A lightning strike killed 68 dairy cows waiting to be milked on an Australian farm.

The farmer, Warwick Marks, 57, said the lightning strike killed half his herd of 150 Jersey cows at his dairy farm outside Dorrigo in northern New South Wales state.

"The bolt came through the roots where they were standing; 68 were killed outright and another three looked like they were gone as well but they were just stunned and came good a bit later," says Marks, who arrived on the grisly scene minutes after hearing the thunder clap.

"I was expecting it would be bad, but not this bad," he adds.

Sixty-eight cows were killed by lightning, but another 69 survived.