Dog food/performance ?

[gmanksu]

I am feeding a horseback field trial dog that I own, Enhance Professional Athlete and am pleased with the body condition that it keeps him while being worked and roaded,3-4x per week. The question is that at times it seems he gets really hot, can act like the workout is not even affecting him and breathing hard one day, lay him off for 2 days due to weather conditions (snow) and bring him back into harness and acts like he is out of shape. Has anyone had experience with this and would it be attributed to a diet issue? I have been on this workout regime for since January, only seems to be an issue is the dog has been laid off a couple days and then brought back to work. Any ideas? Thanks in advance.