Agricultural fencing

[1][2] Historically throughout most of the world, domesticated livestock would roam freely and were fenced out of areas, such as gardens or fields of crops, where they were unwanted.

Though the open range was part of the western tradition, over time, open range was limited long before it was eliminated; first came an obligation to keep cattle from roaming onto state and federal highways, where collisions with fast-moving cars and trucks created a public safety hazard.

Over time, court cases steadily limited the application of open range law until the present day, where it is the exception rather than the rule in many parts of the American West.

Additionally, railways in the UK are fenced to keep livestock and people out, since it is a requirement to do so, unlike many other countries.

To prevent sagging of the fence, which raises the risk of entanglement or escape, the wire is tensioned as much as the material will safely allow during construction by various means, including a hand-operated "wire stretcher" or "fence stretcher"[4] (called a "monkey strainer" in some areas) or other leverage devices, a winch, or even by carefully pulling with a tractor or other vehicle.

Wire fences are typically run on wooden posts, either from trees commercially grown in plantations or (particularly in the American West) cut from public lands.

Creosote, pentachlorophenol, and chromated copper arsenate are all widely used in the US and elsewhere for treatment (although some of these chemicals are subject to legal controls).

In the United States, introduction of barbed wire contributed to the range wars of that century, as various ranch interests attempted to use barbed wire fences to claim exclusive access to the best pasture and water resources, including those lands in the public domain.

It also exacerbated tensions between cattle ranchers and crop farmers, partly when access to water was involved.

However, animals will readily lean on mild steel smooth wire, stretching it out of shape or loosening it from the posts, and for this reason it is often used in high-tensile form, which more easily springs back to its original length.

HT wire is more expensive than mild steel, but because of the need for fewer posts, the overall cost of the fencing is usually comparable.

Trellising for horticultural purposes is generally constructed from HT wire as it is able to withstand a higher crop load without breaking or stretching.

Barbed wire fences cannot effectively contain smaller livestock such as pigs, goats or sheep.

Large hoofed animals can put a foot through wide squares while grazing along the edge of the fenceline or while reaching over it, and then become tangled in the fence.

However, due to cost, it is not particularly common for fencing large areas where less-expensive forms of woven wire are equally suitable.

When used in small enclosures, it is easily deformed by livestock, resulting in high ongoing maintenance costs.

Synthetic web or rope with thin steel wires interwoven to carry the electrical charge has become popular in recent years, particularly where additional visibility is desired.

Some forms are non-electric, others embed layers of graphite to carry a current from the wire to the outside of the coated product so that it can be electrified.

For example, scrap pipe is often easily obtained at a low price if oil fields are nearby, and wooden rails can sometimes be harvested from the owner's own land if it contains suitable standing timber.

A cattle grid is an obstacle used to prevent livestock, such as sheep, beeves, pigs, horses, or mules from passing along a road or railway which penetrates the fencing surrounding an enclosed piece of land or border.

Cattle and horses are strong enough to go through most types of fence by main force, and occasionally do so when frightened or motivated by hunger, thirst, or sex drive.

Woven wire can barricade animals that cannot jump the fence but are too large to crawl through the holes, such as fawns, bears and bobcats.

Reducing the height of woven and strand wire fences to no more than 40 inches can make it easier for wildlife to jump over with less risk of entanglement.

Using barbless wires on top and bottom reduces cuts on wildlife which crawl under strand fences or those that try to climb over.

[12] Fladry lines, made of cloth, metal and/or other materials, are sometimes used on fences to discourage wolves from entering a livestock enclosure.