Animal, I would assume that the black thing was bad and needed to come out. As far as how big to cut the circle, I'm waiting for a set of those biopsy things. I got a set of different sizes on ebay for $19.
My last one was when I removed the plug, I got some pus. But 2 days later after the Epsom paste poultice, I messaged the foot and a kernel popped out. Seems like the poultice drew it close to the surface so it could come out.
Nothing like a good poultice!!!
WOW that's good to know just in case my roo does have bumble foot. Not sure right now so on here reading so I will know what I need to do. Vet looked at it and thinks it's a callus and it's like a ball under there with a small black spot but not crusty and not real black, more like light black and not crusty looking. BUT a huge ball like thing under his foot. He gave me something to put on it 2x a day and said if it wasn't better in 2 weeks he'd have to remove that ball and then pull the skin over the hole and sew it up. Afraid that might get expensive.

IF I have to do any surgery on him myself (I HOPE I DON'T) I have some sovereign silver I'll put in the hole before I put the wrap over it. Read on another forum where people were using sulfur tablets for humans I'll post the message here since I cut and pasted and saved it in case I need it. Going to buy some sulfur tablets tomorrow along with clear iodine and vet wrap and betidine if I can find that. See below........I just don't know about leaving it open though. I think I'd HAVE to bandage it.
I asked him to look at a hard spot on the pad of her left foot that had a black scab on it.
He removed the scab and confirmed a small ulcer underneath, the very early beginings of what could turn into
bumblefoot. So I asked was he going to give me antibiotic creams and would I have to bandage it. He advised me
that the top chicken experts in the UK now advide NOT to bandage the ulcer, but to leave it open, keep it dry,
wash twice a day with hibbiscrub AND to add sulphur to their diet for 3 weeks. He said to get a sulphur tablet
supplement ( for humans) grind up 1 tablet and put a few grains in her food over a 3 week period. using up the
1 tablet over that time. Along side this to give her oral ABS, to kill any infection.