Jerry,
The big problem with game-meat burgers "crumbling" when no fat is added is due to most people flipping them too quickly. Eileen has written about this before, but if you let them brown sufficiently on the "first side," fat-free game burgers hold together very well.
But over many years we have also both noticed that many people (especially guys) somehow think they're not really "cooking" (especially on a grill, but also in a frying pan) unless they constantly dink with the meat. Which is why it crumbles.
Have also seen this even when cooking game roasts. Many guys somehow can't resist starting to cook 'em when the grill (or indoor oven) isn't hot enough--and then turn 'em way too often. The result is pretty much gray, dry meat, all the way through. But evidently some like that....
