Not if you are vegan. If you live in a first world country, it is simply not necessary to eat meat and dairy. It is easy and cheap to eat only plants. You can get all the nutrients you need — yes including B12 and protein — from plants. You cut out the middleman, errr, “middle-species” and eat the plants the pig/cow/chicken/fish would eat. Not just by the way, not eating meat and dairy is also incredibly good for the environment, both in terms reducing land clearing for grazing, fresh water usage, and emissions reduction.