When people think about not eating animal products, they often wonder: “But what would happen to all the animals?” Variations on this include, “Wouldn't farm animals go extinct?” and “Won't we be overrun by all the animals if we don't eat them?
The short answer:
Don't worry, farm animals won't go extinct or take over our cities (barring a “cows with guns” scenario).
The long answer:
All animals bred for food are slaughtered long before their natural life span, often when they are just a few weeks or months old.
That means that every year, agribusiness breeds and slaughters several entire generations of animals.
The number of animals bred into existence is directly proportional to supply and demand. When there is increased demand for meat/dairy/eggs, more animals are bred and slaughtered. When there is decreased demand, fewer animals are bred and slaughtered.
It's highly unlikely the whole world will go vegan overnight (barring some sort of vegan witchcraft). What's much more likely is that meat and dairy consumption will decline over time, so agribusiness will gradually breed and slaughter fewer animals.
In fact, we can already see this happening. There were 400 million fewer animals bred and slaughtered in 2014 compared to 2007, largely as a result of decreased demand.
Image from Mercy for Animals
If we eventually get to the point when animals are no longer bred and killed for food, there will still be cows, chickens, pigs, turkeys and goats at farm animal sanctuaries like Farm Sanctuary and Animal Place.
The bottom line: If you're concerned about farm animals going extinct, then stop eating them and donate to a farm animal sanctuary!