Foster kitten had rhino, now he is too thin! Help me get him to gain weight back!

[breavery]

I am fostering a siamese kitten, about 13 weeks old.. he recently had a bad case of rhino and was on 2 courses of antibiotics ... he had refused to eat and I was force feeding him for a while.. he was quite ill and lost some weight.. at this point, he is eating again but he is very thin! he is back to healthy, he's playing, eating well and "talking" as siamese like to do. My concern is that he constantly seems to be cold, always cuddling on your neck or with my dog..his paw pads are freezing... and he sits all huddled up.. he appears fragile to me! I think he needs to get back to a healthy weight to feel 100% better.
I feed him Orijen dry and EVO wet food (more wet than dry) .. I am free feeding him right now as I want him to gain weight... so, my question is this.. is there a good quality food I can feed him temporarily to help him gain his weight back? Is there a supplement I could be giving him to help him gain his weight back? I know siamese are not supposed to have the round bellies but right now I can see his bones on his hips, his ribs, etc... I just want to get him back to a healthy weight so we can get this cutie adopted into a forever home! Any advice is appreciated! Thanks

[Love4himies]

Take away all dry and feed canned only. Supplementing him with raw chicken along with the canned will help him build muscle mass faster than any commercial cat food.