An old thread but on topic.
Got our two lambs for the season and always included are the bones. So I roasted them up and simmered in just water for 24 hours then reduced to 2.5 litres. I also got about four cups of lamb fat which I just could not throw away. We chucked the hardened disc into the bushes down by one our creeks for the bears or whoever finds it first. Good use of all the parts.