It is raspy and more labored as well as rapid. His sides seem to contract and he shows symptoms of diraheah(sp). We have also withheld food before trips to the field thinking that maybe he hadn't had ample time to digerst his meal - but that did not seem to make any differe
Well it could be laryngeal paralysis. Some of the history and symptoms fit what you typically see with this condition. But there are other possibilities as well. I would also have the heart evaluated.
Bottom line...like DocE said, I would take it to a veterinary referral center where you will find veterinary specialists who will be able to diagnose the problem.