This makes no sense.

Do you know how much area 18,000 cows takes up?
That isn't one barn.

And all of the huge, modern farm structures are all metal.
What burnt?

There could have been a giant methane fuelled fire ball
But the most that could have done is kill the cows from asphyxiation.

Either the fire was bogus (as in, someone came in with a lot of explosives and/or combustibles)
or the cow death head count is bogus.

This story has a lot to answer.