Chicken has Bad Wound

[Strozerkat]

One of our hens has a pretty nasty looking wound and I'm wondering how I should be caring for it. This is our first year having chickens so we may have made mistakes. I attached a photo for reference. We have 6 hens and 1 rooster. They are 7 months old. We weren't told the breed when we got them as chicks so I'm not sure what they are.

We first noticed a week ago that some of the other hens were ripping out her feathers. Then one day when I went to check on the flock free ranging in the yard, I noticed 2 of them were missing. I went into their coop to see the rooster sitting with his head low and cooing at me, sitting next to the hen who was getting picked on. He put his head in front of her when I tried to go near her. When my fiance went to check, he brought her in the house and showed me a wound under her wing. Since they free range in the yard, we were unsure if she was attacked by an animal or if the hens did this to her. The wound didn't look too bad at the time so we decided not to separate her, fearing that would cause more issues down the road. Instead we kept her locked in the coop so she and the others were only together at night. A couple days ago we checked her wound and it looked like there was a whole chunk of her missing. I can only assume the other chickens have been pecking at it and making it worse. So we decided that day to build a small makeshift coop for her in the spare room in our house while she heals. We got an iodine spray and have cleaned the wound with saline. It's looking better but still doesn't look good. She is behaving normally and doesn't look like shes feeling ill at all. I am wondering how we should be properly looking after the wound and also if it is possible she will recover from this. It looks really bad to me, though my fiance is more confident.

I also have a couple side questions. I want to know why they are behaving this way. I am worried they are going to keep picking on the hen at the bottom of the pecking order and slowly kill off the whole flock. Since removing the injured hen, they are going after another hen. The rooster is quite docile and calm do he doesn't stand up to the more aggressive hens. I feel like they have plenty of space in their coop with nesting boxes and many perches. It's a 12ftx6ft room inside our barn. Is that maybe too big and making them feel uncomfortable? They have also gone through a recent stress. We had gotten 2 batches of unsexed chicks and ended up with 4 roosters, 3 were slaughtered a couple weeks ago. They were being too aggressive towards the hens and it became a huge problem. The flock seemed to be doing well for a few days after the roosters were removed, the rooster that we kept seemed to be grieving for a short period but the rest were doing well. Then all of a sudden the biggest hen started crowing and bullying. I'm 99% sure she is a hen, she shows zero characteristics of a rooster other than her recently starting to crow. Even so, her crow sounds off and doesn't really sound like a rooster. We got jackets for them so they aren't able to feather pluck but obviously those cant stay on forever. I want to know how to help them all make peace and become more comfortable.

Any help is greatly appreciated! I am very confused on how to deal with this situation.

 

[Strozerkat]

Oh btw, the iodine spray is specifically for chickens. We got it from the local farm store.

 

[coach723]

The wound looks like possible rooster damage from being mounted. Once a bird has a wound it will attract pecking by others and can be made much worse. Any blood or open wound is going to attract pecking. At 7 months old you have a cockerel rather than a rooster (not a roo til 1 year old) and cockerels are immature with raging hormones and can over mate and hurt hens in their exuberance. Some calm down with maturity, some are still rough. 6 hens to 1 rooster is a low ratio particularly for a young cockerel, a better number is about 10, to prevent over mating. The 'real' number is very dependent on the actual cockerel/rooster in question. Sometimes fewer hens can work, sometimes they need more. More docile, submissive hens can still end up being over mated and look rough or get hurt. If necessary you may need to separate the cockerel until he's a little older and calmer (hopefully).
When they are not in the coop do they free range? How much space do they have? Not enough space is often a reason they do this to each other.
I would apply plain neosporin or plain triple antibiotic ointment to that wound a couple of times a day to keep it covered and moist. If any feathers are getting in it then trim those back with small scissors to help keep it clean. As long as it's not infected it will heal with some time, it may take a while. If it needs to be flushed out again then I would use a chlorhexidine solution (hibiclens-any walmart or pharmacy) or veterycin spray (any pet store in the dog/cat section)and then apply the ointment. I would keep her separated until the wound is not a pecking risk. If you have a wire dog crate then she can stay in that in the run with the others, so they can all see each other but she is safe, that makes reintegrating her easier when it's time. If flies are an issue (as they can be in a barn) then you will need to be vigilant about making sure they don't get to her wound and cause flystrike, which would make everything much worse.
This thread has some pictures of wounds during the healing process, might be helpful to know how they look:
https://www.backyardchickens.com/threads/wounds-pictures-of-how-they-heal.1325817/#post-21627607