Friday, March 29, 2024

A shocking problem

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At the February meeting of the Stratford Demonstration Farm committee there was some discussion about the poor results from the recently completed pregnancy tests.
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These gave an empty rate of 12.5% which was particularly disappointing in view of the excellent condition the cows had been in at mating. During the course of this discussion I enquired whether there had been any significance difference in empty rate between the first-calvers, which had been grazed off the farm, and the older cows.

When asked why this might be significant, I explained this was one of the classic indicators of stray electricity on the farm. I quoted an example from personal experience of a case where a small fortune had been spent on soil, herbage, and tissue analysis on a farm where the heifers came home from grazing in rude good health, 100% in-calf, with no trouble, in contrast to the cows on the home farm which regularly had an empty rate of 30%-plus.

My suggestion that the farm be tested for stray electricity established that this was the problem and the solution was simple and inexpensive.

The problem of stray electricity on the farm is one of which there is fairly widespread ignorance and neglect, yet its impact can be horrendous. Probably contributing to this is the fact that cows are about 10 times more sensitive to electrical shock than humans.

And they don’t wear gumboots. Cows will feel as little as a half volt while humans wouldn’t even notice it.

Stray electricity can affect not only reproduction, but also production, udder health, temperament, and general wellbeing and health.

Stray electricity can be caused by:

[BLOB]Direct voltage leaks from faulty electrical equipment and/or wiring.

[BLOB]Spike electricity, which is a short duration surge of voltage caused by the switching on of electric motors, water heaters etc.

[BLOB]Leakage from electric fence units. This is by far the most common cause and is usually caused by poor earthling. It will show up as spikes of voltage at about one second intervals

General cow behaviour can give a very good indication of stray electricity. Some things to watch out for are:

  • Cows being reluctant to enter the milking area from the yards, or the yards from the race. They may bend and sniff the approach as they come up to it and then back away.

  • Agitation and discomfort when the cups are put on.

  • Slow let down of milk. Milk only dribbling out at first and a delay of 30-60 seconds before a steady flow is achieved. In bad cases this might take three to four minutes.

  • Strong and continued resistance to daily drenching. Cows will generally be fairly happy with daily drenching, and will have quickly adjusted to this, but not if they are getting an electric shock each time.

  • Excessive dunging and urinating, particularly dunging. A classic example is a faulty backing gate giving a spike in electricity as soon as it’s switched on. When this happens the cows become agitated and defecate in unison.

  • Cows stepping around and avoiding sections of the race, or speeding up when travelling over them. Leaking underground cables from the electric fence system would almost certainly be the problem here.

  • Generally sniffing or tentatively lapping the water in the trough and only reluctantly drinking it. This means voltage in the trough.

If any of these things are occurring remedial action is obviously required but there are also a few tips that will help ensure the problem never arises.

Firstly, only have electrical gear essential to milking in the dairy and ensure that it is well earthed. This applies particularly to the drenching system as the inside of a cow’s mouth is particularly sensitive.

Never, never, never put an electric fence unit in the dairy. Make sure the electric fence unit has its own, individual earthing system and that this is functioning perfectly.

Even if you are 100% sure the electric fence system is performing safely it’s still a good idea, as an extra insurance, to switch off the energiser during milking. This can be done automatically, and very cheaply and easily, by installing a timer.

As far as the constructional characteristics of the dairy and its environs, including yards, milking area, and milk room, are concerned all structural metal should be bonded together and well-earthed. They should also be connected to a bonded-in mesh under the yards. This should have been done during construction, and generally has been. However where it hasn’t, it can still be done by cutting slots in the concrete, laying copper wire in them and plastering the slots over.

While the system may be perfect now there are many places where things can go wrong – deterioration and wear and tear will always occur over time. Regular checking of the whole system should be carried out. The annual machine check is an obvious time. If there’s any suspicion there’s a problem an immediate check is indicated which a competent person can carry out in about 30 minutes.

It is most likely that a malfunctioning electric fencing system will be the source of the problem, and the most likely cause will be poor earthing. I can recall more than one occasion where the problem was tracked down to a neighbour’s electric fence.

So I will conclude with the story of the electric fence dealer who arrived at a farm in response to a complaint that the electric fence energiser recently sold wasn’t performing particularly well. Neither the farm nor the farmer, it must be said, seemed to exhibit a particularly high degree of competence with an undrained swamp near to the implement shed, beside which was a plethora of wrecked farm machinery, old car bodies and other junk.

The problem was quickly identified as a poor earth, and the electric fence bloke, in a flash of inspiration, suggested an ideal earth would be obtained from tossing some old car bodies into the swamp, which the farmer agreed to do.

Our expert was somewhat chagrined to get an irate phone call a few days later complaining the system was no better, so customer satisfaction being paramount he revisited the problem. Once there he had to tactfully point out the new system would be perfectly satisfactory when the earth wire was actually relocated and firmly connected to the car bodies that had been diligently dumped in the swamp.

 

* Standards New Zealand has just published a new handbook on electrical installations in dairies, SNZ HB 6117:2014, giving the recommended trade practice for building dairies to minimise stray voltage.

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