I get whole cow femurs from the butcher, here a whole femur is about $8, they sell them by the pound. That's a whole cow legbone, from the hip joint to the hock joint. They're about 2 feet long with a big knuckle on both ends. I freeze them solid (cooked or smoked bones can splinter, raw just sort of crumble). Earnest is only allowed to have a fresh bone on his rug in the bedroom, it usually takes a day or so for it to dry out and get de-greased, then he's allowed to have them wherever he wants. He understands the command "too messy" it's funny to watch him decide which he wants to do more, come out and visit or stay in the bedroom with his bones. Here, where the climate is so dry, they last at least a month. Phyfe is bone-possesive, he's only allowed to have them for short periods and then they go back in the freezer until next time- Earnest's are stashed all over the upstairs part of the house (Phyfe lives primarily in the downstairs rooms with my son).
A friend of mine brought a new boyfriend by for me to meet, he wasn't very talkative and acted kinda weird. Later when I told her that's what I thought of him she said "he was scared, on the way home he told me he was terrified because Earnest was laying in the corner gnawing on a bone that was bigger than the bone in his (the boyfriend's) leg!"