barn?
Barns are used to store feed.
Maybe they were feeding them where the food was stored, and if they were feeding them with grains then it is possible we got a "flour air explosion" or equivalent for whatever the food might have contained.
But
@Bear Ribs s explanation sounds plausible.
I mean, I think most of your cows are grass or soybean or corn fed, and those are IIRC not as explosive as wheat and flour.
At least I haven't heard of a corn or soybean silo going boom the way wheat and flour storage facilities sometime do.