B12 you can get from a pill. The same stuff they inject into beef. [1]
So if you skip eating red meat, you can avoid the toxins from cooking, such as HCA and PAH [2], the exogenous cholesterol, atherosclerotic carnitine [3], hormones, etc. I think that's a better way to get B12.
If you feed cows corn all day every day, yes they need B12 injections. I buy beef from a local butcher and the beef comes from our local farm of pasture-raised cows. It's more expensive but because of this it limits my beef intake to a few times a month.
liver == steak * 1000
Only problem is being able to stomach liver a few days every month. I know it's a super food but I'll be damned if I can eat it more than once every few months.