Treatment for Tail Torn Off?

Unless the others are pecking at it, I'd leave it alone.  If they are pecking at it, you might practice some minor surgery and suture it shut and put some blu kote on it.

also petroleum jelly is a wonder drug for chickens and turkeys to keep them from pecking at something you don't want them to. Since it's bloody I'd start with an anti-bacterial ointment based in petroleum jelly.. they hate the taste of it and it will keep it clean from dirt as well. Good luck!

It's amazing what these birds can suffer and recover from! Good luck to you and your newly rumpless australorp!

If you can obtain it, try to get some Silvadene ointment. It's a remarkable healing and infection preventative agent.

Last summer I had a tiny chick get scalped to the point she had a gaping wound on the entire back of her head. It healed without ever getting infected, even though I kept her in the brooder with the others.

The critical things you need to do are clean and disinfect the wound twice a day with peroxide. Then keep a moisturizing antibiotic ointment on it, NEVER allowing the wound to dry out! Blu-kote simply isn't adequate for this purpose.

Keeping the wound moist is the most important. The tissue will regenerate as long as it's kept moist. If allowed to dry out, it will become infected and will quit forming new tissue.

As another poster pointed out, these critters are incredible survivors. Wound care is tedious and time consuming, but well worth assisting your little victims in their struggle to heal.

Peroxide is not a good thing to keep putting on wounds.  It damages the tissues.  Clean wounds with  soap and water first being sure to flush them out well.  Then you can use a betadine solution or something similar to flush with.  Then put Neosporin ointment generously on it and cover.  Clean and change bandages twice a day until you see it healing up...then you can just change the dressing once a day putting new Neosporin on it each time until it's substantially healed. 

Here's an excerpt from this site http://en.wikipedia.org/wiki/Hydrogen_peroxide :

It is a common misconception that hydrogen peroxide is a disinfectant or antiseptic for treating wounds.^[35][36] While it is an effective cleaning agent, hydrogen peroxide is not an effective agent for reducing bacterial infection of wounds. Further, hydrogen peroxide applied to wounds can impede healing and lead to scarring because it destroys newly formed skin cells

I wouldn't worry about using peroxide to clean and disinfect wounds. It's commonly used as such by vets. In fact Betadine is just as toxic, if not more so. Either one, though used to clean, but not left on the wound, is effective and safe.

If you can get ahold of Silvadine, it's a very effective healing and anti-microbial. It allows the wound to stay moist and protected and promotes extremely fast healing. It's what I used on my scalped chick, and she had no tissue at all covering the back of her head as the attempts I made to stitch her failed. 

It's even better than Neosporin, and probably much safer for chickens.