When a chicken moults their old feathers fall out and new ones start to grow to replace them. A new feather growth is known as a blood or pin feather. It starts off looking a bit like a porcupine quill and can stay like that for 5-7 days before the shaft starts to flake off and the feather starts to open and grow. Once the feather has fully matured (which can take a couple of weeks) the blood inside the shaft recedes and the feather becomes a normal feather which is hollow inside.
During the initial growth process, the shaft of the feather is basically an open blood vessel to provide the needed nutrition directly to the feather so it can grow. The problem with this is that if the feather gets split or broken off completely, that blood vessel is still left open, and because it cannot compress and close itself like skin would the hole remains it's full size - and that can make it much harder for the opening to clot and the bleeding stop.
The beginning of new feather growth - in the 'porcupine quill' stage. These pin feathers / blood feathers are essentially blood vessels and are very sensitive - it can be very painful for your chicken if they knocked or broken (and will bleed a lot!)
WHEN THE FEATHER HAS A VERTICAL SPLIT
If it is a vertical split then often the split can be sealed up so that the feather can continue to grow and hopefully after a week or so you will still end up with a beautiful feather. This scenario is preferential to having to lose the feather completely and then start the whole process of growing from a pin/blood feather again.
What you will need :
A piece of gauze
Surgical glue (even Krazy glue would be ok because it doesn't need to be sterile).
* An extra pair of hands may also be helpful!
Surgical glue and/or Krazy glue does not work well when it's wet, which includes blood, so the first thing you need to do is hold your feather and then use your gauze to wipe away the blood. Then apply your surgical or crazy glue along the split. Use two or three applications for extra security (let the first application dry, and then apply some more glue, let it dry again and then apply the glue again). Each application will probably take about 30 seconds to dry.
Try not to stick all the other feathers and yourself to your chicken!
WHEN THE FEATHER IS BROKEN OFF COMPLETELY
What you will need :
(if you cannot get the bleeding to stop)
A piece of gauze
Stop watch / clock
* again, an extra pair of hands may also be helpful!
Sometimes the feather may have been broken off completely so that you are left with part of the shaft. Because the shaft is holding the vein open it will be hard to stop the bleeding as it is, and so you will need to remove the shaft of the feather completely using your forceps.
With one hand hold the skin firmly where the feather comes out of it to prevent tearing the skin. Then with the other take your forceps and take hold of the feather shaft along it's length so you have as much surface area of it as you can in the forceps, and are as close as you can get to the skin without pinching it. Clamp down and then pull straight out (don't wiggle or angle the forceps). You should now be left with the follicle which is the soft tissue part of the vein - it will still be bleeding but because it is no longer being held open by the shaft it can collapse. You will need pressure to stop the bleeding, so hold the follicle for one minute (this is best timed). Then let go and watch it - often, if you pluck the feather shaft and hold the follicle for a minute the bleeding will have stopped and that is all you have to do. If it is still bleeding hold it again for another minute, and then watch it again. If after five times of holding it for a minute it still has not stopped then you will need to seal the follicle.
To seal the follicle you will need to use surgical glue (because it is inside the follicle it has to be sterile). Hold the follicle shut, wipe away any blood with the gauze, and seal with the surgical glue. As the follicle exfoliates the surgical glue will just fall out and so in a couple of weeks it will be gone.