Fancy Rats

Question
After working with animals I do know a lot about them but there is always one or two things come along that you need to seek a second opinion. I am now in my 50's  I have been keeping rats for a few years now as I have needed them for company and my new husband who has never had pets has caught the rat keeping illness. I have been unlucky the first two males had the breathing disease and both died young, the second pair seemed healthy but then I had one was put to sleep as kept having epilepsy fits and was suffering.  So Nutmeg the one who was left as is huge is now two years old now has another two for company Smokey and Chino aged 1 year.  Smokey is quiet loves cuddles and keeps sneezing but it appears to be allergies. Chino turned nasty so was castrated and since no problems. However we then saw an poor little black and white rat in Pets at Home and he was not for sale but was unwanted and needed to be adopted and money you pay went to four animal charities. Good Idea. So we got him. Raj, he is a lovely friendly little one sneezes occasionally but appears to be healthy comes out for playtime with the others and gets on well but too small to live with them yet. We are trying him out with different foods but he does not seems to eat a lot. he has a lot of loose skin on his sides to fill up he has huge great big back feet. Not sure of his age but estimate 10 weeks but may be younger. We have had him two weeks and weighed him today 5 1/2 ozs and will weigh him weekly  as we think he is under weight.  Really need ideas how I can get him to put on a little weight safely as the sooner he put on the weight the sooner he can play with the others more.

Answer
Hi,
 I have kept rats also, but also have had problems along the respiratory illness. I suggest that you take him to an exotics vet for a well rat check up. Make sure that he is not on pine or cedar bedding. I use Carefresh. I would not feed him any supplemental food or vitamins unless vet recommended. I would add some well cooked chicken and hard boiled egg yolks to his weekly meal. He needs to see an exotics vet first to make sure that everything is okay.
Ann