Marrow has all sorts of good stuff in it. Very fatty, but good. I generally don't give marrow bones since they are very hard and can break teeth (two out of three will chew aggressively, and have broken teeth on other things, so I don't chance it), but I do scoop out some marrow for them every now and then.
Marrow, caribou marrow, is actually listed on USDA's site. It is fat with a little iron and tiny amounts of a couple other nutrients of which most dogs don't need more. Sure doesn't fill any gaps in Max's raw diet.
Fat is good for dogs but do watch how much they get of it. If your dog isn't used to eating extra fat and happens to have a wonky pancreas then marrow would be an extremely bad idea. Peanut butter actually fills a couple of gaps in Max's diet better much as I hate to admit it.
I don't give soup bones b/c they're too hard & it's too much marrow for Molly's system. Soft stools for days after the one time she was given one because all she ate was marrow. She's a smaller dog, though, at 13 lbs. It was way too much fat for her.
The marrow is very rich .....I wouldn't let them eat it all at once if you give him a large bone - I let my guy eat the whole thing & he had very loose stool for 2 days. So now, I scoop out most of it & only leave a little for him.
WHen my bf hunts he cuts up the bones for my dogs . I used to make alot of soup and when you use soup bones I know it makes the soup healthier. Lucifer has a whole thigh bone from a moose that he loves , he has been working on getting the marrow out for weeks now !!!