Call to check stray voltage in cow sheds

Otago Daily Times

24-06-2025

An Ashburton farmer is advising dairy farmers to get their milking sheds checked for electrical faults after leakjing power was found to be making his cows "twitchy". Tim Cronshaw reports.
Canterbury dairy farmers have found their "twitchy" cows are getting shocks from electrical faults in dairy sheds by voltage leaks up to 60 times above recommended levels.
They are advising other farmers to get their sheds checked by professionals using peak voltage meters and oscilloscopes to trace voltage differences in a two to three hour test.
Distressed cows reluctant to go on and off platforms are excreting more, prolonging milking times and becoming susceptible to mastitis as they would rather retain some milk than get a shock when the milk pump starts to operate.
Stray voltage is caused by wiring failing to be earthed properly or two surfaces conducting electricity.
Small electrical currents make contact with cows through metal pipes and rails in the dairy shed and they become agitated by the tingle or mild shock.
Ashburton farmer Willy Leferink was aware of the risk of electrical shocks when he was in the Netherlands and began noticing his herd displaying unusual behaviour in the rotary milking shed.
The cows were defecating just before they came into contact with a teat sprayer and this was traced to a live reading of 3.8voltage, he said.
"The cows sensed any minute they were going to get a shock so the first thing they did was a number two.
"That creates a lot of mess and is not good for the cows.
"We fixed the issue with a copper piece in the line to neutralise the voltage to the frame so power would go through the frame and not to the cows.
"At the following milking not one cow defecated and the cows were a lot calmer."
Another voltage issue preventing "scared" cows from going on the platform was also sorted.
"What happened was we cut about 20% off the milking time.
"For me that was an hour per day and for bigger sheds that might be more. That means staff can do other work and the cows are relaxed. I always felt the cows were a little bit tense and twitchy when you touched their udders and that's all gone."
Mr Leferink said the shed wiring was earthed when it was built in 2012, but some of it had likely corroded.
The cost of electrical repairs was "chicken feed" compared with quicker milkings, less water used to wash down the shed and having happier cows.
He said many farmers would probably have no idea they had stray voltage and this was becoming more likely as farm electronics increased in sheds, fencing and irrigation.
"I was trained in this field back in the 1970s and particularly in our area there was a big problem because the Germans didn't earth their power generation properly.
"It was feeding back underground into the power grid east of the Netherlands and when they started developing free stalls and steel was involved all of a sudden these cows were getting shocked.
"A cow can feel 0.36voltage and we found 20volt on our platform and wondered why the cows didn't want to come off the platform."
The 0.364volt is based on research finding this is when 10% of cows exhibit a negative reaction.
Electrical circuits put in by contractors had met building codes when the shed was first built and he had earlier brought in since-retired inspector Brian Rickard to check for stray voltage and fix some of the problems. Since then, teat sprayer and variable-speed drives had been put in.
Continuing to sense the cows were unhappy, he got his electrician, Lawrence McCormick, who had since bought Mr Rickard's Stray Voltage Solutions business, to test the shed again.
Mr McCormick said he had been the electrician on the farm for 10 years and, without the correct test equipment, had no idea anything was wrong.
"I believed that everything was OK because when they pushed 'go' the machine started and the cows got milked.
"I tested the way Brian taught me with the gear I purchased off him recently and we found quite a few problems and the best thing is that I have found solutions to them."
Mr McCormick said there was a lot of leakage from variable drives and voltage differences between weigh scales and the rails around the yards.
The teat spray was live so cows were getting live liquid put on to them on the last four or five bales before they came off and this was causing them to defecate, he said.
"Cows are flight animals so when they think something will hurt or go wrong they will run away and the best way to run away fast is to lighten the load."
He said extra steps were taken above the electrical code to improve the wiring of the drives and remove voltage from the equipment.
"We fixed the earthing and put in filters and ferrites [chokes] which are like the little lumpy bit on the cable before they plug into laptop chargers.
"Every switch-mode power supply in New Zealand is supposed to have one of them.
"So your variable-speed drive is just an over-size switch-mode power supply.
"The results have been unreal."
Most rotary sheds have variable-speed drives on the platforms, vacuum pumps and milk lift pumps and some farms have them on meal feeders.
All of the 40 dairy sheds he has tested since March have showed faults to varying degrees.
"I can tell by the quality of their stock and the ways their properties are maintained that the farmers who are getting me in obviously care about what they are doing and just don't know there was a problem."
[e-mail]