Today we went out for the address, and walked the property line (deeper than what we ever have before; which made it obvious it's a much larger property than we imagined). While on this walk we found what looked like an old burn pit, with partially-burned hay, dirt, and other things all over it. My friend pointed and said, "Is that a rib?" We pushed the hay around, and found the remains of a horse under an old tarp.
I know that there are laws regarding the disposal of dead animals. Would we need to follow these for the bones of horses long dead, as well? A third friend ("outside eyes") mentioned just burying the bones.
EDIT: To clarify; we found a lot of churned-up (partially buried) bones, skulls on the porch, and the horse under the tarp. I saw no flesh. Other bones are, literally, laying around the property.