I have a new flock of hens coming next week and while cleaning out the area in and around the hen house, I came across a large mound of composted earth containing sheep bones, skulls, etc. The former owner raised sheep and they had a bunch of lambs that didn't survive one year (from weakness and lack of care, not disease.. I believe). The pile is fully decayed, 2+ years old. I was hoping to give my hens access to the pile to scratch it up and turn the land but now knowing that it was in fact an animal graveyard, I'm wondering if it is safe to have the hens picking at the pile. Any advice?