I have to agree with HL. I usually take my hogs for grinding. Skinned, gutted, and deboned, there just isn't that much weight left - say 30-40% MAX. I ask NOT to add beef fat to my sausage. Leaner is better for my arteries. This too decreases "yield" from the butcher.
Also, I trust my butchers. Period and without a doubt. From Day One, I trust them. My loyalty to them is dependent on that trust. They provide me with all there is that they can salvage, depending on where I shot the game. Sometimes, bullet damage is extensive. Count on some loss from that too. Trust the butcher. It is in their interest to do the best job they can on the game you bring to them. There should never be any doubt in your mind. They want to give you a quality product. One they would take home to their wife. You are going to take it home to yours.