JG,
I am surprised as well, but have also had several people from southwestern Idaho say mule deer there can be bad-tasting as well, even if not rutting. Can only guess, as you do, that it's something they eat.
The only "deer" I've heard of that dogs won't eat are rutting caribou bulls, but that seems to be the consensus no matter where they're hunting. Have never encountered that myself, as all the caribou hunts I've made, from Alaska to Quebec, were from mid-August to mid-September, before the rut, sometimes before they shed their velvet.
