A Beaudesert farmer has found six cows lying dead, all in a straight line, after thunderstorms in south-east Queensland.

Derek Shirley said there was not a mark on any of them.

"There was just a storm, it was a pretty severe storm, there were a few cracks of lightning and thunder and then there was one particularly loud one and that's all we heard," he said.

But he did not check the cows until a few days later.

"They were blown up by the time we found them," Mr Shirley said.

"Our first thought was that they had been poisoned, but they don't just lay in a line like that.

"The strike has actually thrown them into the fence, like some of them were through the wires."

Mr Shirley estimated the four cows and two calves were worth about $10,000.

A blast similar to an explosion

ABC science expert Dr Karl Kruszelnicki said he had never seen cattle moved by the force of lightning before.

"What astonishes me is their heads are all through the wire, they have been blown there and that is not something I have come across before," he said.

"To do that you would need a huge blast of air, because a cow is not an insignificant beast, it is not like a cat weighing three kilograms, you're talking hundreds of kilograms."

The cows are theorised to have all suffered a simultaneous heart attack caused by an electric field. ( Supplied: Derek Shirley )

Dr Karl said water expands astronomically when heated and this may have provided the force to push the cows into the fence, but it would not have killed them.

"When water heats up and turns into steam it expands in volume by 1,700 times, that's huge," he said.

"That would have provided enough of a push to blow the cattle into and sometimes through the fence."

Possible simultaneous heart attacks

The force of being pushed into the fence is not what killed the cows according to Dr Karl. His theory is that they suffered simultaneous heart attacks.

The cows had an estimated value of $10,000 ( Supplied: Derek Shirley )

"When the lightning hits the ground you get a spreading of an electric field," he said.

"Assuming it happened behind the cattle and they're facing into the fence, at their back legs the electric field is, we'll just have a guess, a million volts per metre and it weakens and at their front legs say half a million volts a metre.

"The electric field goes in through their back legs, through the body and down their front legs and in-between is the heart and they have a heart attack."

But for the cows it would have happened very quickly and it's unlikely they would have felt any pain.

"Brief instantaneous pain, at the most they would have been conscious for six seconds, and then they'd go unconscious," Dr Karl said.

"But almost certainly they would have gone unconscious immediately, so at least they weren't in pain."

He also pointed to a case in Dorrigo, New South Wales where 68 dairy cows were killed by a lightning strike in 2005.

Dr Karl said this was another example of electric field causing mass heart attacks.