One thing I have found with bone marrow is if you leave it out at room temp for a couple of days it gets sweet.  I thought this was a random occurrence, turned out it wasn't as I bought from another source and the same thing happened(both sources were grassfed).  Pulled it out of the freezer(yes I have a difficult time getting fresh) and let it thaw to room temp.  Had some and thought it tasted rich and creamy like a mild butter.  The following day it had a sweet taste to it and really enjoyed it.  The following day it was really sweet, it reminded me of smurfberry crunch cereal, my favorite cereal to eat as a kid.  Oh the healthy food I ate as a kid