just the other week I found a small nail brush in my haylage and a small rusty metal hinge of sorts, and another livery was filling nets and a small torch was wrapped in the hay bale...
I haven't come across any dead animals wrapped in my hay/haylage however the yard cat does like to kill rabbits, halve them and leave them lying in your hay, found the bottom half of a rabbit the other week, perfectly intact...
Years ago I lost a ring up at the yard. I still dont' know what happened, I just looked down at my hand and realised it wasn't there. It was just cheap thing from Accessorize so while I was slightly miffed, I didn't worry about it. About 3 years later I was filling haynets and found it in the middle of a bale of haylage. It must have come off my finger in the field and then got baled up with the hay!