You are correct, however this wound is fatal. The vent has been completely removed. Honestly she is suffering right now, and there is no way to repair this type of damage. I have performed surgeries on prolapse hens successfully, the vent for this girl is completely gone.
That is not from a dog, unfortunately hens can be aggressive to other hens. They will sometimes do what you pictured to another hen. This is also a fatal wound as the vent has been removed.
