Bumblefoot is fairly common in chickens, and it's a name sometimes given to any foot problem. We're referring to it as when chickens get swollen, pus-filled scabs on the bottoms of their feet. It's painful to walk on, and the infection can spread and require toes or even legs to be amputated.
The cause: Bumblefoot often just happens because chickens fly off their roosts and land on a hard surface, distressing their feet. It can also happen from chronic life on hard floors or wire floors.
Diagnosing: If the pad is very swollen, hot, taunt, etc. then there is probably an active infection going on and a vet can surgically open them. Some chickens will have old bumblefoot scabs that are hard but aren't causing them any problems; after these scabs fall off, the chicken may be left with larger, soft, flabby pads. This is fine. We do a whole-body check every six weeks on the chickens, which includes looking at their feet. If they have a new scab on their foot pads, then we usually just treat them ourselves. We haven't had any so infected that they've required vet care. Use your best judgment.
Prevention: We put extra straw around their roost in their coop as well as some easy-to-clean carpet remnants by the coop door, where they especially like to land and where straw quickly gets pushed aside.
Treatment: Farm Sanctuary packs their feet with an medication called Quartermaster for cattle that's only available by prescription. We didn't have access to this so we made up our own treatment, which worked great, and when we told our vet what we did, she gave it the thumb's up. We sprayed the scab with hydrogen peroxide, packed in a little triple-antibiotic ointment, put gauze over the scab area and wrapped it with vet tape (see picture at right).
The triple-antibiotic is available at any grocery store; you just squeeze some on the scab.
As for the gauze, one problem is that it causes the chicken to walk awkwardly. So our wonderful vet instructed us to cut a little hole in the gauze for the lump to sit in so that the chicken's foot sits more flatly on the ground.
Be sure to have the gauze COMPLETELY engulfed by the wrap. Gauze loves to soak up any wetness like a sponge, and if the gauze gets wet, you need to change it.
We did this treatment with fresh wrap and gauze twice a week, and Ally's sores were gone in two weeks.
Taking off the scabs and squeezing out pus: It can speed healing to open up the scab and squeeze out the pus inside. (You do this before putting on the hydrogen peroxide.) The problem here is that in a chicken pen, it's easy for outside bacteria to get inside the foot if you break it open. We used tweezers to pull off parts of the scab until there was a little opening that allowed us to squeeze out the thick, sticky pus. This worked for us, perhaps because we were diligent about disinfecting the area and changing the dressing twice a week. Our vet suggested another way of doing this that we have not tried yet. She said we could soak the chicken's feet for 10 to 20 minutes in water with a little Betadine in it until the scab peels off easily.