How do I know if my rats underweight?

[-Wolfie-]

I have 2 rats, ones extremely large and is on a diet the other one is rather small and lean but recently ave been thinking he may be a bit underweight. Even though he weighs 399g i don't know if this is underweight because all the other posts say different rats are different builds.

Should I be able 2 feel any bones under the skin or is this bad?

[scout]

It's okay to feel the bones under the skin, but you shouldn't be able to see his ribs sticking out and his hips shouldn't look bony. Depending on his size, 400 g can be a good weight for a male rat. If you have pictures of them, we can help you decide if he is under weight or not.

[-Wolfie-]

I can feel his bones pretty easily but you cant really see them because of his fur but i could easily count his ribs. Also i have noticed his sides heaving quite quickly even when he's just sat still, is this laboured breathing? Hes getting old now hes about 22 months, i am going to take him to the vets to see what he can suggest.

[scout]

Yep, that's labored breathing. It's hard to eat enough calories to do all the hard work to breathe, which is why he seems to be underweight. He probably is. You can add a little olive oil or cod liver oil to his diet (add it to some baby cereal) as a daily treat to add calories to his diet. Or you can supplement him with a daily dab of nutristat/nutrical available from most chain pet stores. A vet visit is an excellent idea. Sounds like he may have an upper respiratory infection. The vet can give you some antibiotics as well as a bronchodilator to help him breathe easier. If that doesn't help, he may have a heart condition and there are meds that can help that as well. Definitely make that vet appointment.