Chuck,
I have had similar expierences with the dogs getting the runs while hunting. I do tend to feed a bit lighter in the morning before a hunt as you might do for yourself but I do not skip feeding. They will need the fuel. I carry some buscuits for a snack during the day and give them out a few hours apart as you might do for yourself during physical exertion. Keep them hydrated with clean water. Most dogs will drink from any mud puddle or stream they come across while hunting. It is probabally not the best thing in the world for them but you are hard pressed to stop them. So between that and chocking down bird feathers It is no wonder they get the runs. Remember your dog while it may be 50 pounds it is still a puppy. He will get stronger and better able to deal with the strain of hunting as he gets older. Remember we are the intellegent ones and must know when to stop them. My dogs will run untll they die if I were to ask them to. We can't let that happen.
Bill G.