January 15, 2009

Cattle farm husbandry - fencing for cattle

Cattle, farming, husbandry, fencing, the law, methods, power fencing, recommendations, advice, wire spacings, trouble shooting.

By Dr Clive Dalton

Are your stock secure?
Making sure your stock stay where you put them is extremely important for many reasons. A major one is your legal responsibilities if they escape causing damage to property, and worse still cause an accident on the public highway. So having good fences is crucial.

Fence types

NZ Standard boundary fence

A legal New Zealand standard boundary fence that will be
free of maintenance for at least ten years.
  • This is the basic legal boundary fence required under the law (The Fencing Act 1978) in New Zealand.
  • It is the best stock-proof fence there is, but it’s the most expensive.
  • It has got to be a seven-wire, fully-battened fence, and is the perfect stock-proof fence if well erected.
  • It usually has posts 5 m apart with 5 battens equally spaced between them.
  • The gaps between the seven wires from ground level to top are at intervals of 120mm, 120mm, 130mm, 150mm, 170mm, 200mm and 250mm.
  • Some people still put a barbed wire on the top for cattle but this should be avoided. They argue that it's easier to keep the battens in place. Proper stapling will fix this problem.
  • For more stock security electrified wires can be added (see below).
There is no need for barbed wire on fences any more. It damages hides and
injures stock and people. It should be banned from farms.

Electric or power fencing

This is a very cost-effective solution to restraining cattle and New Zealand has led the world in its development. It can be used as a stand-alone power fence, or be added on to a standard fence. If your standard fence is in bad repair and cash is short, adding a hot wire to it is a good way to get a few more years out of it.

There's a wide range of power fencing energizers on the market.
Some will power over 200 km of fence.

Advantages of power fencing
  • Low cost.
  • Easy to construct with light materials. It’s much easier to get power fencing materials out to the back of a farm than with standard fencing.
  • It lasts a long time as there’s minimal stock pressure on it.
  • It’s easy to use for subdivision of paddocks improving grazing control.
  • It’s easy to modify to suit the stock and if you find it’s in the wrong place, it’s easy to shift.
  • It does not damage stock and if there is a disaster like a smother, stock in panic will easily be forced through it without injury.
  • It can be aesthetically more acceptable than a permanent fully battened fence.

How does a power fence work?
It’s important that you understand this to get the most out of it.
  • A power unit or energiser puts out current along the fence. The energizer can be fed from the mains supply, from a battery or a solar unit.
  • The critical part of the fence is the earth peg or pegs. They act like an aerial and collect electrons from the ground.
  • If you have a big energiser then you need a big earth.
  • The earth rule is to count 1 2 3 3. This says:
  • Have ONE continuous wire from power source to earth pegs. The wire needs to be attached with nuts and bolts and not just twisted.
  • Use ground pegs TWO metres long and knock them all the way into the ground.
  • Have THREE ground pegs.
  • Knock the pegs in THREE metres apart, if possible in a wet area.
  • The energiser should be earthed at least 10m away form telephone cables and other electrical earths including water pipes.
  • When stock out in the paddock or away at the back of the farm touch the wire, the current goes through them (delivering the shock) and back to the earth peg. The animal in effect completes the circuit and if it doesn’t, then there is no shock.
  • Modern energizers will power up to 300km of fence and at long distances, it’s important to run an earth wire along the fence to help the current find the earth contact easier.

