Almost any butcher, even at grocery stores, will hook you up with marrow bones. The key for gut health is to ask for grass fed or pastured only meat. Grass fed red meat is naturally leaner than grain-fed beef. Omega 3s in beef that feed on grass is 7% of the total fat content, compared to 1% in grain-only fed beef. Grass-fed beef has the recommended ratio of omega 6 to omega 3 fats (3:1.) It is loaded with other natural minerals and vitamins, plus it's a great source of CLA (conjugated linoleic acid) a fat that reduces the risk of cancer, obesity, diabetes, and a number of immune disorders. And, you want to make sure it is 100% pastured- no grain finishing to fatten them up!
if you're in or near to Oregon, you cannot go wrong with Rudio Creek Ranch who sells very reasonably priced beef in packs, by whole or part cow, and even sells bags of the best marrow bones I've ever seen.
- beef marrow bones- a few big ones (I just grab enough to kind of partially fill up the bottom of my crockpot)
- 2-3 big red onions, quartered (vital for tasting like something)
- 4-8 cloves minced garlic (play around with amounts, can make broth bitter if cooking for a long time or making "infinity broth")
- 1-2 TBSP olive oil
- filtered water
- 1/4 cup apple cider vinegar (This is seriously MOST important as it helps to leach minerals from the bones.)
- Optional- parsnips (can sweeten), a carrot or two, celery, shallot, seasonings like oregano
- Optional: salt & pepper (I don't add any while cooking the broth so that I can use it more universally in other recipes. So, if just drinking broth I add salt and pepper to taste. Adding smoked salt is delicious!)
Preheat oven to 425°F.
Place bones and veggies on a baking sheet and thoroughly coat in olive oil. Roast in oven for 20-30 minutes until you see just a bit of browning which will yield some color and flavor.
When roasting is finished, place all ingredients from the oven into a slow cooker. Add the apple cider vinegar, then cover all of it with water. Bring to a boil, then switch it to lowest/warm setting. Simmer for a minimum of eight hours and up to forever. OK- I'll explain that forever part next!
I like to use a combination of a large glass measuring cup, metal mesh strainer, and a Pyrex pouring bowl to harvest my broth. I simply scoop out the water with the measuring cup and pour it through the strainer into the bowl. Then, re-straining if needed, I pour the broth from the bowl into freezer safe mason jars or freezer safe containers of some kind. A disc of smooth, whit fat will rise to the top. This fat is super beneficial, so use it. If you don't drink it, then cook with it! Also, that fat creates a naturally protective barrier/seal to the broth that helps keep it fresher longer. Under that seal of tallow, there should be a nice, thick gelatin broth concentrate that you can heat up and even add water to later. It will keep in the fridge for about a week- longer if you reboil it, and for months in the freezer.
If you want to either make a marathon batch of broth from the same bones, or just keep this around all of the time, you can have a continuous broth going. Those bones and connective tissue you have there have something to offer until they are pretty much falling apart and melting away into powder. Granted, the first and second run stuff is the thickest and best, but the remaining broth is fantastically healthful, and it is great for making other soups and recipes. So, the way I do this is by harvesting as much as I can from the slow cooker without removing the bones. Then, I add more apple cider vinegar and water. Voila! As you go, you can get a feel for it and play around with replacing the veggies, adding a bone or two, taking one out as you notice it not having any marrow and tissue left, etc. And, be careful with your veggies when doing infinity broth. Some, like garlic and root veggies will turn the broth bitter somewhere between hour 24 and 36.
AND, one more thing- I also love to keep a covered ice cube tray filled with broth cubes to cook with and add a little extra flavor to greens.