John L -thanks for the reply. When my dog was ill, I brought him to the vet, they took a syringe and needle and injected fluids (maybe saline, not sure) just under the skin between his shoulder blades. The result was a huge 'ball' of fluid under the skin. The vet said that this was the second best way to get fluids in an animal as it will be absorbed. IV being the best but not possible in this case.
Secondly: A friend of mine had a pregnant goat that refused to eat and drink, it was becoming dehydrated and the babies stopped moving. This method was used again, injecting fluids under the skin to be absorbed by the body. Within a few hours of treatment, the babies began moving again and the goat seemed not as 'sickly'. This treatment was given to this goat a couple more times until she would drink on her own.
My fear is that my hen will get too dehydrated if her crop is impacted. The crop right now is so large it covers her whole chest and it is rock hard. She is pooping very little and feels thin. Being hydrated is so important to sickly animals. I am just trying to get info on anything I can so I can save this hen. It is my son's first hen, she is 4 years old. He is so upset right now. Thanks again for your response.