B12 is found in animal products because it's added to their diet. It doesn't come natural them. B12 you get from eating dirt, which we don't like to do.
B12 is not actually synthesized by animals, it is synthesized by bacteria. Most grain-fed livestock are heavily supplemented as well, with industrially fermented B12. You can just get the same industrially fermented B12 we inject livestock with. You don't have to inject it though.
