Stray voltage a negative for dairy cows
Meridian Energy has increased milk quality and reduced the milking time at a dairy-shed in Kurow, North Otago, by
eliminating stray voltage in the shed.
“The large electric motors used in modern dairy sheds often mean there is a small voltage running across the concrete
floor of the shed, which cows can feel,” says , Meridian’s Rural and Business Segment Manager.
At a Kurow dairy farm owned by Meridian Energy, this stray voltage was found to be around 1.5 volts. Cows can feel a
voltage as low as 0.4 volts.
“As a result, the cows would not come easily into the shed, they would sniff the ground, would not cup up easily as a
result of teat retraction, or would kick the cups. They would also tend to defecate in the shed, and be under stress as
a result of this stray voltage.”
People working in the shed could not feel the voltage because they usually wore rubber gumboots.
“The solution was to run a 4mm thick copper ring around the concrete rotary bale in the shed. This was set in the ground
at a depth of 400mm with a 2m long stainless steel peg every 5m or so,” says .
This innovation has eliminated the stray voltage in the shed. Nearby farm houses or other buildings with electrical
appliances can also contribute to stray voltage in dairy sheds.
“The sharemilker and three staff used to take four hours to milk the cows. Milking time has now dropped to around two
hours,” says .
The reduction in stress levels of the cows has improved the quality of the milk, reflected in a lower sematic cell
count.
“The shorter milking means less energy use and therefore improved energy efficiency, with the added benefit of lower
energy costs to the sharemilker,” concludes .
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