Kōrero: Farm fencing

Whārangi 5. High-tensile and electric fencing

Ngā whakaahua

High-tensile wire

In the 1960s a new type of wire was introduced. High-tensile 12½ gauge (2.5-millimetre) wire offered an economic benefit over the iconic No. 8 wire. Although it is less pliable and more difficult to cut and tie, you get more length of 2.5-millimetre gauge per tonne, and it is therefore much cheaper. In the 2000s, farmers use about five times as much 2.5-millimetre gauge fencing wire as they do No. 8.

Olympic fencing

A fencing competition has been held every year at the National Fieldays, New Zealand’s largest agricultural event, since it began in 1969. The competition attracts the cream of the country’s fencing contractors. In the singles final, competitors have to erect a 50-metre post-and-wire fence strung with nine 2.5-millimetre wires. A similar fence is built in the doubles competition, except that more posts are required and the two top wires are electrified.

Tanalised timber

Until the 1950s, wooden posts and battens for fencing were cut from native timber. Tōtara was the most popular as it lasted well in the ground. Exotic pine, although cheap and plentiful, was not used as it rotted when in contact with the soil. This changed with the advent of tanalising. Radiata pine treated with chromated copper arsenate (CCA) is much more resistant to rotting and makes cheap posts, battens and timber for fencing. Most farm fences built in New Zealand since the 1960s have been made of tanalised pine posts and 2.5- millimetre gauge high-tensile wire.

Electric fencing

Perhaps the most revolutionary advance in fencing since steel wire in the 1860s has been the electric fence. This exploits the learned response of stock to a short, sharp electric shock when they come in contact with the wire.

It was not a New Zealand invention, but local farmers and inventors have been leaders in its development. Bill Gallagher and Herbert Christie, working separately, designed and built electric fence energisers in New Zealand about 1938. At the same time, William Riddet was also working on the concept at Massey Agricultural College (now Massey University).

At first, electric fencing was used to support existing wire fences and as temporary fencing for cattle. In 1958, trials on permanent electrified fencing were conducted at Massey, and introduced a radical change in fencing methods.

Advantages and disadvantages

Since they do not need to provide a heavy physical barrier, electric fences can be built much more cheaply than traditional fences. They need fewer posts and wires, and require less labour to put up. Although the system works on high voltage, it also has a low amperage, and the way the current pulses makes it safe for humans, even though they can receive a shock.

However, there are disadvantages. Since electric fences rely on a high-voltage current, any loss in power reduces their ability to control stock. Attention to detail is vital for the system to work properly. The fences also need to be checked regularly to pre-empt any faults. When faults do occur they are often difficult to find. So there is a much higher labour input to maintain electric fences than traditional fences.

Electric fencing and intensive grazing

Electric fencing has transformed intensive livestock farming. Break-feeding of fodder crops for wintering and fattening stock has been practised in New Zealand since the 1870s. In this system a paddock of saved feed is divided into breaks so that stock have access to only part of the crop at any one time; this reduces trampling and wastage.

Before the days of electric fencing, breaks were made with netting and wooden stakes, and it was a laborious job to erect and dismantle them. Lightweight electric fencing materials have made the task much less labour intensive. Livestock farmers can now use their saved feed and fodder crops more efficiently, and thereby better manage the nutrition of their animals.

Powering electric fences

Permanent electric fences are usually powered by the mains power that runs the homestead and farm buildings. Often the main feed line to the fence is run from the farm workshop or woolshed. Permanent electric fences on remote parts of the farm often use a solar panel that charges a battery.

Temporary and portable electric fences used for break feeding can be powered from the mains supply. Often they are run by solar-charged batteries.

Deer fencing

Deer farming in New Zealand would not have been possible without the development of purpose-built fences. Deer are flighty animals that can comfortably leap traditional fences, or push between wires that are tightly strained. A New Zealand company, Cyclone, made the world’s first deer netting fence in 1967. Deer fences are required to be 1.9 metres high and are normally constructed of tanalised pine posts and netting designed specifically for holding deer.

Me pēnei te tohu i te whārangi:

Robert Peden, 'Farm fencing - High-tensile and electric fencing', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/farm-fencing/page-5 (accessed 12 December 2018)

Story by Robert Peden, published 24 Nov 2008