One innovation changed pig farming drastically

Pigs and chickens have much in common: they eat similar diets (chickens, like pigs, are omnivorous) and grow to slaughter weight quickly -- in less than two months for chickens and less than six months for pigs. Unlike cattle, which require many leisurely months on pasture, chickens and pigs can be stuffed with feed and turned into meat in short order. Unsurprisingly, then, the agricultural methods developed for one also worked well for the other. In the 1950s and 1960s, American farmers started...