. Spacing between line wires may vary from 1 1/2 inches at the bottom for small animals to 9 inches at the top for large animals. Wire spacing generally increases with fence height.
Woven wire fences are available in numerous combinations of wire sizes and spacings, number of line wires and heights. Most fences range in height from 26 to 48 inches. Stay wires should be spaced 6 inches apart for small animals and 12 inches apart for large animals.
The standard design numbers listed on the manufacturer's tag (attached to fence rolls) describe the fence. For example, a design number of "1047-12-11" indicates that the fence has ten line wires and is 47 inches high, has 12 inches of spacing between stay wires, and has 11-gauge filler wires (wires between the top and bottom line wires).
Barbed Wire Fences
Barbed wire consists of two or more strands of smooth, galvanized wire twisted together with two or four sharp barbs spaced every 4 to 5 inches. Standard barbed wire fences usually have three to five strands of barbed wire stretched between posts. Typical fence height is either 51 or 54 inches. Spacing between wires depends on the number of line wires and fence height. Line posts are usually spaced 12 to 20 feet apart.
Suspension barbed wire fences consist of four to six strands of 12 1/2-gauge barbed wire stretched taut so no more than 3 inches of sag exists between posts. The wire strands are held apart by twisted wire stays or plastic battens or droppers spaced 16 feet apart. Line posts are usually spaced 80 to 120 feet apart.
Cable Wire Fences
Cable wire fences are expensive and generally used for confinement areas. These fences consist of 3/8-inch steel wire cables stretched between anchor posts. Fence height varies from 60 inches for a 4-cable fence to 72 inches for a 6-cable fence.
A heavy-duty spring is fixed to one end of each cable and attached to an anchor post to absorb the shock on the wires caused by animal contact. The fence may consist of as many cables as desired, although a 6-cable fence is recommended for large animals.
Mesh Wire Fences
Mesh wire is made in 11, 12 1/2, 14, and 16 gauges and fences are available in diamond-mesh and square knot designs. Fence height generally varies from 50 to 72 inches. The square knot wire design is formed from single line wires spaced 4 inches apart and stay wires spaced 2 inches apart. The joints are held by a piece of short wire formed into a knot.
The diamond-mesh wire design uses two smooth wires spaced 4 inches apart and twisted together for all line wires. Stay wires consist of single smooth wires the same size as the line wires. These are wrapped around adjacent line wires to form a triangle with a 2-inch base. The diamond shape is formed when two of these triangle bases are fitted together.
Both mesh fence designs are strong and highly safe for animals. However, these fences are expensive and used primarily for confinement areas or small acreages.
High Tensile Fences
High tensile fencing is easy to handle, requires little maintenance and can be relatively low-cost. This type of fencing can withstand livestock contact and low temperature contraction without losing its elasticity. High tensile wire undergoes reduced stretch or sag, which is commonly associated with conventional fence wire. This type of fencing is not recommended for horses unless electrified versions are used and the owner is willing to accept some risk of injury.
High tensile fencing is constructed with 11- to 14-gauge wire with a tensile strength of 170,000 to 200,000 pounds per square inch (psi) and breaking strengths of approximately 1,800 pounds. Wires are held in tension along posts spaced 16 to 90 feet apart. At installation, each wire is tightened with a permanent in-line strainer and is set at 200 to 250 pounds of tension. In-line strainers should be placed near the middle of the fence line to provide the same tension in both directions.
Tension indicator springs are used to set and maintain the correct wire tension. Use one tension spring on one wire per fence and set it to the proper tension. The other wires can be tightened to the same tension by feel or sound (similar to tuning a guitar). The tension spring is generally set on the second wire. However, placing the tension spring on the top wire provides some additional "give" to minimize damage caused by falling tree limbs.
Temporary electric fences can be constructed from numerous products. One of the more popular products consists of fine aluminum or stainless steel wires woven together with polyethylene fibers to form what is known as poly tape. This product comes in various colors with black being the most difficult for animals and humans to see. Brighter colors such as white or orange are much easier to notice and are recommended where visibility is especially important. Poly tape is also available in various wire densities. The maximum length for poly tape with a low wire density is about 1200 feet. Poly tape with a high wire density can be used for longer runs.
Permanent electric fences generally consist of two or more strands of smooth wire. However, fences designed for small predator control may have as many as ten or 12 strands. Alternate wires are hot. Other wires serve as grounded returns to the controller. The ground wire return design is recommended where the soil may be dry some of the time.
Permanent electric fences can be built from aluminum, stainless steel and high tensile wire. These types of wire conduct electrical charges for longer distances than poly tape. However, they are more difficult for animals to see. Animals will not be effectively trained to avoid electric wire unless they can see the wire as they feel the shock. Attaching strips of brightly colored cloth or plastic to the wire creates contrast and movement for easier visibility.
This was published originally as "Fencing Materials for Livestock Systems," by Susan Wood Gay and Rick D. Heidel, Virginia Tech, Publication Number 442-131, Revised 2003.