The cows' owner, Derek Shirley, said he was "stunned".
Sabrina Lomax, a livestock expert from Sydney University, said she believed all six animals had been touching the fence when they died.
"In these sort of freak accidents, it was just an inconvenient placement of the animals in regards to the (lightning) strike," the BBC quoted Lomax, an animal behaviour and welfare researcher, as saying on Thursday.
"They would have died instantly from a massive heart attack."
Shirley, whose farm is about 70 km south of Brisbane, said he initially thought the cows had been poisoned.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)