Marble-sized growth under vent! WHAT is it?

[homeschooler]

Does anyone know what this could be??? one of our 9 day old chicks has a large growth on his rear end. it has black pus-like stuff in it and looks like he's been chewing pieces of it off. it is marble sized and black. it's right under to the left of the vent. i separated him from the rest of the chicks. I started using vetericyn hydrogel spray on it. is there anything else i should do?

thank you for your help!
Angela

 

[feathers_3]

It could be unabsorbed yolk. I recently had a 4 day old chick that I noticed had an unabsorbed yolk and it is beginning to go away.

It sounds like whatever it is may be infected, hence the pus. I would use an antibiotic ointment or spay and just keep it clean and dry. It's good that you separated it.