Are power fences safe?
  • Yes they are, and they would not be allowed to be manufactured (especially in New Zealand for export to the world) if they were not.
  • But it’s a relevant question , as modern energisers are getting bigger to power longer distances of fence to be more cost effective.
  • The fence shock is normally around 4000 volts but the pulse only lasts for 0.0003 seconds which is more than enough to get a response from animal or human!
  • The pulse is very low amps. It’s amps that cause injury.
  • But saying that, a long continuous series of pulses will kill wet new-born calves if they stumble and get trapped on a hot wire.
  • There is also a risk to people who get caught up with a fence and keep getting constant pulses to their heads, especially if they are in water and well earthed. Poor state of health will increase their risk of injury.
  • Be aware about a bit of physics called “impedance”. This is the build up of current at the end of a very long power fence. So if you are at the very back of a hill country farm, you (or the dog) may find the fence to be putting out as much as 8000 volts. The dog will certainly remember the experience longer than you will!
  • If the power at the end of the fence exceeds 4000-5000 volts then it needs fixing to reduce it.
Poor fence performance check list
Client surveys by manufacturers of power fencing have found that 40% of fences are not working to their full capacity for a number of common faults leading to low voltage. Here they are, so you can check your fence:
  • Poor earth. This is top of the list and most people don’t know because they are scared to grab the fence, and they don’t invest in a voltmeter to check the power and find out where the problem is. Keep checking the earth pegs and soaking them with water frequently if they are not in a wet area.
  • Bad or corroded connections.
  • Poor knots in wire. Don’t use reef knots use a knot with plenty of twists to make good contact, or use the modern connections where the end of the wires lie parallel and are clinched together.
  • Long lengths of wire that is too thin restricting the power flow.
  • Long distances of single-wire fence (again with poor earth).
  • Rusty wire which can be a problem with salty air.
  • Animals standing on dry areas (insulated) and only touching live wires and no earth wire on the fence.
  • Leakage through poor insulation. Old plastic insulators that need replacing.
  • Leakage through excess vegetation contacting the fence. Spray the area under the fence.
  • Avoid running fences within 10m of telephone lines. Many phone lines are buried along the side of the road and may be directly under your power fence.

A meter to check voltage and indicate where a fault is,
is a lot more accurate than a bit of hand-held grass,
especially of you don't enjoy a shock.

Wire spacings on power fences for cattle


Single-wire fences
  • This is for quiet cattle like dairy cows that respect a power fence.
  • It is best suited to strip grazing where it is moved regularly.
  • Wire can be 750mm from the ground.
  • Posts can be 10-15m apart
Two-wire fences
  • This is good for permanent internal fencing for quiet cattle that respect a power fence.
  • For dairy cows or very quiet cattle spacings between wires from the ground upwards can be 350mm then 450mm.
  • You could be better with spacings from the ground upwards of 500mm and 400mm.
  • The top wire can be hot and the lower wire dead. Or both can be hot with a good earth pegs.
  • Posts can be 10-15m apart.
Three-wire fences
  • This is good for permanent internal fencing for quiet cattle that respect a power fence.
  • Wire spacings from the ground upwards can be 300mm, 300mm, 300mm.
  • The top and bottom wires can be hot and the middle one dead.
  • Posts can be up to 10m apart.

Four-wire fences
  • This is good for permanent internal fencing for bigger cattle and bulls but again assuming that they respect a power fence.
  • Spacings between wires from the ground upwards can be 350mm, 250mm, 250mm and 250mm.
  • Posts can be up to 10m apart.
  • The first and third wires from the ground up can be dead and the second and fourth hot.


Outriggers on an existing fence are a good way to
protect it from wear and tear with cattle


Extra points on power fencing
  • Before you start power fencing the farm, draw up a good plan so that different areas of the farm can be isolated by switches conveniently placed around the farm.
  • If you buy stock that are not used to power fences, then they will need time to learn. Put them for a spell in a paddock with a good seven-wire fence with a hot wire about 750 mm from the ground. Leave them in there till the feed gets short and they start fancying the feed in the next paddock!
  • If you have metal gates, make sure there are no leaks from the fence to the gate. Grabbing a hot gate is not a nice experience, especially if it’s your entrance one! Nicely-brought-up people say some funny things when they are surprised by 4000 volts!

Gates
  • These are very important and there is a wide variety of types and sizes.
  • Placement is critical to allow safe access for cattle between paddocks.
  • If strategically placed, they can be used to draft cattle in the paddock.
Good example of four gates together where paddocks join.
Can be used to move and draft stock

Disclaimer This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.

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