Do you think meat appears out of thin air? What do you think a farm animal (which at that point is a horribly inefficient energy converter) eats? Concern for field mice is a very good reason to go vegan.
> What do you think a farm animal (which at that point is a horribly inefficient energy converter) eats?
Pasture grazed cows eat grass, pigs can eat our food scraps, and chickens can be a great pest mitigant if allowed to graze fairly freely. You certainly don't have to get grain-fed animals from giant factory lots.
At the existing rate of consumption, you most certainly have to. At around 9 billion chicken, and 10 billion land animals in total raised and killed annually in the USA alone, the happy grazing cow, etc. is just a fantasy of an infinitesimally small number of people.
And it works, if you ignore the field mice who wind up in the giant harvesting machines.