[theBCnut]

One cup is too much food for my VERY active JRT. Definitely look into how many calories you are feeding. If his belly actually feels tight, it is not fat, and it can be medical emergency, so really watch that. If his belly extends and gets tight after eating, it can be a sign of liver failure, bloat, pancreatitis, or a few other serious problems. The panting/labored breathing is a sign of acute pain.