20% is all you need to sufficiently hold a burger together for cooking to Medium, though I sometimes use close to 40% grass fed beef mixture for making meatloaf.
Think about this: Last year at the World Squirrel Cookoff, the first place winner was a Squirrel Slider (the team deboned, ground and mixed the squirrel with fat). By the rule book, your entree has to be 80% squirrel meat. In other words, a team made a squirrel patty that won the world championship and it only contained 20% fat. If 20% if sufficient for squirrel, a much tougher meat than venison, then it is certainly a sufficient ratio for ground venison. (on a side note, I am not a fan of ground white meat).
I've had venison sausage that was mixed 50% pork fat. It didn't taste anything like venison. Don't get me wrong, it tasted good, but at some point, you might as well be eating Tennessee Pride. At the very least, it is not very accurate to call that "venison" sausage or "venison" burger, its at least as much beef or pork as it is venison. [/quote]
LOL!!
I don't profess to be a chef. I prepare my meat the way that tastes the best to me and the people I cook for. [so far I haven't had any complaints] I've tried it many ways and this is what works for me.
As far as breakfast sausage is concerned..........the spices make more difference than any amount of pork fat added. BTW, I like Jimmy Dean sausage, but mine made with venison is better.
Different strokes for different folks............