Saw this happen to a herd of cows in Alabama one time. Lightning struck the tree they were all huddled under to get out of the thunderstorm.
They were just ‘dead’. No marks, burns, etc.
The big oak tree however was just split in half.
I suspect a dry lightning strike too.
Sobering.
I saw the same thing in a herd that was hit by lightning under a tree. They just looked like they went to sleep.
Here if its not lightning, and there are pumps pulling up oil on the property, and the farmer is too cheap to put a fence around the well, the cows sometimes go to lick accumulated salt off the oil pump and get clobbered as the counter weight comes down. Dumb animals, but we’re not breeding them to be smart.
Other possibilities; they ate something like water hemlock or deadly amanitas. The argument against that is that they would have taken a while to die and could presumable texted or wrote a message. Unless it was multiple suicides or murder / suicide by poisoning, lightning sounds about right.