If everyone becomes a vegetarian, then what will
we do with all the farm animals?
Farm animals exist in such large numbers only because human
beings breed them for slaughter, often through artificial
insemination. As more people become vegetarian, fewer farm
animals will be bred, and their population will be reduced.
If everyone eventually becomes a vegan then the number of farm animals which will exist will only be a tiny fraction of the number today. Also, if farm land which presently grows crops for livestock was instead used to grow crops consumed directly by humans, we could feed far more people using far less land, fuel, and other resources.
Follow up questions:
Aren't the animals already dead when we purchase meat in a grocery store?