I have some canned goods that I'm not going to eat, some of them are soups and they say they have 400-800mg of sodium in it. I breifly remember reading something that too much sodium for a chicken is not good.
When I want to serve something like stale tortilla chips I soak them repeatedly and rinse away as much salt as I can. Most chicken feed has at most 0.5% salt. I would not feed salty soup but if it is chicken soup I would consider rinsing it out several times and soak the contents, then feed just the solids. It may not be worth the trouble if it is just a bit of chicken in the can or mostly liquid. I would not feed salty soup as it is though.
x2...I wouldn't do it. Soups have a LOT of salt. I forget what it is that is different about human anatomy, but we have a better time (better kidneys?) processing out salt. Many animals such as cats, dogs and chickens just can't process salt as well as we can and it can be really hard on their kidneys. When kidneys fail, death follows within days or even hours.