By the utilitarian argument, wouldn't the answer just be to stop eating meat and eat whatever we're feeding to livestock (or some other food grown in its place)? Meat is a pretty inefficient source of food compared to large scale agriculture.
The problem is that factory farmed animals usually eat grain which could be used to feed humans. Even if only 10% of their feed is suitable for human consumption, it's still a net loss of food, because meat is an extremely inefficient source of calories.