My mom accidentally pulled one of those off thinking it was pasty butt once. When I got home she was just about in tears thinking she might of killed it. She said "One of the chicks had this thing on it's bottom and I thought it was poop and I pulled it off and it bled! There was a hole or something under it!" I went to go check it out and I couldn't even figure out which one she had done it to. They all looked normal.All of the chicks I received this morning seem perfect except one little Delaware (?). I think she still has her umbilical cord attached but it is a bit larger than I imagined it would be. I think her vent is not covered but I just want to make sure it is not pasty butt. I did gently wipe her bottom with a warm, wet washcloth. She seems OK (has eaten and drank) but is more sleepy than the other chicks. She keeps wanting to sleep on her side and the other ones want to pick at her little sore bottom!
Here's a pic:
I think the green color is from the Oasis feed supplement Meyer gives the chicks prior to shipping.
So don't pull it off. It bleeds and makes you sad. But it apparently doesn't hurt them.