The swollen leg may be from navel ill (or joint ill), an infection that enters the calves body through the umbilical cord stump. It can cause an infection in the navel area, or sometimes travels to the joints in the legs and sets up an infection there (joint ill). It will need to be treated with antibiotics. Usually shows up in calves that are about a week old. You might do a search to see what info you can find on it. Good luck with your little one -- I found your post when searching for premature calves. I am raising a little premature bull who was born 35 days early last Friday (8/5). He is doing well and is spunky, but it is an uphill battle with these little ones.