Once they're soft, I break them up and grind them in the meat grinder attachment for my mixer. Put the bones and broth in the mixer bowl with brewers' yeast, flax meal, garlic powder, a little mint, raw egg for binder, and rice flour (you can also use wheat flour or oatmeal...avoid corn meal, it gives a lot of dogs "hot spots", dry, itchy patches). You can add peanut butter if you like. Same kinds of stuff no matter what the bones came from. Mix it with the mixer, and put it back through the grinder with the large sausage tube on. Extrude the paste onto a baking sheet, cut into lengths according to dog size, and back in a slow oven, maybe 300 d. until hard. Sadie gets them about the size of my thumb. I have an old metal-body grinder attachment for my Hobart mixer, but if the bones are soft, a plastic body grinder should be OK. A hand-crank grinder works just fine, too.