Yes I think it’s a breast blister. Do you know what causes these? I am not looking forward to cleaning this out.
In our case the rooster (who we just rehomed from some poor conditions) has weak legs and sits down a lot which put a lot of pressure on his body. He was lying just on a dirt floor all the time. We are hoping he will roost, once he gains strength, and for now we have him on a thick layer of clean bedding and with the bandaging quite well-padded.
Cleaning it out was easier than I’d thought and your hen’s wound looks similar. What I wasn’t prepared for (and which makes total sense) is that only about half of the lump could be cleared out - the bottom half of it is just swelling, inflammation of the sternal bursa if I understand correctly.
I used clean tweezers (only used for my animal first aid kit) and another little metal tool, all cleaned with chlorhexidine surgical scrub, to gentle pull away/out the pus, then I flushed the wound thoroughly, packed some triple antibiotic ointment in the hole and bandaged. The bandaging is the most difficult thing in my experience so far, since it’s hard for someone to hold them still whilst you wrap around their body under the wings. I’m about to experiment with a stick-on dressing later today which I think might work since the skin around the wound is bare. I’ve ordered some dressings designed for pressure sores in people but they’ve not arrived yet.
I had my fiancé hold the roo and we did it when it was quite dark (I had a head torch) to help keep him calm. It was my first time doing something like this and my tips would be to prep all your equipment and the space before getting the hen involved, to limit time and stress to her, and to be confident in what you are doing. From reading many posts on here over the years, and with
@casportpony sharing info with me on my original thread, I kinda knew what I was dealing with and was able to get the job done without too much fuss which I think was good for us all.
That was Monday and we checked and applied a new bandage on Wednesday. The bandage looked and smelled really clean and roo has been eating well, but I removed the scab (thinking it looked very similar to original wound) which I think was a mistake. Underneath it was all very clean. I flushed, dried and applied more ointment and a fresh bandage - I’m hoping today that it looks similar and this time I will leave the scab and just apply ointment and a dressing.
Hope that helps and good luck. Oh and wear disposable gloves!