This study found that if we converted US farmland used to grow livestock to plant proteins we could double the number of people fed.

Every study not funded by the meat or dairy industries has found similar results.

And it makes sense, logically. Eating plants directly is always going to be more efficient than feeding plants to an animal and then eating the animal - the average animal converts about ten percent of its food into biomass, so you lose roughly 90% of the plant's nutritive value.

"We feed animals the plants humans can't eat" and other such excuses work for a small farm where the chickens and pigs are part of the farm's ecosystem and return nutrition to the soil as manure. When you're talking about modern factory farming where millions of productive acres that could grow human food are used to grow animal food, it's nothing but bullshit.