many minerals and vitamins are fed to animals nowadays, so that in the end the "consumer of meat" gets all (s)he needs. B12 for example is normally on plants and vegetables/fruits in nature (from the bacteria living in the soil), and that is the natural way e.g. grass-fed (and all other plants growing on a pasture) animals get it in their body. vegetables/fruits etc. are nowadays washed and cleaned to make them more attractive to the customers, and so all B12 is washed off. animal science is always trying to make meat "healthier" (by fortifying the animal feeds) so "everybody" gets all vitamins and minerals necessary for their health. even animals nowadays get less vitamins and minerals naturally so that makes supplements for them too. in the end all consumers take B12 supplements - direct or second-hand.