If I have a certain amount of sausage I'm making from either elk or venison, I don't add anything to the ground meat. I'll add beef fat at the time I process the ground meat into sausage. Mix in the seasonings and run it through the grinder again and then add the beef fat up to 30% depending on what I'm making. For burger, I'll usually mix it 85-90% game meat to 10-15% beef fat. I've also mixed, just before I cook a burger, some powdered dextrose or powdered milk into the burger meat...a tablespoon or so for a lb of burger. The dextrose really helps turn out a juicy burger and increases the bind as well.
I have a commercial sized grinder my dad picked up years ago that will make short work of a pile of deer or elk meat and grind for friends and add whatever they want into the venison or elk meat, they usually go with some beef fat.
If I shoot both a deer and elk, I usually make the majority of the deer into sausage and cut and grind the elk into burger, roasts and steaks. I can always circle back around, with the elk roasts and grind, either with or without the beef fat, if I choose to make some of that into some type of sausage or burger.
My wife doesn't eat pork, so over the years, with my sausage making, I've substituted beef fat for the pork butt, pork fat, etc and really, the end product IMO turns out as good or better then if I had used pork butt, fat, bacon or what have you!
