Take her into the house immediately and put her in a warm bath with Epsom salts if you have them. She's probably in shock and will thus not drink the bath water. (Stay with her the whole time to make sure she doesn't drink the water or drown). Dilute povidine iodine in a cup of warm water and gently pour it over her wounds. Then rinse the wounds again with cups of plain warm water. Ducks get really cold really quickly after attacks and have difficulty keeping up their body heat after flesh bites/feather loss so let her stay in the warm bath for quite a while until her head is in an upright position and she is displaying more interest in what's around her. (They tend to bunch up and bend their heads down in front of themselves when they're we cold or under duress). Gently lift her out of the tub and place her in a warm towel. Place her in a towel lined box in a warm room in the house. Turn on a space heater (on a safe and low setting) for about a half hour to help her dry while patting her carefully with a hand towel. If you can get a vet to prescribe Gentamycin spray (60 ml) you could spray it over her wounds twice to 3 times daily once she's dry. If not, you can apply Neosporin ointment, however that is still not ideal because it is painful for the ducks to have ointments rubbed on wounds. A Gentamycin spray would be more effective but that can only be prescribed by a vet. I would keep the duck in the house in a room safe from other animals or drafts for as long as the wounds are severe. Once they have healed and feathers grow back she could be put back outside and you could spray a light coating of AluShield, which you can get at most feed supply stores. I really hope your Rouen recovers fully over time. I can empathize with how frightening it would be to find her injured and wounded. Remember, if she seems to be weakening she could develop a bacterial infection from the attack. It would be best, if you think she is battling an infection, to take her to an exotic or Avian vet. I know they can be expensive but it's well worth the money and can be a life saving decision in the end.
